Chapter 2: Landforms Chapter 2: Landforms of Georgia of Georgia

Lesson 2: What Causes Changes To Lesson 2: What Causes Changes To Landforms?Landforms?

S5E1a: Student will identify features S5E1a: Student will identify features caused by constructive processes.caused by constructive processes.

S5E1b: Student will identify and find S5E1b: Student will identify and find examples of surface features caused by examples of surface features caused by

destructive processes. destructive processes.

Vocabulary PreviewVocabulary Preview

Weathering: the process of wearing away Weathering: the process of wearing away rocks by natural meansrocks by natural means

Erosion: the process of moving sediment Erosion: the process of moving sediment by wind, moving water, or iceby wind, moving water, or ice

Delta: an area of new land at the mouth of Delta: an area of new land at the mouth of a river, formed from sediments carried by a river, formed from sediments carried by the riverthe river

Sinkhole: a large hole formed when the Sinkhole: a large hole formed when the roof of a cave collapsesroof of a cave collapses

Changes Caused By Wind Imagine yourself standing Imagine yourself standing

on a beach with your face on a beach with your face to the wind. to the wind.

Sand hits your face so hard Sand hits your face so hard that is begins to sting. that is begins to sting.

Now imagine this blowing sand hitting a rock.

Over time, the sand wears Over time, the sand wears away the rock by breaking away the rock by breaking it into smaller pieces. it into smaller pieces.

The process of wearing The process of wearing away rocks by natural away rocks by natural means is known as means is known as weathering. .

Changes Caused By WindChanges Caused By Wind The weathered pieces of rock, some as large as The weathered pieces of rock, some as large as

sand grains, are carried away by the wind. sand grains, are carried away by the wind. The pieces keep moving as long as the wind is The pieces keep moving as long as the wind is

blowing. blowing. But when the wind slows down, the large pieces But when the wind slows down, the large pieces

fall to the ground. fall to the ground. Over a long time, the wind leaves small piles of Over a long time, the wind leaves small piles of

sand in an area. sand in an area. These piles grow as more sand is blown into the These piles grow as more sand is blown into the

pile. pile. Slowly, they become sand dunes. Slowly, they become sand dunes.

A mushroom rock like all of these, have this shape because the wind blew sand around the bottom of the rock, wearing it away.

Changes Caused By WindChanges Caused By Wind Sand dunes are found in many places such Sand dunes are found in many places such

as in deserts, at beaches, and on as in deserts, at beaches, and on lakeshores. lakeshores.

Some deserts dunes are as high as a 30-Some deserts dunes are as high as a 30-story building!story building!Many beaches along the Atlantic Coast Many beaches along the Atlantic Coast have long lines of dunes. have long lines of dunes.

These dunes help protect the land during These dunes help protect the land during storms. storms.

But they can also damage nearby building But they can also damage nearby building and roads as the move inland, pushed by and roads as the move inland, pushed by winds from the ocean.winds from the ocean.

Changes Caused by Moving WaterChanges Caused by Moving Water

Suppose your hands are Suppose your hands are dirty after working in the dirty after working in the gardengarden

Rinsing your hands Rinsing your hands removes most of the soil. removes most of the soil.

The water flows over your The water flows over your hands, picks up the soil, hands, picks up the soil, and carries it away. and carries it away.

In a similar way, moving In a similar way, moving water can change Earth’s water can change Earth’s surface by carrying soil surface by carrying soil and small pieces of rock and small pieces of rock away from landforms. away from landforms.

Changes Caused by Moving WaterChanges Caused by Moving Water

The process of moving sediment by wind, The process of moving sediment by wind, water, or ice is called water, or ice is called erosionerosion. .

Water is an important cause of change for Water is an important cause of change for Earth’s landforms. Earth’s landforms.

Moving water can dig a mile-deep canyon Moving water can dig a mile-deep canyon or change the path of a river. or change the path of a river.

Ex: A rapidly flowing river erodes its banks Ex: A rapidly flowing river erodes its banks and its bottom. and its bottom.

Eroding the banks makes the river wider Eroding the banks makes the river wider and eroding the bottom makes the river and eroding the bottom makes the river deeper. deeper.

These canyons are examples of changes made by moving water. For millions of years, the river has been wearing away rocks and carrying sediment downstream. The river has carved deeper and deeper into the landforms.

Changes Caused by Moving WaterChanges Caused by Moving Water

The moving water then carries The moving water then carries sediment downstream. sediment downstream.

When the flow of water slows down, When the flow of water slows down, sediment is deposited. sediment is deposited.

Deposits on a river’s banks make it Deposits on a river’s banks make it narrower. narrower.

Deposits on the bottom make the Deposits on the bottom make the river shallower. river shallower.

Erosion and DepositionErosion and Deposition

Moving wind or water has energy, which Moving wind or water has energy, which enable it to move sediment. enable it to move sediment.

The faster the wind or water moves, the The faster the wind or water moves, the more energy it has. more energy it has.

Fast water, with a lot of energy, can erode Fast water, with a lot of energy, can erode a lot of sediment. a lot of sediment.

Slow water, with litter energy, can erode Slow water, with litter energy, can erode only a small amount of sediment. only a small amount of sediment.

But all moving water, even a gentle rain, But all moving water, even a gentle rain, can erode some sediment. can erode some sediment.

Crashing waves can change the face of a cliff.

Erosion and DepositionErosion and Deposition

Rain doesn’t seem very powerful, but it Rain doesn’t seem very powerful, but it can still cause erosion. can still cause erosion.

When rain falls on a bare hill or mountain, When rain falls on a bare hill or mountain, it splashes away soil. it splashes away soil.

As it runs downhill, the water increases its As it runs downhill, the water increases its speed and gains energy. speed and gains energy.

The moving water carries away sediment. The moving water carries away sediment. Over time, water erosion may leave Over time, water erosion may leave

gullies, or ditches in the ground. gullies, or ditches in the ground.

Erosion and DepositionErosion and Deposition Ocean waves also cause erosion. Ocean waves also cause erosion. Constant wave action can cause changing sloping Constant wave action can cause changing sloping

shorelines into cliffs. shorelines into cliffs. Waves crashing against the shore carry away Waves crashing against the shore carry away

broken bits of rock. broken bits of rock. Piece by piece, the cliffs get steeper.Piece by piece, the cliffs get steeper. In many places, there is so much erosion that the In many places, there is so much erosion that the

top of a cliff overhangs the bottom. top of a cliff overhangs the bottom. When this happens, the entire cliff can collapse When this happens, the entire cliff can collapse

into the ocean. into the ocean. Then waves begin eroding the collapsed rock and Then waves begin eroding the collapsed rock and

form new cliffs. form new cliffs.

Erosion and DepositionErosion and Deposition Ocean waves change landforms in another Ocean waves change landforms in another

way, too. way, too. If you stand on a beach and watch the If you stand on a beach and watch the

waves, you see that each wave brings waves, you see that each wave brings more sand onto the beach. more sand onto the beach.

The process by which sediment is carried The process by which sediment is carried in water as long as the water flows fast. in water as long as the water flows fast.

Fast-flowing water has a lot of energy. Fast-flowing water has a lot of energy. When water slows down, it loses energy. When water slows down, it loses energy. Larger pieces of sediment drop out of the Larger pieces of sediment drop out of the

water first and settle to the bottom. water first and settle to the bottom.

Floods deposit nutrient-rich soil on the flood plain.

When the Mississippi River enters the Gulf of Mexico, the water slows down. Sediment is deposited, and the delta grows.

Erosion and DepositionErosion and Deposition As the water slows down more, smaller As the water slows down more, smaller

and smaller particles sink to the bottom. and smaller particles sink to the bottom. A river often deposits sediment at its A river often deposits sediment at its

mouth, the place where it empties into the mouth, the place where it empties into the ocean. ocean.

The flow of water slows as a river reaches The flow of water slows as a river reaches the ocean. the ocean.

As a result, much of the sediment the river As a result, much of the sediment the river carries is deposited, forming a delta. carries is deposited, forming a delta.

A A deltadelta is an area of new land at the is an area of new land at the mouth of a river. mouth of a river.

Delta Pictures: A area of new land formed at the mouth of a river.

Erosion and DepositionErosion and Deposition Flooding can deposit sediment near a Flooding can deposit sediment near a

river. river. During heavy rains, a flooding river sends During heavy rains, a flooding river sends

water over its banks. water over its banks. When the rains end, the water slowly When the rains end, the water slowly

returns to the river, but the sediment it returns to the river, but the sediment it carried is deposited on the land. carried is deposited on the land.

This sediment is rich in nutrients that This sediment is rich in nutrients that plants need. plants need.

As a result, flood plains, as these areas are As a result, flood plains, as these areas are called, are usually good for farming. called, are usually good for farming.

Sinkholes and LandslidesSinkholes and Landslides Water can change not only landforms on Earth’s Water can change not only landforms on Earth’s

surface but also features underground.surface but also features underground. Ex: Groundwater can weather and erode soft Ex: Groundwater can weather and erode soft

rocks.rocks. Underground erosion causes caves to form. Underground erosion causes caves to form. Often the roof of a cave collapses due to the Often the roof of a cave collapses due to the

weight of material above it. weight of material above it. If the cave is near the surface, a large hole, called If the cave is near the surface, a large hole, called

a a sinkholesinkhole, may suddenly open. , may suddenly open. Most sinkholes are found where limestone is Most sinkholes are found where limestone is

common, such as Florida. common, such as Florida.

Sinkholes

Sinkholes and LandslidesSinkholes and Landslides

Water isn’t the only factor that cause Water isn’t the only factor that cause erosion and deposition. erosion and deposition.

Gravity can also cause these land-Gravity can also cause these land-changing process to happen. changing process to happen.

Gravity can make soil, mud, and rocks Gravity can make soil, mud, and rocks move quickly down a slope. move quickly down a slope.

This form of erosion is called a landslide. This form of erosion is called a landslide. Landslides can happen suddenly, Landslides can happen suddenly,

especially after heavy rains or especially after heavy rains or earthquakes.earthquakes.

Landslides

PlantsPlants Plants can also cause Plants can also cause

weathering and weathering and erosion. erosion.

When a seed When a seed germinates on a rocky germinates on a rocky slope, it sends roots slope, it sends roots into tiny cracks or into tiny cracks or holes in the rock. holes in the rock.

The roots grow and The roots grow and may eventually may eventually become large enough become large enough to break the rock into to break the rock into smaller pieces. smaller pieces.

The growth of plant roots can weather rock.

PlantsPlants Plants don’t just weather Plants don’t just weather

rock. rock. They also preserve and They also preserve and

protect Earth’s landforms. protect Earth’s landforms. Plant roots hold soil and Plant roots hold soil and

sand into place. sand into place. This helps prevent This helps prevent

erosion by wind and erosion by wind and water. water.

Providence Canyon Providence Canyon formed when plants were formed when plants were removed and runoff from removed and runoff from nearby farms eroded the nearby farms eroded the land. land.

PlantsPlants

Farmers often plant clover or other cover Farmers often plant clover or other cover crops in fields they are using to grow food crops in fields they are using to grow food crops. crops.

Cover crops help return nutrients to the Cover crops help return nutrients to the soil and help prevent erosion. soil and help prevent erosion.

In some areas, farmers plant rows of trees In some areas, farmers plant rows of trees to slow wind erosion of nearby fields. to slow wind erosion of nearby fields.

This protection works naturally as well. This protection works naturally as well.

Cover Crops

PlantsPlants Along many beaches, Along many beaches,

plants grow on dunes. plants grow on dunes. The roots of these The roots of these

plants help hold the plants help hold the sand in place when sand in place when the wind blows. the wind blows.

That’s why people That’s why people should always use should always use beach crossovers beach crossovers instead of walking instead of walking across sand dunes and across sand dunes and damaging the plants. damaging the plants.