Earth's Changing Surface

Earth's Changing Surface

Middle School

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Learning Objectives

• Define and differentiate between weathering, erosion, and deposition.

• Distinguish between gradual and catastrophic changes to Earth's surface.

• Identify landforms created by different types of erosion.

• Explain how natural processes and human activities can affect the rate of erosion.

Key Vocabulary

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Weathering

The natural process of breaking down rocks and soil into smaller particles over a long period.

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Erosion

The process of transporting weathered rocks and soil from one place to another by natural forces.

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Deposition

The natural process where eroded sediment is dropped and builds up in a new location.

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Gradual Change

A slow process that alters Earth's surface over thousands or millions of years, like mountain formation.

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Catastrophic Change

A sudden, dramatic event that rapidly changes the Earth's surface, such as a large asteroid impact.

Weathering, Erosion, and Deposition

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Weathering

• This is the destructive process that breaks down rock or soil.

• Forces like wind, water, and ice can slowly break rocks apart.

• Plant roots and temperature changes also contribute to breaking down rocks.

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Erosion

• This destructive process transports weathered materials from one place to another.

• Natural forces like gravity, wind, and water carry loose material away.

• Human activities, like removing plants from a field, can increase erosion.

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Deposition

• This is the constructive process where eroded sediment is dropped or settles.

• It happens when the transporting force, like wind or water, slows down.

• Deposition creates new landforms, such as deltas and beautiful sand dunes.

Multiple Choice

Which statement correctly identifies the roles of weathering, erosion, and deposition?

• Weathering drops materials, erosion breaks them down, and deposition moves them to a new place.

• Weathering breaks down rock, erosion moves the pieces, and deposition drops them in a new place.

• Weathering moves materials, erosion breaks them down, and deposition drops them in a new place.

• Weathering breaks down rock, erosion drops the pieces, and deposition moves them to a new place.

Multiple Choice

What is the primary cause of deposition?

• Human activities, like clearing a field of plants, expose loose soil.

• Gravity pulls loose material from one place to another.

• The force carrying sediment, like wind or water, slows down.

• Plant roots grow into cracks in rocks, breaking them apart.

Multiple Choice

Over millions of years, a river carves a deep canyon and then forms a large, fan-shaped delta where it meets the ocean. Which statement best explains this sequence?

• Deposition created the canyon, and weathering formed the delta.

• Deposition was the main process that carved the canyon.

• Erosion was the main process that formed the delta.

• Weathering and erosion carved the canyon, while deposition formed the delta.

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Gradual vs. Catastrophic Changes

Gradual Changes

• These changes occur slowly over thousands or even millions of years, gradually altering the landscape.

• Processes like erosion by water or wind wear away landforms over vast periods of time.

• Mountain formation from the slow collision of tectonic plates is another example of gradual change.

Catastrophic Changes

• These events happen very quickly and dramatically, often in just moments, days, or months.

• They cause sudden and major transformations to the Earth's surface and environment.

• Examples include volcanic eruptions, earthquakes, floods, hurricanes, and large asteroid impacts.

Multiple Choice

What is the primary difference between gradual and catastrophic changes to the Earth's surface?

• The type of animals affected by the change

• The location where the change takes place

• The time frame over which the change happens

• The season in which the change occurs

Multiple Choice

Which of the following describes the relationship between tectonic plate collisions and mountain formation?

• Mountains are formed catastrophically by sudden plate collisions.

• Tectonic plates only cause catastrophic events like earthquakes, not mountain formation.

• Mountain formation is a rapid process, while plate collisions are slow.

• Mountains are formed gradually by the slow collision of plates over time.

Multiple Choice

A coastal area is struck by a major hurricane, causing widespread flooding and reshaping the shoreline in just a few days. Which statement best explains why this is considered a catastrophic event?

• Because it caused a major transformation very quickly.

• Because it happened near the ocean.

• Because it was a natural process.

• Because it will slowly change the landscape over millions of years.

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Types of Erosion

Coastal Erosion

• The power of waves and currents wears away rocks on the shore.

• This process carves out landforms like sea caves, arches, and stacks.

• The constant action of water reshapes the edge of the land.

Glacial Erosion

• Large masses of ice called glaciers scrape and smooth the land.

• As they move forward, they carve out the ground beneath them.

• When the glaciers melt, they can form new rivers and lakes.

Multiple Choice

What is the primary way that erosion affects land?

• It builds up new layers of soil.

• It helps new types of plants grow.

• It wears away, carves, or reshapes the land.

• It causes glaciers and ice to form.

Multiple Choice

What is the key difference between coastal erosion and glacial erosion?

• Coastal erosion happens quickly, while glacial erosion happens slowly.

• Coastal erosion is caused by waves and currents, while glacial erosion is caused by large masses of ice.

• Coastal erosion is caused by moving ice, while glacial erosion is caused by moving water.

• Coastal erosion creates lakes, while glacial erosion creates sea caves.

Multiple Choice

A large glacier carves a deep valley over thousands of years. Based on the information provided, what is a likely outcome after this glacier melts?

• The valley will be filled in by the action of waves and currents.

• Sea caves and arches will begin to form in the valley.

• The land will quickly return to its original, flat shape.

• A new river or lake may form in the space the glacier carved out.

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Modeling Erosion

• Scientists use models like stream tables to study how erosion shapes the land.

• ​They change one factor at a time, a variable, to observe its effects.

• Key variables include the table’s tilt and the amount of water flow.

• Other variables are the amount of vegetation and the type of soil used.

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Multiple Choice

What is the main purpose of using a model like a stream table in science?

• To demonstrate how to build a real river

• To provide a habitat for small aquatic animals

• To create a decorative water feature for a classroom

• To study how the process of erosion shapes the land

Multiple Choice

When using a stream table, why would a scientist choose to change only the amount of water flow in an experiment?

• To make the experiment last longer

• To test how well different types of soil absorb water

• To isolate and observe the specific effect of water flow on erosion

• To see how multiple changes affect the outcome at once

Multiple Choice

A scientist is modeling erosion and wants to investigate how plants can help protect a hillside. Which experimental setup would best test this idea?

• Comparing two tables with different tilts but the same vegetation

• Comparing two tables with different amounts of water flow but the same tilt

• Comparing two tables with different types of soil but the same water flow

• Comparing two tables with and without vegetation, but with the same soil, tilt, and water flow

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Common Misconceptions

Misconception	Correction
Weathering and erosion are the same thing.	Weathering breaks down rock, while erosion moves the pieces to a new location.
All changes to Earth's surface happen very slowly.	Sudden events like floods and volcanoes can change the surface very quickly.
Erosion is only a destructive process.	Erosion is linked to deposition, a constructive process that builds new landforms.

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Summary

• Earth's surface is shaped by gradual processes and catastrophic events.

• Weathering breaks down rock, erosion moves it, and deposition builds new land.

• Water, ice, wind, and human activities are powerful forces of erosion.

• Scientists use models to understand the variables that affect erosion.

Poll

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