Weathering of rocks and soil formation
Earth Science - Middle School
Earth's Surface
Multimedia Lesson
Rocks
Multimedia Lesson
Weathering and Erosion Overview
Presentation
The Erosion and Deposition Cycle
Presentation
Mechanical and Chemical Weathering
Presentation
Forces of Erosion and Deposition
Presentation
Soil
Presentation
The Rock Cycle
Presentation
Rock Cycle
Interactive
Weathering of rocks and soil formation
Study Guide
Weathering of rocks and soil formation
Quiz
Weathering of rocks and soil formation
Flash Cards
Weathering of rocks and soil formation
Worksheet
Weathering of rocks and soil formation
Game
Weathering of rocks and soil formation
Vocabulary List
Weathering of Rocks & Soil Formation
Flip Chart
Weathering and Erosion
Flip Chart
Erosion and Deposition Cycle
Flip Chart
Mechanical Weathering
Flip Chart
Chemical Weathering
Flip Chart
Soil
Flip Chart
Earth’s Surface Vocabulary Review
Flip Chart
Study Guide Weathering of rocks and soil formation
❮
1
/
5
❯
WEATHERING OF ROCKS AND SOIL Weathering is a collection of natural processes that, over time, break large rock into smaller and smaller pieces. Rocks can be decomposed, that is, broken down, by physical processes (called mechanical weathering) and chemical processes (called chemical weathering). When a piece of rock of any size moves during weathering, the process is then called erosion. When the force of gravity pulling material downhill causes erosion, it is called mass wasting. Mechanical Weathering Mechanical weathering is the physical decomposition of rocks. There are a number of physical processes that break rock down into smaller and smaller pieces. 1. Mechanical weathering can happen by the abrasion of one rock banging against another. 2. When the sun heats rocks during the day, they expand. When they cool at night they contract. This repeated expanding and contracting can cause some rocks to flake apart at the surface which is called exfoliation. 3. Small cracks can fill with water. When the water freezes it expands which pushes the rock apart, splitting it. Repetitive cycles of freezing and thawing pushes the pieces of rock further apart from each other. This process is called frost wedging. 4. Cracks in rocks fill with dust and dirt. Trees and plants take root in this dirt and as the trees grow, the roots grow. Expanding roots actually can have enough force to push rocks apart. Running water rolls rock pieces against each other, breaking the rocks down and polishing their edges. 5. Glaciers break rocks apart and crush rocks against each other as they move from higher to lower elevations. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
6. Ocean waves pound against coastal rocks. The force of the waves themselves slowly breaks down the rock formations. The waves also push smaller pieces of rock and other debris against larger rocks, grinding both into smaller pieces. 7. Wind blows small particles against rocks which slowly sands the rocks down, much like sandpaper sands wood. Lesson Checkpoint: Name two ways that mechanical weathering wears down rock. Chemical Weathering Chemical weathering is the decomposition of rocks by chemical reactions. The chemicals can be from natural sources, such as the decomposition of sulfide minerals like pyrite. In modern times, the chemicals can also be the byproduct of pollution created by the burning of fossil fuels. Here is a list of some forms of chemical weathering. 1. Limestone is dissolved by acid rain. Sulfur is released into the atmosphere when fossil fuels are burned. The sulfur combines with water to form sulfuric acid. These acids slowly dissolve some types of rock. 2. Sulfur released by the decomposition of sulfide minerals like pyrite can also combine with water making the water acidic. This acidic water can then react with certain rocks to break them down. This is called pyrite decay and is a particular problem near the waste piles of old mines. 3. Natural carbonic acid in water eats through limestone to create extensive limestone caves and cave formations such as stalactites and stalagmites. 4. Some lichen and tree roots produce acid in their tips. The acid is used to eat through rock so that the plant can anchor itself to a substrate and also find nutrition. This acid is strong enough to decompose rock. 5. Many minerals are relatively unstable and easily deteriorate in the presence of water and natural chemicals. Feldspar in granite, for example, breaks down into clay. Lesson Checkpoint: Describe one type of chemical weathering. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
How Does Soil Form? Soil is a combination of decomposed rock and organic materials. There are different types of soil depending on the climate in which they form. Geologists study soil by studying the soil profile. The soil profile is a cross-section of the soil from the surface down to the hard bedrock (also called parent rock). The soil profile is subdivided into horizons. The uppermost is the A horizon and consists primarily of decaying organic material. (Sometimes the A horizon is broken into the O horizon on top of the A horizon below.) This material is called humus. The B horizon is also called the subsoil. The C horizon contains partially decomposed bedrock or parent rock material. Below the C horizon is unaltered parent rock. Soil that is formed over its parent bedrock is called residual soil. Soil that has been transported from a different location and then deposited is called transported soil. All soil begins with the underlying parent rock. Mechanical and chemical processes weather this parent rock. As the rock deteriorates, biological material is mixed with the rock pieces. The biological material is usually mostly plant material, but it can also be animal remains as well. As water percolates down through the soil horizon, it leaches nutrients and minerals from the surface and moves them downward into the lower soil horizons. The C horizon, however, is generally devoid of nutrients. Lesson Checkpoint: Which layer of soil has no nutrients? © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Types of Soil The physical characteristics of the soil that forms in any particular region is determined by the region’s climate. 1. Tropical regions have dense vegetation and high rainfall. The topsoil in tropical regions is very thin because the high rainfall constantly and quickly leaches the topsoil. 2. Desert climates have very low rainfall. The little rain that does fall generally evaporates quickly. Soluble minerals that are dissolved in the rainwater are then easily left behind. This is a harsh environment for plants to survive, so there is very little vegetation. Desert soil, therefore, has little to no humus and cannot support much plant life. 3. Temperate climates have the most nutrient-rich, productive soils in the world. They have a thick humus layer. They get enough rain to nourish the plant life, but not so much that the soil is leached of its nutrients. The soil horizon, therefore, has a very thick A horizon. 4. Arctic climates have very little rain, just like the hot desert climates. There is very little chemical weathering. There is also very slow soil formation. Arctic soil is very thin and cannot support much plant life. Lesson Checkpoint: Which type of climate has the most productive soil? Life in the Soil Different soils can support different types of life. Soils with rich A horizons (that is, with a lot of humus) are able to support abundant plant life, as well as fungi, bacteria, insects, worms and a variety of small and medium-sized animals. Fungi and bacteria decompose plant material. Worms and insects also break down the decomposing plant material. Animals make their homes in the soil where they live, breed and find protection from predators. Burrowing animals also help create the soil profile by breaking up lower horizons and helping break down hard dirt, soil and rock. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Soil conservation Soil is essentially a nonrenewable resource. Without careful use, it can be easily and quickly depleted and even destroyed. For example, in the 1920’s, farmers in states like Kansas were devastated by a series of events that resulted in the topsoil literally being blown away by the wind in tremendous clouds of dust. Historians call this “The Great Dustbowl.” This problem was created by the widespread removal of the grasses that grew on the topsoil (called cover crops) which allowed considerable erosion. The dramatic removal of cover crops, like grasses and wildflowers, will lead to rapid erosion of the topsoil. Since the topsoil holds considerable quantities of water, loss of this natural “sponge” can lead to dramatic flooding. Similarly, water management can become a problem when an area is overdeveloped with homes, businesses, parking lots and roads. When the soil is removed or covered, the water that would have been held by the soil now must run off somewhere. Soil conservation is also an important consideration for farmers. For example, if a crop is planted on the same soil year after year, certain nutrients will eventually be completely depleted from that soil. Consequently, farmers rotate crops to replenish these nutrients and keep the soil productive for many seasons. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Table Of Contents: Earth's Surface
1. Weathering and Erosion Overview
2.1. Weathering and Erosion
Forces of weathering and erosion are constantly reshaping the Earth’s surface. Weathering is a group of natural processes that break rock into smaller pieces over time. Erosion occurs when rock and soil are transported.
2.2. Mechanical and Chemical Weathering
The two types of weathering are mechanical and chemical. Mechanical weathering is the physical decomposition of rocks. Chemical weathering is the decomposition of rocks by chemical reactions.
2.3. How Is Rock Eroded?
Rock can be eroded by many forces such as blowing wind, running water, ocean waves, flowing ice and gravity. These forces all contribute to sculpting the Earth’s landscape.
2. The Erosion and Deposition Cycle
3.1. Steps of the Erosion and Deposition Cycle
The cycle of erosion and deposition has many steps. First, weathering breaks down rock, and then erosion transports the material. Deposition occurs and sediments begin to accumulate. Over time these sediment layers lithify and become stone.
3.2. Sediment Deposited in the Ocean
Sometimes the erosion and deposition cycle is repeated. Sediment eventually makes it way from the high points of continents, down through rivers, and into oceans.
3. Mechanical and Chemical Weathering
4.1. Abrasion and Plant Growth
There are many examples of mechanical weathering. Abrasion occurs when one rock grinds against another. A rock can also break when plant roots grow into cracks on its surface.
4.2. Exfoliation and Frost Wedging
Exfoliation is a repeated cycle during which rocks expand in the daytime heat and contract at night, causing rocks to flake. Frost wedging occurs when cracks fill with water and undergo a repeated cycle of freezing and thawing, causing rocks to crack apart.
4.3. What is Chemical Weathering?
Chemical weathering involves the breaking down of rocks by chemical reactions. The three main chemical reactions that decompose rocks are acid reactions, oxidation and hydrolysis.
4.4. Natural Chemical Weathering
Acid-producing lichen and tree roots that eat through rock are natural sources of chemical weathering. Many minerals are also relatively unstable and deteriorate in the presence of water and natural chemicals. For example, the feldspar found in granite breaks down into clay.
4.5. Chemical Weathering and Pollution
Chemical weathering can be caused by pollution. Acid rain, created by the burning of fossil fuels, dissolves some types of rocks such as limestone.
4. Forces of Erosion and Deposition
5.1. Natural Forces of Erosion and Deposition
Many natural forces cause erosion and deposition, including gravity, moving water, glaciers, ocean waves and wind. These forces continuously wear down and build up material on the Earth’s surface.
5.2. Gravity and Mass Movements of Rock
Gravity can cause unstable rock material to move suddenly. Landslides and mudflows occur when loose soil and rocks slide down steep slopes. Slump is the sudden movement of a single large mass of rock material. Creep is caused by gravity, but is a slow downhill movement of sediment over time.
5.3. Moving Water Carries Sediment
Rivers and streams move across the Earth's surface and shape the landscape. Flowing water has enough energy to move large amounts of sediment, composed of soil, rock, clay and sand. The amount of sediment that is carried by a river or stream is called its load.
5.4. Deltas and Alluvial Fans
When a river empties into an ocean or lake, sediments are deposited and a triangular-shaped delta is formed. When water transports sediments from a hilly area to a flat area, the water slows down and sediment forms an alluvial fan.
5.5. Glaciers Shape the Land
Glaciers are massive sheets of ice that form over continents and in high altitude mountains.Glaciers move and shape the land by grinding, breaking and transporting rocks. Continental glaciers create flat landscapes while alpine glaciers create rugged, mountain features.
5.6. Glacier Landforms
Glacial erosion creates many landforms including mountain horns, cirques, aretes and U-shaped valleys. When a glacier melts, the deposited sediment left behind is called glacial drift. Moraines, drumlins and kettle lakes are landforms created by glacial drift.
5.7. Waves and Rock Formations
Ocean waves contain energy that breaks down rock and shapes coastlines. Rock formations created by wave erosion include headland cliffs, sea caves, sea arches and sea stacks.
5.8. Waves and Deposition
Waves also move and deposit rocks, sediment and sand. Beaches are composed of different sources of eroded rock. Barrier spits are created from longshore wave currents, and sandbars are built up offshore by incoming storm waves.
5.9. Wind Erosion and Deposition
Wind causes erosion through deflation, the blowing away of surface materials, and through abrasion, the grinding down of rock by blown particles. Wind also deposits sand into land formations such as sand dunes and loess deposits.
5. Pause and Interact
6.1. Review
Use the whiteboard tools to complete the activity.
6.2. Forces of Erosion and Deposition
Follow the onscreen instructions.
6. Soil
7.1. What Is Soil?
Soil is a combination of broken down rock and decomposed organic materials. Geologists study the soil profile, which is a cross section of the soil from the surface down to the bedrock. The soil profile is divided into layers called horizons.
7.2. Types of Soil
Soil is classified according to climate, plant vegetation and soil composition. Different types of soil are found in different climate biomes. Plant vegetation impacts the amount of organic material called humus that is found in the topsoil.
7.3. Climates with Thin Soil Layers
Tropical climates with lush vegetation often have a thin layer of topsoil because high rainfall washes away humus and minerals in the A horizon. Soil layers are also thin in harsh climates such as deserts and arctic regions.
7.4. Soil in Temperate Climates
Temperate climates have the most nutrient-rich, productive soils. Moderate rainfall results in abundant plant life, and the soil profile has a thick layer of topsoil with humus.
7.5. Life in the Soil
Many organisms live in the soil and contribute to its formation. Burrowing animals help create the soil profile by breaking up rock and other materials. Worms, fungi and bacteria decompose decaying matter.
7.6. Soil Conservation
Soil is a non-renewable resource that can be easily depleted or destroyed. Removal of cover crops like grasses and wildflowers leads to rapid soil erosion. Without cover plants, wind can blow away topsoil in clouds of dust, and significant flooding can occur.
7.7. Topsoil and Farming
Many modern farmers use techniques to conserve soil. Crop rotation prevents depletion of soil nutrients. Low-till plowing minimizes soil disturbance, and contour plowing reduces the erosion of topsoil from water runoff.
7. Pause and Interact
8.1. Review
Use the whiteboard tools to complete the activity.
8.2. Soil Profile
Click on the Terms button. Then click and drag each term to the correct box. Use the reset button to clear the terms and start over. Use the gear button to customize the draggable terms.
8. Landforms and Topographic Maps
9.1. Types of Landforms
Three major types of landforms are plains, plateaus and mountains. A plain is a large region of nearly flat or gently rolling land with little change in elevation. A plateau is a highly elevated flat region that often contains rivers and streams. Mountains are high elevation landforms with steep slopes.
9.2. What Is a Topographic Map?
A topographic map provides information about the surface features of a particular area. Topographic maps show natural features such as rivers and mountains as well as human-made features like buildings, roads and bridges. The symbols that represent map features are found in the legend.
9.3. Topographic Map Contour Lines
Contour lines on a topographic map connect points of equal elevation. An index contour is a darker, heavier line with a marked elevation. The contour interval is the difference in elevation between two contour lines. The relief is the vertical distance between the highest and lowest elevation points on the map.
9.4. Topographic Map Rules
There are some basic rules to remember when reading a topographic map. Contour lines never cross. When contour lines are spaced close together, the slope is steep. If they are spread apart, the slope is gentle. Contour lines that cross a valley or stream are V-shaped with the V pointing toward the higher elevation. Tops of hills or depressions are shown as closed circles.
9. Vocabulary Review
10.1. Earth's Surface Vocabulary Matching
In this virtual investigation you will practice reading topographic maps and making topographic profiles. Topographic maps represent a view of the landscape from above. You can use the information from a topographic map to create a cross-section view of a particular region of the map called a profile. A profile can help you better understand the details of a landform such as a mountain.
10. Virtual Investigation
11.1. Topographic Maps
In this virtual investigation you will practice reading topographic maps and making topographic profiles. Topographic maps represent a view of the landscape from above. You can use the information from a topographic map to create a cross-section view of a particular region of the map called a profile. A profile can help you better understand the details of a landform such as a mountain.
11. Assessment
12.1. Earth's Surface
NewPath Learning
About Us Our Team Awards & Endorsements Grants & Funding Product Suggestions Custom Publishing Collaborate Online Our BlogSolutions
Review & Reinforcement Intervention & Enrichment Test Prep After School/Summer School Parental Involvement Professional DevelopmentShop By Product
Curriculum Mastery Games Flip Charts Visual Learning Guides Curriculum Learning Modules E-Books/Workbooks Posters & Charts Study/Vocabulary Cards Digital Curriculum Online Learning Online Printable WorksheetsShop By Grade
Early Childhood First Grade Second Grade Third Grade Fourth Grade Fifth Grade Sixth Grade Seventh Grade Eighth Grade High School
© 2025 NewPath Learning all right reserved | Privacy Statements | Term of use | Website design WinMix Soft
