Weathering and Soil

Weathering and Soil

Open Ended

While Mari is travelling through Arizona with her family, she sees many interesting rock formations called hoodoos. She takes a photo of one and wonders if it will look the same when they come back to visit again the next year.

Infer what will happen to the hoodoo that Mari saw as time goes by. Explain your answer.

Explanation: The “hoodoo” is a landform that can be worn down by wind, rain, snow, ice, and gravity. Over time, these forces wear rock down and carry it away. Weathering is the process of wearing rocks down. Erosion is the process of wearing rocks down and carrying them away.

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Sample answer: The hoodoo will wear down by weathering and erosion. The forces of wind, rain, snow, ice, and gravity will slowly break the rock apart and carry pieces away. Eventually, the top portion may fall down.

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​Explanation

Multiple Choice

While Mari is travelling through Arizona with her family, she sees many interesting rock formations called hoodoos. A park guide tells her that hoodoos like this one have been forming on Earth throughout history. Which principle explains the process that forms these rocks?

• erosion

• deposition

• weathering

• uniformitarianism

The correct answer is “uniformitarianism.” This principle states that the geologic processes that operate today also operated in the past. Scientists infer that ancient landforms and features formed through the same processes they observe today and will continue to do so in the future. Erosion, weathering, and deposition are all processes that take place during the formation of hoodoos, but they are not a principle.

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​Explanation

Multiple Choice

While Mari is travelling through Arizona with her family, she sees many interesting rock formations called hoodoos. Mari wonders why some parts of the hoodoo seem to be wearing away faster than others. Which factor causes this to happen?

• climate

• type of rock

• temperature

• amount of rainfall

The rate of weathering can differ based on the type of rock. Some softer rocks are worn down faster than the harder rock around them. This is what causes the hoodoo to wear down in some places more than in others. The climate, temperature, and amount of rainfall would affect all types of rock on the hoodoo equally

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​Explanation

Multiple Choice

Ty is looking at some pictures that show examples of different types of weathering. He observes each picture carefully and writes a brief description. Read each of Ty’s descriptions and decide whether the picture shows an example of chemical weathering or mechanical weathering.

A turtle digging a burrow in rocky soil.

• chemical weathering

• mechanical weathering

Multiple Choice

Ty is looking at some pictures that show examples of different types of weathering. He observes each picture carefully and writes a brief description. Read each of Ty’s descriptions and decide whether the picture shows an example of chemical weathering or mechanical weathering.

Lichen is growing on a rock and making it break apart.

• chemical weathering

• mechanical weathering

Multiple Choice

Ty is looking at some pictures that show examples of different types of weathering. He observes each picture carefully and writes a brief description. Read each of Ty’s descriptions and decide whether the picture shows an example of chemical weathering or mechanical weathering.

A rock has become cracked where it has frozen and thawed over and over.

• chemical weathering

• mechanical weathering

Multiple Choice

Ty is looking at some pictures that show examples of different types of weathering. He observes each picture carefully and writes a brief description. Read each of Ty’s descriptions and decide whether the picture shows an example of chemical weathering or mechanical weathering.

An underwater cave is made where water has dissolved the soft limestone rock.

• chemical weathering

• mechanical weathering

​Explanation

​A turtle digging a burrow is an example of mechanical weathering because its actions expose rock to weathering. A rock freezing and thawing will expand and contract causing it to break apart. These are examples of mechanical weathering because the rock is broken down into smaller parts, but does not chemically change. Lichen growing on a rock and breaking it apart is an example of chemical weathering because the rock is being broken down by weak acids in the lichen. The cave formed by water dissolving the soft rock is also an example of chemical weathering because the rock is being dissolved.

Multiple Select

A biologist is examining some soil samples under the microscope. One sample was obtained from some woods nearby and the other sample was from a nearby beach. Which of these would she expect to see in the soil from the beach that would not be in the soil from the woods? Choose the two that apply.

• sand particles

• clay

• humus

• shell pieces

​Explanation

​Soil is made from broken-down weathered materials. The soil from a beach would most likely contain sand particles and broken-down pieces of shell. Clay and humus are not likely to be found in the soil at the beach. These materials would be more likely found in the soil in the forest.

Multiple Choice

A gardener is adding topsoil to his garden to help keep his flowers healthy. As he pours the bags of soil, he wonders about the processes which caused the soil to be made. What happens first?

• Topsoil is formed.

• Dead leaves fall onto the ground.

• Bedrock is weathered into small pieces.

• Leaves and dead roots decay and are broken down.

• Organisms such as earthworms mix decaying matter with sediment.

Multiple Choice

A gardener is adding topsoil to his garden to help keep his flowers healthy. As he pours the bags of soil, he wonders about the processes which caused the soil to be made. What happens second?

• Topsoil is formed.

• Dead leaves fall onto the ground.

• Bedrock is weathered into small pieces.

• Leaves and dead roots decay and are broken down.

• Organisms such as earthworms mix decaying matter with sediment.

Multiple Choice

A gardener is adding topsoil to his garden to help keep his flowers healthy. As he pours the bags of soil, he wonders about the processes which caused the soil to be made. What happens third?

• Topsoil is formed.

• Dead leaves fall onto the ground.

• Bedrock is weathered into small pieces.

• Leaves and dead roots decay and are broken down.

• Organisms such as earthworms mix decaying matter with sediment.

Multiple Choice

A gardener is adding topsoil to his garden to help keep his flowers healthy. As he pours the bags of soil, he wonders about the processes which caused the soil to be made. What happens fourth?

• Topsoil is formed.

• Dead leaves fall onto the ground.

• Bedrock is weathered into small pieces.

• Leaves and dead roots decay and are broken down.

• Organisms such as earthworms mix decaying matter with sediment.

Multiple Choice

A gardener is adding topsoil to his garden to help keep his flowers healthy. As he pours the bags of soil, he wonders about the processes which caused the soil to be made. What happens last?

• Topsoil is formed.

• Dead leaves fall onto the ground.

• Bedrock is weathered into small pieces.

• Leaves and dead roots decay and are broken down.

• Organisms such as earthworms mix decaying matter with sediment.

​Explanation

The process of soil formation begins with bedrock breaking down by the process of weathering. Next, leaves fall onto the ground. The leaves and other dead matter begin to decay. Organisms, such as worms, mix the decaying matter in with the sediment. This eventually results in the formation of topsoil.