mechanical weathering essay

• school Campus Bookshelves
• menu_book Bookshelves
• perm_media Learning Objects
• login Login
• how_to_reg Request Instructor Account
• hub Instructor Commons

Margin Size

• Download Page (PDF)
• Download Full Book (PDF)
• Periodic Table
• Physics Constants
• Scientific Calculator
• Reference & Cite
• Tools expand_more
• Readability

selected template will load here

This action is not available.

5.1: Mechanical Weathering

• Last updated
• Save as PDF
• Page ID 7799

• Steven Earle
• Vancover Island University via BCCampus

\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)

( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)

\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)

\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

\( \newcommand{\Span}{\mathrm{span}}\)

\( \newcommand{\id}{\mathrm{id}}\)

\( \newcommand{\kernel}{\mathrm{null}\,}\)

\( \newcommand{\range}{\mathrm{range}\,}\)

\( \newcommand{\RealPart}{\mathrm{Re}}\)

\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

\( \newcommand{\Argument}{\mathrm{Arg}}\)

\( \newcommand{\norm}[1]{\| #1 \|}\)

\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)

\( \newcommand{\vectorA}[1]{\vec{#1}}      % arrow\)

\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}}      % arrow\)

\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

\( \newcommand{\vectorC}[1]{\textbf{#1}} \)

\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)

\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)

\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)

Intrusive igneous rocks form at depths of several hundreds of meters to several tens of kilometers. Sediments are turned into sedimentary rocks only when they are buried by other sediments to depths in excess of several hundreds of meters. Most metamorphic rocks are formed at depths of kilometers to tens of kilometers. Weathering cannot even begin until these rocks are uplifted through various processes of mountain building—most of which are related to plate tectonics—and the overlying material has been eroded away and the rock is exposed as an outcrop . [1]

The most important agents of mechanical weathering are:

• The decrease in pressure that results from removal of overlying rock
• Freezing and thawing of water in cracks in the rock
• Formation of salt crystals within the rock
• Cracking from plant roots and removal of material by burrowing animals

When a mass of rock is exposed by weathering and removal of the overlying rock, there is a decrease in the confining pressure on the rock, and the rock expands. This unloading promotes cracking of the rock, known as exfoliation , as shown in the granitic rock in Figure \(\PageIndex{1}\)., which, in places, is peeling off like the layers of an onion.

Granitic rock tends to exfoliate parallel to the exposed surface because the rock is typically homogenous, and it doesn’t have predetermined planes along which it must fracture. Sedimentary and metamorphic rocks, on the other hand, tend to exfoliate along predetermined planes (Figure \(\PageIndex{2}\)).

Frost wedging is the process by which water seeps into cracks in a rock, expands on freezing, and thus enlarges the cracks (Figure \(\PageIndex{3}\)). The effectiveness of frost wedging is related to the frequency of freezing and thawing. Frost wedging is most effective in a climate like Canada’s. In warm areas where freezing is infrequent, in very cold areas where thawing is infrequent, or in very dry areas, where there is little water to seep into cracks, the role of frost wedging is limited. If you are ever hiking in the mountains you might hear the effects of frost wedging when the Sun warms a steep rocky slope and the fragments of rock that were pried away from the surface by freezing the night before are released as that ice melts.

In many parts of Canada, the transition between freezing nighttime temperatures and thawing daytime temperatures is frequent — tens to hundreds of times a year. Even in warm coastal areas of southern B.C., freezing and thawing transitions are common at higher elevations. A common feature in areas of effective frost wedging is a talus slope —a fan-shaped deposit of fragments removed by frost wedging from the steep rocky slopes above (Figure \(\PageIndex{4}\)).

A related process, frost heaving, takes place within unconsolidated materials on gentle slopes. In this case, water in the soil freezes and expands, pushing the overlying material up. Frost heaving is responsible for winter damage to roads all over North America.

When salt water seeps into rocks and then evaporates on a hot sunny day, salt crystals grow within cracks and pores in the rock. The growth of these crystals exerts pressure on the rock and can push grains apart, causing the rock to weaken and break. There are many examples of this on the rocky shorelines of Vancouver Island and the Gulf Islands, where sandstone outcrops are common and salty seawater is readily available (Figure \(\PageIndex{5}\)). Salt weathering can also occur away from the coast, because most environments have some salt in them.

The effects of plants and animals are significant in mechanical weathering. Roots can force their way into even the tiniest cracks, and then they exert tremendous pressure on the rocks as they grow, widening the cracks and breaking the rock (Figure \(\PageIndex{6}\)). Although animals do not normally burrow through solid rock, they can excavate and remove huge volumes of soil, and thus expose the rock to weathering by other mechanisms.

Mechanical weathering is greatly facilitated by erosion, which is the removal of weathering products, allowing for the exposure of more rock for weathering. A good example of this is shown in Figure \(\PageIndex{4}\). On the steep rock faces at the top of the cliff, rock fragments have been broken off by ice wedging, and then removed by gravity. This is a form of mass wasting, which is discussed in more detail in Chapter 15. Other important agents of erosion that also have the effect of removing the products of weathering include water in streams (Chapter 13), glacial ice (Chapter 16), and waves on the coasts (Chapter 17).

Exercise 5.1 Mechanical weathering

This photo shows granitic rock at the top of Stawamus Chief near Squamish, B.C. Identify the mechanical weathering processes that you can see taking place, or you think probably take place at this location.

See Appendix 3 for Exercise 5.1 answers .

Media Attributions

• Figures 5.1.1, 5.1.2, 5.1.3, 5.1.4, 5.1.5, 5.1.6, 5.1.7: © Steven Earle. CC BY.
• To a geologist, an outcrop is an exposure of bedrock, the solid rock of the crust. ↵

• school Campus Bookshelves
• menu_book Bookshelves
• perm_media Learning Objects
• login Login
• how_to_reg Request Instructor Account
• hub Instructor Commons

Margin Size

• Download Page (PDF)
• Download Full Book (PDF)
• Periodic Table
• Physics Constants
• Scientific Calculator
• Reference & Cite
• Tools expand_more
• Readability

selected template will load here

This action is not available.

13.2: Mechanical Weathering

• Last updated
• Save as PDF
• Page ID 5551

\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)

( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)

\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)

\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

\( \newcommand{\Span}{\mathrm{span}}\)

\( \newcommand{\id}{\mathrm{id}}\)

\( \newcommand{\kernel}{\mathrm{null}\,}\)

\( \newcommand{\range}{\mathrm{range}\,}\)

\( \newcommand{\RealPart}{\mathrm{Re}}\)

\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

\( \newcommand{\Argument}{\mathrm{Arg}}\)

\( \newcommand{\norm}[1]{\| #1 \|}\)

\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)

\( \newcommand{\vectorA}[1]{\vec{#1}}      % arrow\)

\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}}      % arrow\)

\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

\( \newcommand{\vectorC}[1]{\textbf{#1}} \)

\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)

\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)

\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)

Why is mechanical weathering so important here?

The high mountains of the Sierra Nevada are made of granite. The climate is cold. Mechanical weathering dominates the weathering here. Can you find signs of mechanical weathering in the photo? Can you see evidence of chemical weathering in the photo? Why is mechanical weathering so much more important than chemical weathering here? How is mechanical weathering altering the landscape in the high Sierra?

Mechanical Weathering

Mechanical weathering breaks rock into smaller pieces. These smaller pieces are just like the bigger rock; they're just smaller! The rock has broken without changing its composition. The smaller pieces have the same minerals in the same proportions. You could use the expression “a chip off the old block“ to describe mechanical weathering! The main agents of mechanical weathering are water, ice, and wind.

Ice Wedging

Rocks can break apart into smaller pieces in many ways. Ice wedging is common where water goes above and below its freezing point ( Figure below). This can happen in winter in the mid-latitudes or in colder climates in summer. Ice wedging is common in mountainous regions like the Sierra Nevada pictured above.

Diagram showing ice wedging.

This is how ice wedging works. When liquid water changes into solid ice, it increases in volume. You see this when you fill an ice cube tray with water and put it in the freezer. The ice cubes go to a higher level in the tray than the water. You also may have seen this if you put a can of soda into the freezer so that it cools down quickly. If you leave the can in the freezer too long, the liquid expands so much that it bends or pops the can. (For the record, water is very unusual. Most substances get smaller when they change from a liquid to a solid.)

Ice wedging happens because water expands as it goes from liquid to solid. When the temperature is warm, water works its way into cracks in rock. When the temperature cools below freezing, the water turns to ice and expands. The ice takes up more space. Over time, this wedges the rock apart. Ice wedging is very effective at weathering. You can find large piles of broken rock at the base of a slope. These rocks were broken up by ice wedging. Once loose, they tumbled down the slope.

Abrasion is another type of mechanical weathering. With abrasion, one rock bumps against another rock. Gravity causes abrasion as a rock tumbles down a slope. Moving water causes abrasion; it moves rocks so that they bump against one another ( Figure below). Strong winds cause abrasion by blasting sand against rock surfaces. Finally, the ice in glaciers cause abrasion. Pieces of rock embedded in ice at the bottom of a glacier scrape against the rock below. If you have ever collected beach glass or pebbles from a stream, you have witnessed the work of abrasion.

Water flowing through river or beach cobbles causes them to hit each other. This contact causes abrasion, which makes the rocks round.

Plants and Animals in Mechanical Weathering

Sometimes plants or animals cause mechanical weathering. This can happen slowly. A plant’s roots grow into a crack in rock. As the roots grow larger, they wedge open the crack ( Figure below ). Burrowing animals can also cause weathering. By digging for food or creating a hole to live, in the animal may break apart rock.

The large roots of this tree can break apart rock. This is mechanical weathering.

Humans and Mechanical Weathering

Today, human beings do a lot of mechanical weathering whenever we dig or blast into rock. This is common when we build homes, roads, and subways, or quarry stone for construction or other uses.

• Mechanical weathering breaks down existing rocks and minerals.
• Mechanical weathering keeps the chemical makeup of materials the same.
• Ice wedging, abrasion, and some actions of living organisms and humans bring about mechanical weathering.
• Describe the process of ice wedging. In what environment is ice wedging most likely to happen?
• Describe the process of abrasion.
• How do plants and animals cause mechanical weathering?

Explore More

Use this resource to answer the questions that follow.

• What is physical weathering?
• How do trees break down solid rock?
• What causes the most common type of physical weathering?
• What percent does water expand?
• How does water break apart a rock?

Want to create or adapt books like this? Learn more about how Pressbooks supports open publishing practices.

Chapter 5 Weathering and Soil

5.1 Mechanical Weathering

Intrusive igneous rocks form at depths of several hundreds of metres to several tens of kilometres. Sediments are turned into sedimentary rocks only when they are buried by other sediments to depths in excess of several hundreds of metres. Most metamorphic rocks are formed at depths of kilometres to tens of kilometres. Weathering cannot even begin until these rocks are uplifted through various processes of mountain building — most of which are related to plate tectonics — and the overlying material has been eroded away and the rock is exposed as an outcrop . [1]

The important agents of mechanical weathering are:

• The decrease in pressure that results from removal of overlying rock
• Freezing and thawing of water in cracks in the rock
• Formation of salt crystals within the rock
• Cracking from plant roots and exposure by burrowing animals

When a mass of rock is exposed by weathering and removal of the overlying rock, there is a decrease in the confining pressure on the rock, and the rock expands. This unloading promotes cracking of the rock, known as exfoliation , as shown in the granitic rock in Figure 5.3.

Granitic rock tends to exfoliate parallel to the exposed surface because the rock is typically homogenous, and it doesn’t have predetermined planes along which it must fracture. Sedimentary and metamorphic rocks, on the other hand, tend to exfoliate along predetermined planes (Figure 5.4).

Frost wedging is the process by which water seeps into cracks in a rock, expands on freezing, and thus enlarges the cracks (Figure 5.5). The effectiveness of frost wedging is related to the frequency of freezing and thawing. Frost wedging is most effective in a climate like Canada’s. In warm areas where freezing is infrequent, in very cold areas where thawing is infrequent, or in very dry areas, where there is little water to seep into cracks, the role of frost wedging is limited.

In many parts of Canada, the transition between freezing nighttime temperatures and thawing daytime temperatures is frequent — tens to hundreds of times a year. Even in warm coastal areas of southern B.C., freezing and thawing transitions are common at higher elevations. A common feature in areas of effective frost wedging is a talus slope — a fan-shaped deposit of fragments removed by frost wedging from the steep rocky slopes above (Figure 5.6).

A related process, frost heaving, takes place within unconsolidated materials on gentle slopes. In this case, water in the soil freezes and expands, pushing the overlying material up. Frost heaving is responsible for winter damage to roads all over North America.

When salt water seeps into rocks and then evaporates on a hot sunny day, salt crystals grow within cracks and pores in the rock. The growth of these crystals exerts pressure on the rock and can push grains apart, causing the rock to weaken and break. There are many examples of this on the rocky shorelines of Vancouver Island and the Gulf Islands, where sandstone outcrops are common and salty seawater is readily available (Figure 5.7). Salt weathering can also occur away from the coast, because most environments have some salt in them.

The effects of plants and animals are significant in mechanical weathering. Roots can force their way into even the tiniest cracks, and then they exert tremendous pressure on the rocks as they grow, widening the cracks and breaking the rock (Figure 5.8). Although animals do not normally burrow through solid rock, they can excavate and remove huge volumes of soil, and thus expose the rock to weathering by other mechanisms.

Mechanical weathering is greatly facilitated by erosion, which is the removal of weathering products, allowing for the exposure of more rock for weathering. A good example of this is shown in Figure 5.6. On the steep rock faces at the top of the cliff, rock fragments have been broken off by ice wedging, and then removed by gravity. This is a form of mass wasting, which is discussed in more detail in Chapter 15. Other important agents of erosion that also have the effect of removing the products of weathering include water in streams (Chapter 13), ice in glaciers (Chapter 16), and waves on the coasts (Chapter 17).

Exercise 5.1 Mechanical Weathering

This photo shows granitic rock at the top of Stawamus Chief near Squamish, B.C. Identify the mechanical weathering processes that you can see taking place, or you think probably take place at this location.

• To a geologist, an outcrop is an exposure of bedrock, the solid rock of the crust. ↵

Physical Geology Copyright © 2015 by Steven Earle is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

Share This Book

Erosion and Weathering

These natural forces are responsible for the shape of our environment.

Sandbars swirl beneath Oregon Inlet in Cape Hatteras National Seashore on North Carolina's Outer Banks. Waves driven by ocean winds can cause the sandbars here to shift and change literally by the hour, making conditions hazardous for boats.

The Influence of Weather

Weathering and erosion slowly chisel, polish, and buff Earth's rock into ever evolving works of art—and then wash the remains into the sea.

The processes are definitively independent, but not exclusive. Weathering is the mechanical and chemical hammer that breaks down and sculpts the rocks. Erosion transports the fragments away.

Working together they create and reveal marvels of nature from tumbling boulders high in the mountains to sandstone arches in the parched desert to polished cliffs braced against violent seas.

Water is nature's most versatile tool . For example, take rain on a frigid day. The water pools in cracks and crevices. Then, at night, the temperature drops and the water expands as it turns to ice, splitting the rock like a sledgehammer to a wedge. The next day, under the beating sun, the ice melts and trickles the cracked fragments away.

Repeated swings in temperature can also weaken and eventually fragment rock, which expands when hot and shrinks when cold. Such pulsing slowly turns stones in the arid desert to sand. Likewise, constant cycles from wet to dry will crumble clay.

Bits of sand are picked up and carried off by the wind, which can then blast the sides of nearby rocks, buffing and polishing them smooth. On the seashore, the action of waves chips away at cliffs and rakes the fragments back and forth into fine sand.

Plants and animals also take a heavy toll on Earth's hardened minerals. Lichens and mosses can squeeze into cracks and crevices, where they take root. As they grow, so do the cracks, eventually splitting into bits and pieces. Critters big and small trample, crush, and plow rocks as they scurry across the surface and burrow underground. Plants and animals also produce acids that mix with rainwater, a combination that eats away at rocks.

Precipitation

Rainwater also mixes with chemicals as it falls from the sky, forming an acidic concoction that dissolves rock. For example, acid rain dissolves limestone to form karst, a type of terrain filled with fissures, underground streams, and caves like the cenotes of Mexico's Yucatán Peninsula .

Back up on the mountains, snow and ice build up into glaciers that weigh on the rocks beneath and slowly push them downhill under the force of gravity. Together with advancing ice, the rocks carve out a path as the glacier slumps down the mountain. When the glacier begins to melt, it deposits its cargo of soil and rock, transporting the rocky debris toward the sea. Every year, rivers deposit millions of tons of sediment into the oceans.

Without the erosive forces of water, wind, and ice, rock debris would simply pile up where it forms and obscure from view nature's weathered sculptures. Although erosion is a natural process, abusive land-use practices such as deforestation and overgrazing can expedite erosion and strip the land of soils needed for food to grow.

For Hungry Minds

Related topics.

• EARTH SCIENCES
• DEFORESTATION

You May Also Like

What causes a sinkhole to form?

These breathtaking natural wonders no longer exist

What is wind chill, and how does it affect your body?

What are hurricanes, typhoons, and cyclones?

A rare and puzzling ‘domino effect’ triggered 4 powerful quakes in Afghanistan

• Paid Content
• Environment
• Photography
• Perpetual Planet

History & Culture

• History & Culture
• Mind, Body, Wonder
• Terms of Use
• Privacy Policy
• Your US State Privacy Rights
• Children's Online Privacy Policy
• Interest-Based Ads
• About Nielsen Measurement
• Do Not Sell or Share My Personal Information
• Nat Geo Home
• Attend a Live Event
• Book a Trip
• Inspire Your Kids
• Shop Nat Geo
• Visit the D.C. Museum
• Learn About Our Impact
• Support Our Mission
• Advertise With Us
• Customer Service
• Renew Subscription
• Manage Your Subscription
• Work at Nat Geo
• Sign Up for Our Newsletters
• Contribute to Protect the Planet

Copyright © 1996-2015 National Geographic Society Copyright © 2015-2024 National Geographic Partners, LLC. All rights reserved

Want to create or adapt books like this? Learn more about how Pressbooks supports open publishing practices.

28 5.1 Mechanical Weathering

Intrusive igneous rocks form at depths of several hundreds of metres to several tens of kilometres. Sediments are turned into sedimentary rocks only when they are buried by other sediments to depths in excess of several hundreds of metres. Most metamorphic rocks are formed at depths of kilometres to tens of kilometres. Weathering cannot even begin until these rocks are uplifted through various processes of mountain building—most of which are related to plate tectonics—and the overlying material has been eroded away and the rock is exposed as an outcrop . [1]

The most important agents of mechanical weathering are:

• The decrease in pressure that results from removal of overlying rock
• Freezing and thawing of water in cracks in the rock
• Formation of salt crystals within the rock
• Cracking from plant roots and removal of material by burrowing animals

When a mass of rock is exposed by weathering and removal of the overlying rock, there is a decrease in the confining pressure on the rock, and the rock expands. This unloading promotes cracking of the rock, known as exfoliation , as shown in the granitic rock in Figure 5.1.1., which, in places, is peeling off like the layers of an onion.

Granitic rock tends to exfoliate parallel to the exposed surface because the rock is typically homogenous, and it doesn’t have predetermined planes along which it must fracture. Sedimentary and metamorphic rocks, on the other hand, tend to exfoliate along predetermined planes (Figure 5.1.2).

Frost wedging is the process by which water seeps into cracks in a rock, expands on freezing, and thus enlarges the cracks (Figure 5.1.3). The effectiveness of frost wedging is related to the frequency of freezing and thawing. Frost wedging is most effective in a climate like Canada’s. In warm areas where freezing is infrequent, in very cold areas where thawing is infrequent, or in very dry areas, where there is little water to seep into cracks, the role of frost wedging is limited.  If you are ever hiking in the mountains you might hear the effects of frost wedging when the Sun warms a steep rocky slope and the fragments of rock that were pried away from the surface by freezing the night before are released as that ice melts.

In many parts of Canada, the transition between freezing nighttime temperatures and thawing daytime temperatures is frequent — tens to hundreds of times a year. Even in warm coastal areas of southern B.C., freezing and thawing transitions are common at higher elevations. A common feature in areas of effective frost wedging is a talus slope —a fan-shaped deposit of fragments removed by frost wedging from the steep rocky slopes above (Figure 5.1.4).

A related process, frost heaving, takes place within unconsolidated materials on gentle slopes. In this case, water in the soil freezes and expands, pushing the overlying material up. Frost heaving is responsible for winter damage to roads all over North America.

When salt water seeps into rocks and then evaporates on a hot sunny day, salt crystals grow within cracks and pores in the rock. The growth of these crystals exerts pressure on the rock and can push grains apart, causing the rock to weaken and break. There are many examples of this on the rocky shorelines of Vancouver Island and the Gulf Islands, where sandstone outcrops are common and salty seawater is readily available (Figure 5.1.5). Salt weathering can also occur away from the coast, because most environments have some salt in them.

The effects of plants and animals are significant in mechanical weathering. Roots can force their way into even the tiniest cracks, and then they exert tremendous pressure on the rocks as they grow, widening the cracks and breaking the rock (Figure 5.1.6). Although animals do not normally burrow through solid rock, they can excavate and remove huge volumes of soil, and thus expose the rock to weathering by other mechanisms.

Mechanical weathering is greatly facilitated by erosion, which is the removal of weathering products, allowing for the exposure of more rock for weathering. A good example of this is shown in Figure 5.1.4. On the steep rock faces at the top of the cliff, rock fragments have been broken off by ice wedging, and then removed by gravity. This is a form of mass wasting, which is discussed in more detail in Chapter 15. Other important agents of erosion that also have the effect of removing the products of weathering include water in streams (Chapter 13), glacial ice (Chapter 16), and waves on the coasts (Chapter 17).

Exercise 5.1 Mechanical weathering

This photo shows granitic rock at the top of Stawamus Chief near Squamish, B.C. Identify the mechanical weathering processes that you can see taking place, or you think probably take place at this location.

See Appendix 3 for Exercise 5.1 answers .

Media Attributions

• Figures 5.1.1, 5.1.2, 5.1.3, 5.1.4, 5.1.5, 5.1.6, 5.1.7: © Steven Earle. CC BY.
• To a geologist, an outcrop is an exposure of bedrock, the solid rock of the crust. ↵

the situation where the expansion of freezing water pries rock apart

a sloped deposit of angular rock fragments at the base of a rocky escarpment

Physical Geology - 2nd Edition Copyright © 2019 by Steven Earle is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

Share This Book

American Geosciences Institute

K-5 geosource, explore content.

• Investigations
• Literacy Strategies
• Science Fair Project

Education Resources

Profesional resources, education & outreach home, education geosource database, what is physical weathering.

Sometimes called mechanical weathering, physical weathering is the process that breaks rocks apart without changing their chemical composition. These examples illustrate physical weathering:

Swiftly moving water

Rapidly moving water can lift, for short periods of time, rocks from the stream bottom. When these rocks drop, they collide with other rocks, breaking tiny pieces off.

Ice wedging

Ice wedging causes many rocks to break. This refers to the repeated freezing and melting of water within small crevices in the rock surface. This expansion and contraction is also a major cause of potholes in streets. Water seeps into cracks in the rocks, and, as the temperature drops below freezing, the water expands as ice in the cracks. The expansion exerts tremendous pressure on the surrounding rock and acts like a wedge, making cracks wider. After repeated freezing and thawing of water, the rock breaks apart.

Plant roots

Plant roots can grow in cracks. The pressure of a confined growing root can be substantial. These pressures make cracks in the rocks larger, and, as roots grow, they can break rocks apart.

• Board of Directors
• AGI Connections Newsletter
• Nominations
• News and Announcements
• Membership Benefits
• Strategic Plan
• Annual Report
• Member Societies
• Member Society Council
• International Associates
• Trade Associates
• Academic Associates
• Regional Associates
• Liaison Organizations
• Community Documents
• Geoscience Calendar
• Center for Geoscience & Society
• Education & Outreach
• Diversity Activities
• Policy & Critical Issues
• Scholarly Information
• Geoscience Profession
• Earth Science Week
• Publication Store
• Glossary of Geology
• Earth Science Week Toolkit
• I'm a Geoscientist
• Free Geoscience Resources
• AGI Connections
• Be a Visiting Geoscientist
• Use Our Workspace

• Science Notes Posts
• Contact Science Notes
• Todd Helmenstine Biography
• Anne Helmenstine Biography
• Free Printable Periodic Tables (PDF and PNG)
• Periodic Table Wallpapers
• Interactive Periodic Table
• Periodic Table Posters
• How to Grow Crystals
• Chemistry Projects
• Fire and Flames Projects
• Holiday Science
• Chemistry Problems With Answers
• Physics Problems
• Unit Conversion Example Problems
• Chemistry Worksheets
• Biology Worksheets
• Periodic Table Worksheets
• Physical Science Worksheets
• Science Lab Worksheets
• My Amazon Books

Weathering – Physical, Chemical, Biological

Weathering is a geological process that naturally breaks down rocks and minerals at or near the Earth’s surface. It occurs over time scales ranging from years to millennia. Weathering plays a pivotal role in shaping the Earth’s landscapes and influencing the cycling of nutrients and elements. This process differs from erosion, which involves the physical removal and transport of material by agents such as water, wind, or ice.

Types of Weathering

There are two broad types of weathering: physical (or mechanical) and chemical weathering. Sometimes biological weathering is considered a separate type, but more often it gets included in the two main categories.

Examples of Physical and Chemical Weathering

Arches National Park is a result of salt and frost weathering (physical weathering). The rounded hills of the Appalachians result largely from chemical weathering processes.

Physical Weathering

Also known as mechanical weathering, physical weathering involves the breakdown of rocks and minerals into smaller pieces without changing their chemical composition. Various environmental factors drive this process, including temperature fluctuations, pressure changes , and biological activity.

Frost Weathering

Frost weathering or freeze-thaw weathering occurs in regions with temperature fluctuations around the freezing point. Water enters cracks in rocks, freezes, and expands, exerting pressure that enlarges the cracks and eventually fragments the rock.

Thermal Stress Weathering

Thermal stress weathering results from extreme temperature changes. This is common in desert environments. Rocks expand when heated and contract when cooled. Repeated cycles cause stress and eventual fracturing.

Pressure Release or Unloading

Pressure release weathering happens when overlying rock layers erode away, reducing the pressure on underlying rocks. Lowering the pressure makes the rock expand and fracture parallel to the surface. Granite domes are an example of a feature that results from this process.

Salt Weathering

Salt weathering is common in arid and coastal regions. Salty water evaporates the salt crystallizes in rock pores and cracks. As the salt crystals grow, they exert pressure on the rock and break it. Note that while sodium chloride is a common salt , other chemical compositions are important, too.

Biological Contributions

Plants and animals also contribute to physical weathering. Roots growing into rock crevices exert pressure and cause mechanical fracturing. Burrowing animals move rocks and aid in their breakdown.

Chemical Weathering

Chemical weathering involves the chemical alteration of minerals within rocks, forming new minerals and soluble salts. This type of weathering contributes to soil formation.

Dissolution

Dissolution is the process where minerals dissolve in water. Carbonate rocks like limestone are particularly susceptible, leading to karst landscapes with features like sinkholes and caves.

Hydrolysis is the reaction of minerals with water, forming new minerals and releasing ions. This process is essential in breaking feldspar minerals into clay.

Carbonation

Carbonation occurs when carbon dioxide dissolves in water and forms weak carbonic acid. The acid reacts with minerals like calcium carbonate in rocks and breaks them up.

Oxidation involves the reaction between minerals and oxygen. It commonly occurs as rusting in iron-rich rocks. This process weakens rocks and changes their composition.

Hydration is the absorption of water into the crystal structure of minerals. This makes them expand and weaken. This is distinct from simple wetting.

Plants, fungi , and bacteria contribute to chemical weathering through the production of organic acids which enhance mineral breakdown. Bird droppings and bat guano and the chemicals released by lichens also cause chemical weathering.

Factors Influencing Weathering Rates

Several factors influence the rate of weathering:

• Climate : Temperature and precipitation patterns heavily influence both physical and chemical weathering processes.
• Rock Type : Different rock types have varying susceptibilities to weathering.
• Topography : Slope and aspect affect moisture retention and exposure to environmental forces, influencing weathering rates.
• Vegetation : Plant roots and organic acid production accelerate both physical and chemical weathering.
• Time : The duration of exposure to weathering processes affects the extent of rock degradation.

Where Do the Types of Weathering Occur?

Physical weathering is prevalent in arid and cold climates. For example, thermal stress and frost weathering are dominant processes in deserts and high mountain regions. Chemical weathering is more significant in warm, humid climates. For example, abundant rainfall and high temperatures accelerate chemical reactions in tropical rainforests.

Weathering of Manmade Structures

Similar to natural geological processes, the weathering of buildings, statues, and other manmade structures involves both physical and chemical mechanisms. Human activities and environmental pollution often accelerate these processes.

Physical Weathering of Human-Made Structures

Physical weathering in human-made structures occurs due to various factors:

• Thermal Expansion and Contraction : Materials expand when heated and contract when cooled. This causes cracking and spalling in materials like concrete and brick.
• Frost Weathering : Water entering cracks and pores in materials freezes and expand, similar to frost weathering in natural rocks. This deteriorates masonry and stonework in cold climates.
• Salt Crystallization : Salt accumulates in the pores of materials in coastal areas or where de-icing salts are used. Crystallization of these salts exerts pressure and causes disintegration of the material.
• Mechanical Erosion : Wind-driven sand and other particles erode the surfaces of buildings and statues, gradually wearing them down or smoothing their features.

Chemical Weathering of Human-Made Structures

Chemical weathering also plays a significant role in the degradation of human-made structures:

• Acid Rain : Pollutants like sulfur dioxide and nitrogen oxides in the atmosphere combine with water vapor to form weak acids. When acid rain falls on buildings and statues, it causes significant chemical weathering through dissolution and surface erosion. Limestone and marble are particularly susceptible to acid rain.
• Oxidation : Metal components of structures, such as iron reinforcements or bronze statues, are susceptible to oxidation (rusting). Oxidation is especially common in humid environments. It weakens structural integrity and causes aesthetic damage.
• Carbonation : Carbonation of concrete is where calcium hydroxide reacts with carbon dioxide to form calcium carbonate. This leads to a reduction in pH and corrodes steel reinforcement, compromising structural integrity.
• Pollution : Urban environments often have higher concentrations of corrosive pollutants, which accelerate the chemical degradation of building materials.

Biological Weathering

Biological factors also contribute to the weathering of human-made structures:

• Microbial and Algal Growth : Microorganisms and algae grow on surfaces, especially in damp conditions. This causes discoloration and potential physical damage. Chemical damage also occurs when organisms produces acidic compounds.
• Root Damage : Roots from nearby vegetation grow into cracks and crevices. This causes physical disruption and sometimes introduces moisture and organic acids.

Prevention and Conservation

Various strategies mitigate weathering of human-made structures:

• Material Selection and Design : Choosing weather-resistant materials and designing structures to minimize water retention and thermal stress reduces weathering.
• Protective Coatings : Applying water repellents, anti-graffiti coatings, or corrosion inhibitors protect against weathering processes.
• Regular Maintenance : Regular cleaning, repairing cracks, repointing masonry, and removing vegetation help prevent or slow down weathering.
• Environmental Controls : Reducing pollution or acid rain reduces the impacts on structures.
• Blatt, Harvey; Tracy, Robert J. (1996). Petrology : Igneous, Sedimentary, and Metamorphic (2nd ed.). New York: W.H. Freeman. ISBN 0716724383.
• Fry, E. Jennie (1927). “The Mechanical Action of Crustaceous Lichens on Substrata of Shale, Schist, Gneiss, Limestone, and Obsidian”. Annals of Botany . os-41 (3): 437–460. doi: 10.1093/oxfordjournals.aob.a090084
• Hall, Kevin (1999). “The role of thermal stress fatigue in the breakdown of rock in cold regions”. Geomorphology . 31 (1–4): 47–63. doi: 10.1016/S0169-555X(99)00072-0
• Murton, J. B.; Peterson, R.; Ozouf, J.-C. (2006). “Bedrock Fracture by Ice Segregation in Cold Regions”. Science . 314 (5802): 1127–1129. doi: 10.1126/science.1132127
• Zambell, C.B.; Adams, J.M.; Gorring, M.L.; Schwartzman, D.W. (2012). “Effect of lichen colonization on chemical weathering of hornblende granite as estimated by aqueous elemental flux”. Chemical Geology . 291: 166–174. doi: 10.1016/j.chemgeo.2011.10.009

Related Posts

Weathering describes the breaking down or dissolving of rocks and minerals on the surface of Earth. Water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering.

Earth Science, Geology, Geography, Physical Geography

Loading ...

Weathering describes the breaking down or dissolving of rocks and minerals on the surface of Earth. Water, ice, acids , salts , plants, animals, and changes in temperature are all agents of weathering. Once a rock has been broken down, a process called erosion transports the bits of rock and mineral away. No rock on Earth is hard enough to resist the forces of weathering and erosion. Together, these processes carved landmarks such as the Grand Canyon , in the U.S. state of Arizona. This massive canyon is 446 kilometers (277 miles) long, as much as 29 kilometers (18 miles) wide, and 1.6 kilometers (one mile) deep.

Weathering and erosion constantly change the rocky landscape of Earth. Weathering wears away exposed surfaces over time. The length of exposure often contributes to how vulnerable a rock is to weathering. Rocks, such as lavas , that are quickly buried beneath other rocks are less vulnerable to weathering and erosion than rocks that are exposed to agents such as wind and water.

As it smooths rough, sharp rock surfaces, weathering is often the first step in the production of soils . Tiny bits of weathered minerals mix with plants, animal remains , fungi, bacteria, and other organisms. A single type of weathered rock often produces in fertile soil, while weathered materials from a collection of rocks is richer in mineral diversity and contributes to more fertile soil. Soils types associated with a mixture of weathered rock include glacial till , loess , and alluvial sediments .

Weathering is often divided into the processes of mechanical weathering and chemical weathering . Biological weathering , in which living or once-living organisms contribute to weathering, can be a part of both processes.

Mechanical Weathering 

Mechanical weathering, also called physical weathering and disaggregation , causes rocks to crumble. Water, in either liquid or solid form, is often a key agent of mechanical weathering. For instance, liquid water can seep into cracks and crevices in rock. If temperatures drop low enough, the water will freeze . When water freezes, it expands . The ice then works as a wedge . It slowly widens the cracks and splits the rock. When ice melts, liquid water performs the act of erosion by carrying away the tiny rock fragments lost in the split. This specific process (the freeze-thaw cycle) is called frost weathering or cryofracturing .

Temperature changes can also contribute to mechanical weathering in a process called thermal stress . Changes in temperature cause rock to expand (with heat) and contract (with cold). As this happens over and over again, the structure of the rock weakens. Over time, it crumbles. Rocky desert landscapes are particularly vulnerable to thermal stress. The outer layer of desert rocks undergo repeated stress as the temperature changes from day to night. Eventually, outer layers flake off in thin sheets, a process called exfoliation . Exfoliation contributes to the formation of  bornhardts , one of the most dramatic features in landscapes formed by weathering and erosion. Bornhardts are tall, domed, isolated rocks often found in tropical areas. Sugarloaf Mountain, an iconic landmark in Rio de Janeiro, Brazil, is a bornhardt.

Changes in pressure can also contribute to exfoliation due to weathering. In a process called unloading, overlying materials are removed. The underlying rocks, released from overlying pressure, can then expand. As the rock surface expands, it becomes vulnerable to fracturing in a process called sheeting .

Another type of mechanical weathering occurs when clay or other materials near rock absorb water. Clay, more porous than rock, can swell with water, weathering the surrounding, harder rock. Salt also works to weather rock in a process called haloclasty . Saltwater sometimes gets into the cracks and pores of rock. If the saltwater evaporates , salt crystals are left behind. As the crystals grow, they put pressure on the rock, slowly breaking it apart. Honeycomb weathering is associated with haloclasty. As its name implies, honeycomb weathering describes rock formations with hundreds or even thousands of pits formed by the growth of salt crystals. Honeycomb weathering is common in coastal areas, where sea sprays constantly force rocks to interact with salts.

Haloclasty is not limited to coastal landscapes. Salt upwelling , the geologic process in which underground salt domes expand, can contribute to weathering of the overlying rock. Structures in the ancient city of Petra, Jordan, were made unstable and often collapsed due to salt upwelling from the ground below.

Plants and animals can be agents of mechanical weathering. The seed of a tree may sprout in soil that has collected in a cracked rock. As the roots grow, they widen the cracks, eventually breaking the rock into pieces. Over time, trees can break apart even large rocks. Even small plants, such as mosses, can enlarge tiny cracks as they grow. Animals that tunnel underground, such as moles and prairie dogs, also work to break apart rock and soil. Other animals dig and trample rock aboveground, causing rock to slowly crumble. 

Chemical Weathering

Chemical weathering changes the molecular structure of rocks and soil. For instance, carbon dioxide from the air or soil sometimes combines with water in a process called carbonation . This produces a weak acid, called carbonic acid , that can dissolve rock. Carbonic acid is especially effective at dissolving limestone . When carbonic acid seeps through limestone underground, it can open up huge cracks or hollow out vast networks of caves . Carlsbad Caverns National Park, in the U.S. state of New Mexico, includes more than 119 limestone caves created by weathering and erosion. The largest is called the Big Room. With an area of about 33,210 square meters (357,469 square feet), the Big Room is the size of six football fields.

Sometimes, chemical weathering dissolves large portions of limestone or other rock on the surface of Earth to form a landscape called karst . In these areas, the surface rock is pockmarked with holes, sinkholes , and caves. One of the world’s most spectacular examples of karst is Shilin, or the Stone Forest, near Kunming, China. Hundreds of slender, sharp towers of weathered limestone rise from the landscape.

Another type of chemical weathering works on rocks that contain iron. These rocks turn to rust in a process called oxidation . Rust is a compound created by the interaction of oxygen and iron in the presence of water. As rust expands, it weakens rock and helps break it apart.

Hydration is a form of chemical weathering in which the chemical bonds of the mineral are changed as it interacts with water. One instance of hydration occurs as the mineral anhydrite reacts with groundwater . The water transforms anhydrite into gypsum , one of the most common minerals on Earth.

Another familiar form of chemical weathering is hydrolysis . In the process of hydrolysis, a new solution (a mixture of two or more substances) is formed as chemicals in rock interact with water. In many rocks, for example, sodium minerals interact with water to form a saltwater solution.

Hydration and hydrolysis contribute to flared slopes , another dramatic example of a landscape formed by weathering and erosion. Flared slopes are concave rock formations sometimes nicknamed “wave rocks.” Their c-shape is largely a result of subsurface weathering, in which hydration and hydrolysis wear away rocks beneath the landscape’s surface.

Living or once-living organisms can also be agents of chemical weathering. The decaying remains of plants and some fungi form carbonic acid, which can weaken and dissolve rock. Some bacteria can weather rock in order to access nutrients such as magnesium or potassium. Clay minerals, including quartz , are among the most common byproducts of chemical weathering. Clays make up about 40 percent of the chemicals in all sedimentary rocks on Earth.

Weathering and People

Weathering is a natural process, but human activities can speed it up. For example, certain kinds of air pollution increase the rate of weathering. Burning coal , natural gas , and petroleum releases chemicals such as nitrogen oxide and sulfur dioxide into the atmosphere . When these chemicals combine with sunlight and moisture, they change into acids. They then fall back to Earth as acid rain . Acid rain rapidly weathers limestone, marble , and other kinds of stone. The effects of acid rain can often be seen on gravestones , making names and other inscriptions impossible to read. Acid rain has also damaged many historic buildings and monuments . For example, at 71 meters (233 feet) tall, the Leshan Giant Buddha at Mount Emei, China is the world’s largest statue of the Buddha. It was carved 1,300 years ago and sat unharmed for centuries. An innovative drainage system mitigates the natural process of erosion. But in recent years, acid rain has turned the statue’s nose black and made some of its hair crumble and fall.

Spheroidal Weathering

Spheroidal weathering is a form of chemical weathering that occurs when a rectangular block is weathered from three sides at the corners and from two sides along its edges. It is also called “onion skin” weathering.

Weathered Mountains

The Appalachian Mountains in eastern North America once towered more than 9,000 meters (30,000 feet) high—taller than Mount Everest! Over millions of years, weathering and erosion have worn them down. Today, the highest Appalachian peak reaches just 2,037 meters (6,684 feet) high.

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Last Updated

April 24, 2024

User Permissions

For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.

If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.

Text on this page is printable and can be used according to our Terms of Service .

Interactives

Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.

Related Resources

• 0 Shopping Cart

What is chemical and mechanical weathering?

Weathering is the break down of rock in situ (where they are)

What is weathering?

Weathering is the breakup and breakdown of rock in situ by the action of rainwater, extremes of temperature, and biological activity.

What is mechanical weathering?

Mechanical weathering is the breakup of rock without changing its chemical composition. This means the rock breaks up without its chemical makeup changing. Freeze-thaw weathering is the primary type of mechanical weathering that affects coasts.

Freeze-thaw weathering occurs when rocks are porous (contain holes) or permeable (allow water to pass through). W ater enters the rock and freezes. The ice expands by around 9%. This causes pressure on the rock until it cracks. Repeated freeze-thaw can cause the rock to break up.

Freeze-thaw weathering

Recently weathered rock can be seen at the foot of chalk and limestone cliffs and is easily identified because it is angular. Over time it will become smoother, forming peddles and then eventually sand.

Biological weathering involves the roots of vegetation, causing the breakup of rocks.

Biological weathering at the coast

Salt weathering is when salt spray from the sea gets into a crack in a rock. Water then evaporates, depositing salt crystals that expand when heated, putting pressure on the surrounding rock and weakening the structure.

The end product can be granules or blocks of rock. Salt crystallisation also forms rock holes called honeycombs or cave-like depressions called tafoni.

What is chemical weathering?

Chemical weathering is the breakdown of rock by changing its chemical composition. When rainwater hits a rock, it decomposes it or eats it away. This is known as carbonation. This occurs when slightly acidic (carbonic) rain or sea water comes into contact with sedimentary rock, such as limestone or chalk, and it causes it to dissolve. A chemical reaction occurs between the acidic water and calcium carbonate, forming calcium bicarbonate. This is soluble and is carried away in solution. Carbonation weathering happens in warm, wet conditions.

Hydrolysis is when acidic rainwater breaks down the rock, causing it to rot.

Oxidation is when rocks are broken down by oxygen and water.

Weathering weakens cliffs, and this then speeds up rates of erosion .

Premium Resources

Please support internet geography.

If you've found the resources on this page useful please consider making a secure donation via PayPal to support the development of the site. The site is self-funded and your support is really appreciated.

Related Topics

Use the images below to explore related GeoTopics.

Constructive Waves

Destructive Waves

Mass Movement

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)
• Click to share on Pinterest (Opens in new window)
• Click to email a link to a friend (Opens in new window)
• Click to share on WhatsApp (Opens in new window)
• Click to print (Opens in new window)

If you've found the resources on this site useful please consider making a secure donation via PayPal to support the development of the site. The site is self-funded and your support is really appreciated.

Search Internet Geography

Top posts and pages.

Latest Blog Entries

Pin It on Pinterest

• Click to share
• Print Friendly

• Earth Science

Mechanical Weathering

Rocks are the natural source of materials, and there are many types of rocks in nature. There are many types of rock in nature being sourced by geologists. Rocks are solid crystals formed by various minerals which have been fused together to a significant mass of solid. Rock takes millions of years to form a rock, and it further takes many years to undergo changes.

Rocks undergo a process known as weathering. Weathering is the process of breaking down or dissolving rocks and minerals on the surface of the Earth. There are four types of weathering:

• Chemical weathering
• Physical weathering
• Biological weathering
• Mechanical weathering

In this article, let us know in detail about the mechanical weathering process.

What Is Mechanical Weathering?

Rocks break due to various reasons like wind, ice, weather, water, acids and chemical reactions. Even if an external force like the growing of plants takes place on rocks, the roots lead to weathering. Let’s see how mechanical weathering takes place.

Mechanical weathering is also known as physical weathering. In this type of weathering, a large rock is disintegrated into smaller pieces of rocks. When rocks disintegrate or break up without experiencing any change in their chemical composition, it is known as mechanical weathering. Thermal expansion and contraction that happens due to the increase or decrease in temperature. This process causes the rock to break into fragments.

Types of Mechanical Weathering

There are two main types of mechanical weathering:

• Freeze-thaw weathering or Frost Wedging
• Exfoliation weathering or Unloading
• Thermal Expansion
• Abrasion and Impact
• Salt weathering or Haloclasty

Let us see in detail about each type of weathering.

Freeze-Thaw Weathering or Frost Wedging

Frost Wedging occurs when water seeps into cracks of the rocks, freezes and expands, gradually breaking the rock apart into pieces. This expansion leads to the cracking of the rocks from inside and eventually breaks them apart. The freeze-thaw cycle happens repeatedly and finally breaks the rock, and hence it is called Freeze-thaw weathering.

Exfoliation Weathering or Unloading

This type of weathering takes place when the cracks develop parallel to the land surface. As a result, a consequence of the reduction in pressure takes place during uplift and erosion. In exfoliation, rock breaks apart in layers that are parallel to the Earth’s surface. Exfoliation is common in plutonic igneous rocks since they are exposed to great pressure.

Heating and cooling of rocks repeatedly result in the expansion and contraction of the rock. When rock is exposed to high temperatures, it expands and as the temperatures cool, it contracts. This continual expansion and contraction cause the rocks to weaken and eventually break into pieces. Thermal expansion weathering is similar to Freeze-Thaw weathering.

Abrasion Weathering

When a rock collides with one another, grinding of rock fragments takes place, and the rock is broken into pieces. Abrasion cuts them into smaller particles. Gravity causes abrasion when the rocks tumble down a mountainside and hit another rock, and break into the fragment. Moving water causes abrasion as particles in the water collide and bump against one another. High-speed winds which carry pieces of sand have the capacity to break the rock when they sandblast on the surface of the rock. Abrasion makes rocks with sharp or jagged edges round-shaped and smooth.

Salt Weathering or Haloclasty

Salt Weathering or Haloclasty is the process by which saline solutions enter the cracks in a rock and evaporate, leaving behind salt crystals. When the temperatures rise, the accumulated salt crystals get heated and start to expand and release pressure on the rock, causing it to break.

Factors Affecting Mechanical Weathering

Some of the factors that are responsible for mechanical weathering are:

• Growth of plants on the rock.
• Temperature and pressure changes in nature.
• Freezing and thawing of water in cracks of the rock.
• Formation of salt crystals within the rock.
• Burrowing by animals.

Related links

Stay tuned with BYJU’S for more such interesting articles. Also, register to “BYJU’S – The Learning App” for loads of interactive, engaging Physics-related videos and an unlimited academic assist.

Frequently Asked Questions – FAQs

What is weathering.

Weathering is the process of breaking down or dissolving of rocks and minerals on the surface of the Earth.

What are the types of mechanical weathering?

The following are the types of mechanical weathering:

What are the types of weathering?

Types of weathering are:

Does growth of plants on the rock cause mechanical weathering?

What is mechanical weathering.

When rocks break without experiencing any change in their chemical composition, it is known as mechanical weathering.

Different Types of Rocks and its Formation

Leave a Comment Cancel reply

Your Mobile number and Email id will not be published. Required fields are marked *

Request OTP on Voice Call

Post My Comment

• Share Share

Register with BYJU'S & Download Free PDFs

Register with byju's & watch live videos.

Weathering & Mass Movement

What are the 2 types of weathering.

Weathering describes the natural processes that break down rocks. There are 2 main types of weathering - mechanical weathering and chemical weathering.

Mechanical weathering

• The chemical composition of rock stays the same in mechanical weathering (also called physical weathering).
• Water expands when it freezes causing the crack to get wider and deeper.
• When the ice melts, there is now a larger crack that fills with water and then freezes again.
• This process of freezing and melting (known as thawing) can cause significant erosion on coastlines over time.

Chemical weathering

• In chemical weathering, the chemical composition of rock changes.
• When the climate is warm and wet, carbon dioxide can dissolve in rain to create a 'carbonic acid'.
• The carbonic acid in rainfall hits rocks and dissolves the parts of the rock made of calcium carbonate.
• This also breaks down rock.

Mass Movement

Mass movement describes the large movement of soil and rock down the slope of a hill or cliff.

What causes mass movements?

• Mass movements are caused by weathering, erosion, and gravity.
• Small changes over time can mean that the centre of gravity of a cliff can hang over the sea, instead of over land making the cliff unstable and prone to mass movement.

• Rockfalls are when the cliff (materials) break and crumble down the cliff.

• Slides are when material moves down a slope in a straight line.

• Slumps are when material moves down a slope at a curve.

1 The Challenge of Natural Hazards

1.1 Natural Hazards

1.1.1 Types of Natural Hazards

1.1.2 Hazard Risk

1.1.3 Consequences of Natural Hazards

1.1.4 End of Topic Test - Natural Hazards

1.1.5 Exam-Style Questions - Natural Hazards

1.2 Tectonic Hazards

1.2.1 Tectonic Plates

1.2.2 Tectonic Plates & Convection Currents

1.2.3 Plate Margins

1.2.4 Volcanoes

1.2.5 Effects of Volcanoes

1.2.6 Responses to Volcanic Eruptions

1.2.7 Earthquakes

1.2.8 Earthquakes 2

1.2.9 Responses to Earthquakes

1.2.10 Case Studies: The L'Aquila & Kashmir Earthquakes

1.2.11 Earthquake Case Study: Chile 2010

1.2.12 Earthquake Case Study: Nepal 2015

1.2.13 Living with Tectonic Hazards 1

1.2.14 Living with Tectonic Hazards 2

1.2.15 End of Topic Test - Tectonic Hazards

1.2.16 Exam-Style Questions - Tectonic Hazards

1.2.17 Tectonic Hazards - Statistical Skills

1.3 Weather Hazards

1.3.1 Global Atmospheric Circulation

1.3.2 Surface Winds

1.3.3 UK Weather Hazards

1.3.4 Tropical Storms

1.3.5 Features of Tropical Storms

1.3.6 Impact of Tropical Storms 1

1.3.7 Impact of Tropical Storms 2

1.3.8 Tropical Storms Case Study: Katrina

1.3.9 Tropical Storms Case Study: Haiyan

1.3.10 UK Weather Hazards Case Study: Somerset 2014

1.3.11 End of Topic Test - Weather Hazards

1.3.12 Exam-Style Questions - Weather Hazards

1.3.13 Weather Hazards - Statistical Skills

1.4 Climate Change

1.4.1 Evidence for Climate Change

1.4.2 Causes of Climate Change

1.4.3 Effects of Climate Change

1.4.4 Managing Climate Change

1.4.5 End of Topic Test - Climate Change

1.4.6 Exam-Style Questions - Climate Change

1.4.7 Climate Change - Statistical Skills

2 The Living World

2.1 Ecosystems

2.1.1 Ecosystems

2.1.2 Ecosystem Cascades & Global Ecosystems

2.1.3 Ecosystem Case Study: Freshwater Ponds

2.2 Tropical Rainforests

2.2.1 Tropical Rainforests - Intro & Interdependence

2.2.2 Adaptations

2.2.3 Biodiversity of Tropical Rainforests

2.2.4 Deforestation

2.2.5 Case Study: Deforestation in the Amazon Rainforest

2.2.6 Sustainable Management of Rainforests

2.2.7 Case Study: Malaysian Rainforest

2.2.8 End of Topic Test - Tropical Rainforests

2.2.9 Exam-Style Questions - Tropical Rainforests

2.2.10 Deforestation - Statistical Skills

2.3 Hot Deserts

2.3.1 Overview of Hot Deserts

2.3.2 Biodiversity & Adaptation to Hot Deserts

2.3.3 Case Study: Sahara Desert

2.3.4 Desertification

2.3.5 Case Study: Thar Desert

2.3.6 End of Topic Test - Hot Deserts

2.3.7 Exam-Style Questions - Hot Deserts

2.4 Tundra & Polar Environments

2.4.1 Overview of Cold Environments

2.4.2 Adaptations in Cold Environments

2.4.3 Biodiversity in Cold Environments

2.4.4 Case Study: Alaska

2.4.5 Sustainable Management

2.4.6 Case Study: Svalbard

2.4.7 End of Topic Test - Tundra & Polar Environments

2.4.8 Exam-Style Questions - Cold Environments

3 Physical Landscapes in the UK

3.1 The UK Physical Landscape

3.1.1 The UK Physical Landscape

3.2 Coastal Landscapes in the UK

3.2.1 Types of Wave

3.2.2 Weathering & Mass Movement

3.2.3 Processes of Erosion & Wave-Cut Platforms

3.2.4 Headlands, Bays, Caves, Arches & Stacks

3.2.5 Transportation

3.2.6 Deposition

3.2.7 Spits, Bars & Sand Dunes

3.2.8 Case Study: Landforms on the Dorset Coast

3.2.9 Types of Coastal Management 1

3.2.10 Types of Coastal Management 2

3.2.11 Coastal Management Case Study - Holderness

3.2.12 Coastal Management Case Study: Swanage

3.2.13 Coastal Management Case Study - Lyme Regis

3.2.14 End of Topic Test - Coastal Landscapes in the UK

3.2.15 Exam-Style Questions - Coasts

3.3 River Landscapes in the UK

3.3.1 The River Valley

3.3.2 River Valley Case Study - River Tees

3.3.3 Erosion

3.3.4 Transportation & Deposition

3.3.5 Waterfalls, Gorges & Interlocking Spurs

3.3.6 Meanders & Oxbow Lakes

3.3.7 Floodplains & Levees

3.3.8 Estuaries

3.3.9 Case Study: The River Clyde

3.3.10 River Management

3.3.11 Hard & Soft Flood Defences

3.3.12 River Management Case Study - Boscastle

3.3.13 River Management Case Study - Banbury

3.3.14 End of Topic Test - River Landscapes in the UK

3.3.15 Exam-Style Questions - Rivers

3.4 Glacial Landscapes in the UK

3.4.1 Erosion

3.4.2 Landforms Caused by Erosion

3.4.3 Landforms Caused by Transportation & Deposition

3.4.4 Snowdonia

3.4.5 Land Use in Glaciated Areas

3.4.6 Tourism in Glacial Landscapes

3.4.7 Case Study - Lake District

3.4.8 End of Topic Test - Glacial Landscapes in the UK

3.4.9 Exam-Style Questions - Glacial Landscapes

4 Urban Issues & Challenges

4.1 Urban Issues & Challenges

4.1.1 Urbanisation

4.1.2 Urbanisation Case Study: Lagos

4.1.3 Urbanisation Case Study: Rio de Janeiro

4.1.4 UK Cities

4.1.5 Case Study: Urban Regen Projects - Manchester

4.1.6 Case Study: Urban Change in Liverpool

4.1.7 Case Study: Urban Change in Bristol

4.1.8 Sustainable Urban Life

4.1.9 End of Topic Test - Urban Issues & Challenges

4.1.10 Exam-Style Questions - Urban Issues & Challenges

4.1.11 Urban Issues -Statistical Skills

5 The Changing Economic World

5.1 The Changing Economic World

5.1.1 Measuring Development

5.1.2 Classifying Countries Based on Wealth

5.1.3 The Demographic Transition Model

5.1.4 Physical & Historical Causes of Uneven Development

5.1.5 Economic Causes of Uneven Development

5.1.6 How Can We Reduce the Global Development Gap?

5.1.7 Case Study: Tourism in Kenya

5.1.8 Case Study: Tourism in Jamaica

5.1.9 Case Study: Economic Development in India

5.1.10 Case Study: Aid & Development in India

5.1.11 Case Study: Economic Development in Nigeria

5.1.12 Case Study: Aid & Development in Nigeria

5.1.13 Economic Development in the UK

5.1.14 Economic Development UK: Industry & Rural

5.1.15 Economic Development UK: Transport & North-South

5.1.16 Economic Development UK: Regional & Global

5.1.17 End of Topic Test - The Changing Economic World

5.1.18 Exam-Style Questions - The Changing Economic World

5.1.19 Changing Economic World - Statistical Skills

6 The Challenge of Resource Management

6.1 Resource Management

6.1.1 Global Distribution of Resources

6.1.2 Food in the UK

6.1.3 Water in the UK 1

6.1.4 Water in the UK 2

6.1.5 Energy in the UK

6.1.6 Resource Management - Statistical Skills

6.2.1 Areas of Food Surplus & Food Deficit

6.2.2 Food Supply & Food Insecurity

6.2.3 Increasing Food Supply

6.2.4 Case Study: Thanet Earth

6.2.5 Creating a Sustainable Food Supply

6.2.6 Case Study: Agroforestry in Mali

6.2.7 End of Topic Test - Food

6.2.8 Exam-Style Questions - Food

6.2.9 Food - Statistical Skills

6.3.1 The Global Demand for Water

6.3.2 What Affects the Availability of Water?

6.3.3 Increasing Water Supplies

6.3.4 Case Study: Water Transfer in China

6.3.5 Sustainable Water Supply

6.3.6 Case Study: Kenya's Sand Dams

6.3.7 Case Study: Lesotho Highland Water Project

6.3.8 Case Study: Wakel River Basin Project

6.3.9 Exam-Style Questions - Water

6.3.10 Water - Statistical Skills

6.4.1 Global Demand for Energy

6.4.2 Factors Affecting Energy Supply

6.4.3 Increasing Energy Supply: Renewables

6.4.4 Increasing Energy Supply: Non-Renewables

6.4.5 Carbon Footprints & Energy Conservation

6.4.6 Case Study: Rice Husks in Bihar

6.4.7 Exam-Style Questions - Energy

6.4.8 Energy - Statistical Skills

Jump to other topics

Unlock your full potential with GoStudent tutoring

Affordable 1:1 tutoring from the comfort of your home

Tutors are matched to your specific learning needs

30+ school subjects covered

Types of Wave

Processes of Erosion & Wave-Cut Platforms

Essay on Weathering and Soil-Forming Factors

Introduction

The breaking down of the earth´s rocks into smaller particles forms the varying sizes of soil, which again constitutes part of the earth’s surface. This process, also known as weathering, occurs due to physical forces and chemical processes leading to the development of the parent material (regolith) for soil formation. Physical weathering alters the size of rock particles, while chemical weathering changes the chemical components of the resulting soil. Chemical agents of weathering include temperature, pressure, and oxygen dissolved in liquid water (Lopez and Macario 457). This experiment involved observing and establishing weathering in the field and then providing detailed field observations to appreciate the natural process. The main research problems entailed weathering observation and then consequent soil formation in the different natural environments and the connection to environmental evidence as interpreted

Materials  Used

• Digital camera

Method /  Procedure

The identification of weathering process involved locating the weathering features. The local geology, landscape, and climate were used in the site identification and study. Three examples of weathering were identified, photos of the weathering features were recorded and the physical location marked. The three identified weathering processes and locations identified in the report are the Canyonlands National Park, Utah, Highway 3, Wainfleet, Ontario, and Lake Nicol, Tuscaloosa, AL. The weathering features identified in the locations were two rock outcrops and an exterior of a building along the highway. Canyonlands National Park, Utah is located in a desert landscape and bound by the colorado river. Lake Nicol, Tuscaloosa, AL is a man-made lake around the city, and therefore the weathering feature may be a result of the exposure to water within the lake hence the mechanical means of disintegration (Anderson 251). Highway 3, Wainfleet, Ontario is a highway within the shores of Lake Erie.

The weathering feature around the location results from exposure to the water from the lake and human activities along the highway. The sizes of the weathering feature varied where the exterior of the building provided the largest size in weathering feature at approximately 20 kilograms of the weathering materials. The other two rock outcrops were at a size approximated at 15 kilograms. Regarding color, the rock outcrops had a brownish color and the exterior of a building had a greyish color. The visible breakdown was identified near all the weathering features. The rock outcrops had coarse-grained particles around them at approximately 70mm in diameter size. The exterior of a building feature o the other hand had medium-grained particles around it approximated at 2mm in diameter size.

Results and Discussion

Three key weathering features were identified and studied, mostly those aspects that were considered as mechanical weathering by-products. Mechanical weathering involves the disintegration of features, including rocks, soil, and minerals into smaller particles as a result of physical/ mechanical agents. Mechanical agents of weathering act as wedges that forces rocks apart and causes the outer layer of rocks to disintegrate (Anderson 248). Highway 3, Wainfleet, Ontario, the Canyonlands National Park, Utah, and the Lake Nicol, Tuscaloosa, AL features weather because they are exposed to nature and especially the waters in the lakes around them. The features are subjected to frost wedging where water from the lakes seeps into the physical features resulting in cracks, especially after the rocks have expanded and freeze, a process typically explained by mechanical weathering involving expansion and wedging ( Anderson 252). The rocks are carried in the lake water over some distance and in this process, these rocks disintegrate. Notably, the resultant size of the end weathering process byproducts of the rock particles depends on the distance the rock particles cover in water. The longer the distance the smaller the particles and the shorter the distance the larger the size of the elements. The Canyonlands National Park, Utah feature can also weather as a result of plant and animal activity around the location.

The presence of animals, as well as plants, otherwise known as biological weathering agents, constitute significantly to the weathering process. Plant roots exert pressure on the rocks around the area, while animals’ movements offer the necessary mechanical pressure to disintegrate these rocks into smaller particles (Lopez and Macario 449). It is worth noting that Highway 3, Wainfleet, Ontario features weather as a result of erosion. The rocks in these regions are exposed to natural forces, such as gravity and other natural forces, leading to their disintegration.

Weathering is the basis of soil formation, and mostly, its agents act solely or collectively in order to foster the weathering process. The extent and rate of weathering depend entirely on the geology, climate, and landscape of a place. Locations exposed to more than a single agent of weathering will experience accelerated weathering, resulting in the formation of fine soil particles. A slow rate of weathering leads to the formation of coarse soil particles which when exposed further to agents of weathering would disintegrate further. This report has experimental results and findings of the weathering and soil formation process, highlighting how various agents contribute to disintegration processes in order to orchestrate different soil characteristics.

Works Cited

Anderson, Suzanne P. “Breaking it Down: Mechanical Processes in the Weathering Engine.”  Elements: An International Magazine of Mineralogy, Geochemistry, and Petrology.  Vol., 15 no. 4, 2019. pp. 247-252.

Lopez, Blanca R., and Macario Bacilio. “Weathering and Soil Formation in Hot, Dry Environments Mediated by Plant–Microbe Interactions.”  Biology and Fertility of Soils . Vol. 56, no.4, 2020. pp 447-459.

Figure.1: Highway 3, Wainfleet, Ontario

Figure.2: Canyonlands National Park, Utah

Figure . .3: Lake Nicol, Tuscaloosa, AL

Cite this page

Similar essay samples.

• A strategic analysis of Eni
• The Camping Tent Case Study
• Mullaly’s Case Study
• In your view, what is the most effective way to address the problem of...
• A discussion of regulatory reform in the OTC derivatives market
• Essay on Balanced Scorecard

• Leaving Cert. Geography (Higher) 2013: Part Two Q3 A-C
• Back to the question >
• Help us make e-xamit better - e-mail support if you spot any errors!
• The content of this site is the intellectual property of e-xamit.ie
• Legal & privacy information

Rocks, Weathering & Mass Movement

Created by studyclix ( 1 ).

Videos from the community ( 0 )

Why not start the community off by adding a post or uploading a resource?

Notes from the community ( 0 )

Websites from the community ( 0 ).

Mechanical and Chemical Weathering essay

Weathering is categorized as mechanical and chemical weathering. The former indicates that temperature and pressure changes cause rocks to disintegrate physically. On the other hand, the latter indicates that the mineral’s structure is altered by either the removal or addition of some elements due to chemical agents (Eastern Illinois University, n. d. ). List and describe the four main types of mechanical weathering and the three main types of chemical weathering discussed in the textbook. Mechanical weathering has four main types: frost wedging, mechanical exfoliation, abrasion, and thermal expansion.

Frost wedging means that water expands when it freezes, thus breaking rocks (Gore, 2004). Mechanical exfoliation means that rocks are exposed to exfoliation when they are exposed to lower confining pressure. Abrasion simply means that rocks rub against each other (Scarborough High School Geoscience, n. d. ). Thermal expansion involves heat and cooling causing the rocks to break (Gore, 2004). Chemical weathering has three types: hydrolysis, dissolution, and oxidation. Hydrolysis indicates the chemical reaction between water and other substances (Scarborough High School Geoscience, n.

d. ). Dissolution refers to the process where rocks are dissolved due to acidic waters (Eastern Illinois University, n. d. ). Oxidation refers to areas that have 21% oxygen in the atmosphere (Scarborough High School Geoscience, n. d. ). Of the three main types of sedimentary rocks (detrital, chemical, and organic), which of those are made-up of components almost entirely (if not entirely) derived from the mechanical weathering of preexisting rocks and/or minerals? Among the main types of sedimentary rocks, the detrital sediment was derived from pre-existing rocks.

The word ‘detrital’ means fragmented or broken grains California State Polytechnic University, n. d. ). One way to lithify sediments is to cement them together. This is typically done via one of three “gluing agents” (silica, calcite, or iron). Which type of weathering (mechanical or chemical) is responsible for the existence of these “gluing agents”? Chemical weathering is responsible for the formation of ‘gluing agents’ such as silicate, calcite, and iron. Lithification itself is a process reflecting chemical weathering. Lithification can occur through the precipitation of silica and calcium or oxidation of aluminum and iron.

Related essays:

• Sedimentary Rocks essay
• Toward people Awareness of Wasting Water in Saudi Arabia essay
• Weathering and Soil essay
• The Effects of Weathering and Erosion essay

Cementation is the process where precipitation of chemical cement from trapped water and circulating water. These ‘gluing agents’ can form as a result of chemical weathering. Silica, calcite, and iron are precipitate types that are chemical in nature (Pidwirny, 2006).

California State Polytechnic University. (n. d. ). Weathering and sedimentary rocks. Retrieved February 11, 2009, from http://geology. csupomona. edu/drjessey/class/Gsc101/Weathering. html Eastern Illinois University. (n. d. ). Mechanical and Chemical Weathering. Retrieved February 11, 2009, from http://www. ux1. eiu.

edu/~cfjps/1300/weathering. html Gore,P. J. W. (2004). Weathering of rocks and formation of sediment. Georgia Perimeter College. Retrieved February 11, 2009, from http://facstaff. gpc. edu/~pgore/geology/historical_lab/weathering. php Pidwirny, M. (2006). Characteristics of sedimentary rocks. Fundamentals of Physical Geography, 2nd Edition. Retrieved February 11, 2009, from http://www. physicalgeography. net/fundamentals/10f. html Scarborough High School Geoscience. (n. d) Weathering. Retrieved February 11, 2009, from http://www. scarborough. k12. me. us/high/projects/geoscience4/sbergg/erosion. htm

Chemical Weathering and Erosion Essay

The video on erosion and weathering basics explains several vital concepts. First of all, it is the difference between weathering and erosion. The speaker uses real-life examples to define what each concept means, which makes it easier to grasp. Weathering means the change in the structure of the ground or material, while erosion is associated with the movement of this material. In addition, the author illustrates the process of chemical weathering by adding vinegar to baking soda. Further, the video elaborates on the agents of weathering and erosion, such as water, wind, gravity, and even ice. Finally, the author talks about different mechanical and physical weathering types, such as abrasions, ice and frost wedging, and exfoliation. Abrasion refers to the collision of Earth material, exfoliation is a process of peeling away rocks in sheets, and ice wedging is weathering caused by the frosting and solidifying of liquids.

The second video on chemical weathering is narrated by the same speaker and focuses on the specific weathering caused by chemical reactions. The first type mentioned is hydrolysis, a material’s response to water. The second essential chemical reaction that causes weathering is oxidation, which happens when the material is exposed to oxygen. This process is also known as rust, which is the name of the reaction between Ferrum and Oxygen. Carbonation is the third type of chemical weathering, and it stands for the reaction of mixing water with carbon dioxide to produce carbonic acid. The lichens such as moss also produce plant acids, which cause alteration of material. Yet, acid precipitation has a much more significant impact on the materials as there is a diverse scope of acids that cause chemical weathering.

• The Processes of Erosion and Deposition
• Erosion and Deposition
• Stages of Erosion
• National Geographic: The 2020 Monsoon
• Geochronology and the Age of Rocks
• A Mineral Appearance and Physical Properties
• Events in the Geomorphic History of the Seal Rocks
• Extinction of Dinosaurs in North America and Texas
• Chicago (A-D)
• Chicago (N-B)

IvyPanda. (2023, May 23). Chemical Weathering and Erosion. https://ivypanda.com/essays/chemical-weathering-and-erosion/

"Chemical Weathering and Erosion." IvyPanda , 23 May 2023, ivypanda.com/essays/chemical-weathering-and-erosion/.

IvyPanda . (2023) 'Chemical Weathering and Erosion'. 23 May.

IvyPanda . 2023. "Chemical Weathering and Erosion." May 23, 2023. https://ivypanda.com/essays/chemical-weathering-and-erosion/.

1. IvyPanda . "Chemical Weathering and Erosion." May 23, 2023. https://ivypanda.com/essays/chemical-weathering-and-erosion/.

Bibliography

IvyPanda . "Chemical Weathering and Erosion." May 23, 2023. https://ivypanda.com/essays/chemical-weathering-and-erosion/.