S6E3.a Explain that a large portion of the Earth’s surface is water, consisting of oceans, rivers, lakes, underground water, and ice.

What you will learn in the section…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.

Match the vocabulary word to the definition.

1. Water table a. The ability of a rock or sediment to let fluids pass through its open spaces, or pores.

2. Aquifer b. The percentage of open space between individual rock particles in a rock layer.

3. Permeability c. The ground surface where water enters an aquifer.

4. Recharge zone d. A spring whose water flows from a crack in the cap rock of the aquifer.

5. Porosity e. The upper boundary of the zone of saturation.

6. Artesian spring f. A rock layer that stores groundwater and allows the flow of groundwater.

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?

It comes from water stored underground.

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

FYI (do not write)Millions of people get their water from

groundwater.Groundwater not only is an important

resource but also plays an important role in erosion and deposition.

Location of Groundwater Water is found underground in an area between

two zones. Rainwater passes through the upper zone, called the zone of aeration. Farther down, the water collects in an area called the zone of saturation. In this zone, the spaces between the rock particles are filled with water.

The two zones meet at a boundary known as the water table. Rises during wet seasons and falls during dry

seasons

AquifersThe rock layer that stores groundwater and

allows the flow of groundwater is called an aquifer.

The more open spaces, or pores, between particles in an aquifer, the more water the aquifer can hold.

The percentage of open space between individual rock particles in a rock layer is called porosity.

If the pores of a rock layer are connected, groundwater can flow through the rock layer. A rock’s ability to let water pass through is called permeability. A rock that stops the flow of water is impermeable.

The best aquifers usually form in permeable materials, such as sandstone, limestone, or layers of sand and gravel.

Some aquifers cover very large areas.They are important source of water for cities and

agriculture.

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

The size of the recharge zone depends on how permeable rock is at the surface.

Aquifer in the United States

Aquifers in Georgia

Springs and WellsGroundwater movement is determined by the

slope of the water table. Moves down slope.If the water table reaches the Earth’s

surface, water will flow out from the ground and will form a spring.

Springs are an important source of drinking water.

Where the water table is higher than the Earth’s surface, lakes will form.

Wells are human-made holes that are deeper than the level of the water table.

If it is not deep enough, it will dry up when the water table falls below the bottom of the well.

If an area has too many wells, groundwater can be removed too rapidly which can cause the wells to run dry.

Artesian SpringsA sloping layer of permeable rock sandwiched

between two layers of impermeable rock is called an artesian formation.

The permeable rock is an aquifer and the top layer of impermeable rock is called a cap rock.

Artesian spring is a spring whose water flows from a crack in the cap rock of the aquifer.

These are sometimes found in deserts, where they are the only source of water.

Most have cool water but some springs have hot water.

Formation of CavesWater erosion creates most caves found

along coastal areas. Waves crashing against the rock over years

wears away part of the rock forming a cave. Inland caves are also formed by water

erosion-in particular, groundwater eroding limestone.

As the limestone dissolves, underground passageways and caverns are formed.

The Caves of Belize Caves Branch Cave

The Caves at Norman Island

SinkholesSinkholes are common where the rock below the land

surface is limestone, carbonate rock, salt beds, or rocks that can naturally be dissolved by ground water circulating through them.

As the rock dissolves, spaces and caverns develop underground.

Sinkholes are dramatic because the land usually stays intact for a while until the underground spaces just get too big.

If there is not enough support for the land above the spaces then a sudden collapse of the land surface can occur.

The most damage from sinkholes tends to occur in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania.

Sinkhole - Guatemala330 ft deep

Nixa, Missouri60 feet in diameter and 75

feet deep