Earth Science: Book H, Chapter 1

Section 1: The Active RiverBy the end of this section, you should be able to:

Describe how moving water shapes the surface of the Earth by the process of erosion.

Explain how water moves through the water cycle.

Describe a watershed.

Explain three factors that affect the rate of stream erosion.

Identify four ways that rivers are described.

Erosion

Erosion is the process by which soil and sediment are transported from one location to another.

Water is a major agent of erosion. Rivers often carry eroded materials long distances.

Water Cycle

The water cycle is the continuous movement of Earth’s water from the ocean to the atmosphere to the land and back to the ocean.

The water cycle is driven by energy from the sun.

River Systems

A stream that flows into a lake or into a larger stream is called a tributary.

A watershed, or drainage basin, is the area of land that is drained by a water system.

Watersheds are separated from each other by areas of higher ground called divides.

Stream Erosion As a stream forms, it erodes rock and soil to create

a channel. The channel is the path that the stream follows.

Streams start out with narrow and steep channels. Over time the channels become wider and deeper.

When streams become longer and wider, they are called rivers.

Stream Erosion Gradient is the measure of the change in elevation

over a certain distance.

Calculating a Stream’s Gradient

Math Practice on p.7

Stream Erosion The amount of water that a stream or river carries

in a given amount of time is called discharge.

Stream Erosion The materials carried by a stream are called the

stream’s load.

Stages of a River

A youthful river erodes its channel deeper rather than wider. These rivers have steep gradients, few tributaries, and can include rapids and waterfalls.

A mature river erodes its channel wider rather than deeper. They have gradients that are not as steep with fewer falls and rapids. Mature rivers do have more discharge than a youthful river.

Stages of a River

An old river has a low gradient and little erosive energy. These rivers deposit rock and soil in and along its channel. They also have wide, flat flood plains and many bends.

Rejuvenated rivers are found where the land is raised by tectonic activity.

Section Review

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Warmup

Even though flooding along rivers is potentially harmful, many farms are located near rivers.

Why do people build farms along rivers?

Section 2: Stream & River Deposits

By the end of this section, you should be able to:

Describe the four different types of stream deposits.

Describe how the deposition of sediment affects the land.

Deposition in Water Rivers can act as a type of liquid conveyor belt to

carry fertile soil to farmland and wetlands.

After rivers erode soil and rock they deposit their load downstream.

The rock and soil deposited by streams is called sediment.

Deposition is the process in which material is laid down or dropped.

Deposition in Water Heavy minerals are sometimes deposited at places

in a river where the current slows down.

This kind of sediment is called a placer deposit.

Deposition in Water As its current slows, a river often deposits its load

in a fan-shaped pattern called a delta.

A delta is made mostly of mud and these mud deposits form new land and cause the coastline to grow.

Deposition on Land Fast-moving mountain streams slow down very

quickly when they flow onto a flat plain.

These streams deposit their sediment in a fan-shape called an alluvial fan. These deposits form on dry land.

Think/Pair/Share

Compare and contrast deltas and alluvial fans.

Where is sediment deposited?

Deposition on Land The area along a river that forms from sediment

deposited when a river overflows its banks is called a floodplain.

Floodplains contain rich farmland due to the periodic flooding that brings new soil to the land.

Deposition on Land

Floods can damage property and cause a loss of lives. Dams and levees are often used to prevent flooding.

Section Review

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Modeling Watersheds Lab

How does water get into a river?

Water always flows ____________?

Warmup

A family lives 50 km from the nearest stream or lake and gets water from a well.

Where does the water in the well come from?

Section 3: Water UndergroundBy the end of this section, you should be able to:

Identify and describe the location of the water table.

Describe an aquifer.

Explain the difference between a spring and a well.

Explain how caves and sinkholes form as a result of erosion and deposition.

Water Underground

Groundwater is the water located within the rocks below the Earth’s surface.

It not only is an important resource but it plays an important role in erosion and deposition.

Location of Groundwater The zone of aeration and the zone of saturation

meet at a boundary known as the water table.

Aquifers

An aquifer is a body of rock or sediment that stores groundwater and allows the flow of groundwater.

Did You Know?

Geologists estimate that aquifers hold 50 million cubic kilometers of fresh water worldwide.

There is about 20 times more water underground than in the atmosphere and all of the rivers and lakes combined.

Aquifers The percentage of open space between individual

rocks is called porosity.

Porosity depends on the differences in sizes of the particles that make up the rock layers.

A rock’s ability to let water pass through is called permeability.

The larger the particles, the more permeable the rock layer is due to less friction.

Aquifers The best aquifers usually form in permeable

materials.

The ground surface where water enters an aquiferis called the recharge zone.

The size of the recharge zone depends on the permeability of the surface.

Water Conservation

In the United States, water use has been reduced 15% over the last 20 years.

How do you think this has happened?

Springs and Wells A spring is where the water table has reached

Earth’s surface and water is flowing out of the ground.

Springs can be important sources of what?

Springs and Wells

In areas where the water table is higher than Earth’s surface, a lake will form.

Springs and Wells An artesian spring is a spring whose water flows

from a crack in the cap rock of an aquifer.

Springs and Wells A human-made hole that is deeper than the level

of the water table is called a well.

Underground Erosion & Deposition Groundwater can cause erosion by dissolving rock.

Although caves are formed by erosion, they also show signs of deposition, such as stalactites and stalagmites.

Underground Erosion & Deposition When the water table lowers, the roofs of caves

are no longer supported by the water underneath. The roof of a cave can then collapse, which leaves a circular depression called a sinkhole.

Section Review

p.21 #2-11

Warmup

While hiking, you realize your water bottle is almost empty.

Why should you not fill your bottle with water from the nearest stream?

Section 4: Using Water WiselyBy the end of this section, you should be able to:

Identify two forms of water pollution.

Explain how the properties of water influence the health of a water system.

Describe two ways that wastewater can be treated.

Describe how water is used and how water can be conserved in industry, in agriculture, and at home.

Our Fresh Water Our bodies are almost 65% water.

Only 3% of Earth’s water is drinkable.

Of that 3%, 75% is frozen in the polar ice caps.

WE MUST PROTECT OUR WATER RESOURCES!

Water Pollution

Pollution is the introduction of harmful substances into the environment.

Pollution that comes from one specific site is called point-source pollution.

Nonpoint-source pollution is pollution that comes from many sources.

Health of a Water System Fish and other organisms that live in water need

dissolved oxygen in the water to live.

Elevated nitrate levels in water can be harmful to organisms because they lower the amount of dissolved oxygen in the water.

Alkalinity refers to water’s ability to neutralize acid. Acid rain can lower water’s alkalinity.

Cleaning Polluted Water

Where does our waste water go?

Sewage treatment plants are facilities that clean the waste materials out of water.

They also protect the environment from water pollution and protect us from diseases that could be easily transmitted through dirty water.

Cleaning Polluted Water

In primary treatment, dirty water is passed through a large screen to catch solid objects.

In secondary treatment, the water is sent to an aeration tank, where it is mixed with oxygen and bacteria.

Cleaning Polluted Water A septic tank is a large underground tank that

cleans wastewater from a household.

Where the Water Goes

About 19% of water used in the world is used for industrial purposes.

Water must be used in agriculture to facilitate plant growth.

Many people save water by installing low-flow shower heads and low-flush toilets.

How Do You Use Water? The average household in the United States uses

about 100 gallons of water per day.

Section Review

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