Transcript 23.1 Fresh Water - Madison Local Schools

23.1 Fresh Water
Earth’s Water
Earth is the only
planet with liquid
water at its
surface.
Oceans
97.2%
Glaciers
2.1%
Other
0.7%
(including water vapor,
groundwater, lakes,
and rivers)
23.1 Fresh Water
If you could look at Earth from space, you
would see that most of its surface—about 71
percent—is covered with water.
The temperature range on Earth allows water
to occur in three states: liquid, solid, and gas.
Most of Earth’s water is the salt water found in
the oceans.
23.1 Fresh Water
Only about three percent of Earth’s water is
fresh.
• Most of this fresh water occurs as ice and snow
in Earth’s high mountains and polar regions.
• Most of Earth’s liquid fresh water is in the form of
groundwater, the water found underground.
• Smaller amounts of fresh water are found in
lakes and streams and as water vapor or clouds
in the atmosphere.
23.1 Fresh Water
The Water Cycle
What processes are involved in the water
cycle?
The water cycle is made up of several
processes, including evaporation,
transpiration, condensation, precipitation,
and the eventual return of flowing water to
the ocean.
23.1 Fresh Water
The Water Cycle
The continuous movement of water among the
oceans, atmosphere, and land is called the
water cycle.
The energy of sunlight and the force of gravity
power the water cycle.
23.1 Fresh Water
The Water Cycle
Water is constantly moving through the water
cycle.
Condensation
Precipitation
Transpiration
Evaporation
Groundwater
Runoff
23.1 Fresh Water
The Water Cycle
Evaporation
Solar energy causes water on Earth’s surface to
evaporate. Warm, moist air rises, carrying the
water vapor higher into the atmosphere.
• Evaporation occurs over the ocean and large lakes,
streams, ponds, and other sources.
• Water vapor also enters the atmosphere from plants in
a process called transpiration.
23.1 Fresh Water
The Water Cycle
Condensation
As warm air rises, it expands and cools. Colder air
can hold less water vapor than warm air, so
condensation occurs.
Billions of water droplets or ice crystals make up
clouds.
23.1 Fresh Water
The Water Cycle
Precipitation
When the water droplets or ice crystals in clouds
get too heavy, gravity causes them to fall to the
ground as precipitation—rain, snow, sleet, hail, or
freezing rain.
Worldwide, the rates of evaporation and
precipitation are balanced.
23.1 Fresh Water
The Water Cycle
Completing the Cycle
A single molecule of water moves between the
surface and atmosphere many times.
• About 90 percent of the water that evaporates from
the oceans falls back into the oceans.
• Most precipitation that falls on land quickly returns to
the atmosphere through evaporation and transpiration.
23.1 Fresh Water
The Water Cycle
• Water seeps into the soil as groundwater or
becomes frozen in glaciers. A glacier is a
large mass of moving ice and snow on land.
• Some water that falls on land flows into
streams before it returns to the ocean.
23.1 Fresh Water
Fresh Water
Where is Earth’s fresh water found?
A small portion of Earth’s fresh water is
located in the atmosphere, streams, and
lakes. Most is located in groundwater and
glaciers.
23.1 Fresh Water
Fresh Water
Only a small portion of the water on Earth
exists as fresh water.
Fresh water is relatively free of minerals and
salts.
23.1 Fresh Water
Fresh Water
The Atmosphere
A tiny percentage of Earth’s fresh water is found in
the atmosphere as water vapor or clouds.
Water vapor stays in the atmosphere for just a
short time—a few hours or a few days.
23.1 Fresh Water
Fresh Water
Streams and Rivers
Streams and rivers contain even less fresh water
than the atmosphere.
A great deal of water passes through streams,
making them very important in shaping the surface
of the land.
23.1 Fresh Water
Fresh Water
Runoff is water that flows over Earth’s surface.
• Runoff and some groundwater flow into streams.
• Streams flow together to form a network, called a
river system.
• A major river has many smaller streams, called
tributaries, that flow into it.
The area of land that contributes water to a
river system is called a watershed.
23.1 Fresh Water
Fresh Water
The Mississippi River watershed covers most
of the central United States.
23.1 Fresh Water
Fresh Water
Ponds and Lakes
Ponds and lakes form in depressions in the land.
• Lakes form in large, deep depressions.
• Ponds form in smaller depressions and tend to be
smaller and shallower than lakes.
23.1 Fresh Water
Fresh Water
Ponds form when water
collects in small, shallow
depressions. Many ponds
support lush plant growth
and animal life.
23.1 Fresh Water
Fresh Water
Water Beneath the Surface
About a quarter of all fresh water is groundwater.
• Close to the surface, the pore spaces in rock and soil
are filled with air.
• Deeper below the surface is the saturated zone, a
region where the pore spaces are entirely filled with
groundwater.
23.1 Fresh Water
Fresh Water
• The top of the saturated zone is called the
water table.
• Water flows slowly from high elevations of
the water table to low elevations.
• Lakes and streams are usually found where
the ground is below the water table.
23.1 Fresh Water
Fresh Water
Groundwater makes up about one quarter of
all fresh water. In the saturated zone,
groundwater flows in the pore spaces in
underground rock.
Aquifer
Saturated zone
Spring
Impermeable layer
Water table
Saturated zone
Well
23.1 Fresh Water
Fresh Water
A rock is permeable if water can easily pass
through it. Rocks like sandstone and limestone
are permeable.
A permeable rock layer that is saturated with
water is called an aquifer. Aquifers are refilled,
or recharged, as rainwater seeps into them.
23.1 Fresh Water
Fresh Water
Rocks are impermeable if water cannot easily
pass through them.
• Shale and unbroken granite are examples of
impermeable rock.
• Groundwater in loose rock or soil above an
impermeable layer may flow out of a hillside as a
spring.
23.1 Fresh Water
Fresh Water
Glaciers and Icebergs
Glaciers form in areas where more snow falls than
melts each year.
• As snows build up, the weight of the snow presses on
the layers below, changing them to ice.
• When the weight of the snow is great enough, glaciers
begin to flow slowly downhill.
23.1 Fresh Water
Fresh Water
• Ice is added at the top of the glacier through
snowfall.
• Ice is removed from the glacier by melting,
sublimation, and the formation of icebergs.
• Icebergs are large pieces of ice that break off
when a glacier reaches the ocean.
23.1 Fresh Water
Fresh Water
Icebergs are formed when a piece of a glacier
breaks off into the ocean. Icebergs are made
of fresh water.
23.1 Fresh Water
Assessment Questions
1. During which part of the water cycle do water
molecules gain energy?
a.
b.
c.
d.
runoff
condensation
evaporation
precipitation
23.1 Fresh Water
Assessment Questions
1. During which part of the water cycle do water
molecules gain energy?
a.
b.
c.
d.
runoff
condensation
evaporation
precipitation
ANS: C
23.1 Fresh Water
Assessment Questions
2. What is an aquifer?
a. the area of land that contributes water to a river system
b. the underground line separating saturated regions from
unsaturated regions
c. a rock that water cannot easily pass through
d. a rock layer saturated with water
23.1 Fresh Water
Assessment Questions
2. What is an aquifer?
a. the area of land that contributes water to a river system
b. the underground line separating saturated regions from
unsaturated regions
c. a rock that water cannot easily pass through
d. a rock layer saturated with water
ANS: D