Glacial and Wave Erosion

Glacial and Wave Erosion

Middle School

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Learning Objectives

• Define and describe the two main types of glaciers and how they form.

• Explain how glaciers shape the land through the processes of erosion and deposition.

• Identify key landforms created by both glaciers and waves.

• Describe how waves erode and deposit sediment to change a coastline.

Key Vocabulary

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Glacier

A large, slow-moving mass of ice formed where more snow falls than melts over many years.

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Continental Glacier

A vast glacier that covers a large island or continent, spreading out and flowing in all directions.

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Valley Glacier

A long, narrow glacier moving downhill through a mountain valley, pulled by the force of gravity.

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Plucking

An erosion process where ice breaks rocks, which then freeze to the bottom of the glacier.

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Abrasion

The process where rock fragments dragged by a glacier or waves wear away the surrounding land.

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Till

A jumbled mixture of different sized sediments that a glacier deposits directly onto the land's surface.

Key Vocabulary

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Longshore Drift

Waves hitting the beach at an angle move sediment along the coast with the current.

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Headland

A part of the shore that sticks out into the ocean, made of hard, resistant rock.

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What Are Glaciers?

• A glacier is a large body of ice that moves slowly on land.

• ​They form when more snow falls than melts, compacting into solid ice.

• Continental glaciers are huge ice sheets covering large areas like Antarctica which move outwards due to weight.

• Valley glaciers are 'rivers of ice' that flow through mountain valleys due to gravity.

Multiple Choice

What are the two main types of glaciers described?

• Continental and Valley

• Mountain and River

• Arctic and Antarctic

• Iceberg and Ice Sheet

Multiple Choice

What is the key difference in how continental and valley glaciers move?

• Continental glaciers flow outward due to their weight, while Valley glaciers flow downhill due to gravity.

• Continental glaciers are found in mountains, while Valley glaciers cover entire continents.

• Continental glaciers are pulled by wind, while Valley glaciers are pulled by ocean currents.

• Continental glaciers are made of saltwater, while Valley glaciers are made of freshwater.

Multiple Choice

If a huge ice sheet covers a large, flat continent like Antarctica, how would it most likely move?

• It would flow outward in all directions because of its immense weight.

• It would flow downhill in a narrow channel like a river.

• It would be pushed in a single direction by the wind.

• It would remain stationary and not move at all.

How Glaciers Shape the Land

• Glaciers erode land by plucking rocks and scraping the ground.

• As glaciers melt, they deposit a sediment mixture called till.

• This creates landforms like moraines, cirques, and U-shaped valleys.

Multiple Choice

What is the main way that glaciers shape the land?

• By eroding the land and depositing sediment

• By freezing rivers and lakes solid

• By melting quickly to cause major floods

• By creating soil for plants to grow

Multiple Choice

How does a glacier's melting lead to the creation of new landforms?

• As a glacier melts, it leaves behind a mixture of sediment called till.

• When a glacier plucks rocks, it sorts them into neat piles.

• When a glacier scrapes the ground, it creates fertile soil.

• As a glacier freezes, it pushes large mounds of ice to the surface.

Multiple Choice

If you were exploring an area that was covered by a glacier thousands of years ago, what evidence would you most likely find?

• A V-shaped valley with a river running through it.

• A flat plain covered in a thick layer of sand.

• A U-shaped valley with piles of till at its base.

• A deep canyon with smooth, vertical rock walls.

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How Waves Shape the Land

• Wind blowing across the water's surface creates most ocean waves.

• Impact is the force of waves hitting the shore, breaking rock.

• Abrasion is when waves use sediment to grind away the land.

• Waves focus their powerful energy on headlands that stick out.

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Multiple Choice

What is the most common way that ocean waves are created?

• Wind blowing across the water's surface

• Earthquakes on the ocean floor

• The gravitational pull of the Moon

• Volcanic eruptions near the coast

Multiple Choice

What is the main difference between how impact and abrasion shape the land?

• Impact is the force of water hitting the shore, while abrasion uses sediment to grind the shore.

• Impact is caused by wind, while abrasion is caused by water.

• Impact breaks down large rocks, while abrasion only smooths small pebbles.

• Impact happens on headlands, while abrasion happens in bays.

Multiple Choice

If a rocky headland sticks out from a coastline, what is the most likely outcome over a long period of time?

• It will be worn down more quickly than the surrounding coastline.

• It will grow larger as waves deposit sand on it.

• It will protect the coastline by stopping all waves.

• It will remain unchanged because it is made of rock.

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Coastal Landforms Created by Waves

Erosional Landforms

• ​Waves can carve out openings in steep, rocky coasts to create sea caves.

• ​​When erosion goes all the way through a headland, it can form a sea arch.

• ​If a sea arch collapses, a tall pillar of rock called a sea stack is left behind.

Depositional Landforms

• ​Waves also deposit sand and other sediment, which creates landforms like a beach.

• ​​The movement of sand along a beach, known as longshore drift, builds up the coastline.

• ​This process can create a spit or a sandbar, which are landforms made of sand.

Multiple Choice

What are the two primary processes by which waves shape coastlines?

• Erosion and deposition

• Freezing and thawing

• Volcanic eruptions and earthquakes

• Wind and rainfall

Multiple Choice

What is the relationship between a sea arch and a sea stack?

• A sea stack is what remains after a sea arch collapses.

• A sea arch is a smaller version of a sea stack.

• Sea stacks are formed by sand, while sea arches are made of rock.

• Sea arches and sea stacks are both created by sand deposition.

Multiple Choice

A coastal area experiences a significant decrease in the amount of sand moving along its beach. What is the most likely long-term effect on this coastline?

• The formation of new spits and sandbars will slow down or stop.

• The coastline will build up much more quickly.

• Sea caves and sea arches will begin to form from the sand.

• The existing beaches will turn into rocky headlands.

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Common Misconceptions

Misconception	Correction
Glaciers are stationary bodies of ice.	Glaciers are constantly in motion, flowing slowly over land.
Wave erosion is always a fast and dramatic process.	Most wave erosion is a very slow, gradual process.
Beaches are permanent and stable landforms.	Beaches are highly dynamic and constantly being reshaped.

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Summary

• Glaciers erode by plucking and abrasion and deposit materials, constantly reshaping land.

• Glaciers create U-shaped valleys, horns, moraines, and kettle lakes.

• Wind-driven waves erode and deposit, continually changing coastlines.

• Wave action forms sea caves, arches, stacks, beaches, spits, and sandbars via longshore drift.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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