1. Chapter 4, Section 2 The Hydrosphere
Focus questions:
In what forms and where do we find water on Earth?
What are the causes and effects of floods?

2. Water on Earth Water is one of our most important resources
Humans can’t survive more than a week without it

3. Water is a valuable power resource
Hydroelectricity - when water drives turbines to produce electricity

4. Water provides a valuable transportation network of rivers, lakes, and oceans

5. Characteristics of water…
Water is the only substance on earth that exists as a liquid, a solid, or a gas in earth’s temperature range

6. Water has the ability to dissolve almost anything over time
Water heats and cools very slowly
Moderates the temperature on earth’s surface
Winter, south coast of Iceland

7. Fresh water is unevenly distributed on earth’s surface

8. 97% of water is in the oceans – unusable…why?

9. Seawater contains traces of every known element on earth
Salts are the most common thing found in seawater
Seawater is 3.5% salt – way too salty to drink

10. Desalinization (desalination)
Very simple process
boil the water, condense the steam
back into water
(minus the salt)
Very expensive, uses lots of energy

11. 2% of earth’s water is in the polar ice caps – unusable…why?
North Pole
2% of earth’s water is in the polar ice caps – unusable…why?
South Pole

12. Less than 1% of earth’s water is fresh (a.k.a. sweet) water
Found in rivers, streams, lakes, and also undergound (groundwater)
A small amount found in the atmosphere (clouds) and in plants & animals

13. Hydrologic (a.k.a. Water) Cycle
The circulation of water through the hydrosphere
Hydrosphere –
all of the
water on
the planet
Driven
by solar
energy

14. Step 1 – Evaporation Step 2 – Condensation Step 3 – Precipitation
Most water in the atmosphere evaporates from the oceans
Step 2 – Condensation
As rising air cools, water vapor condenses into tiny droplets, which then form clouds
Step 3 – Precipitation
Rain, snow, etc.

15. Some precipitation falls as snow in mountains or polar areas

16. Some precipitation falls as rain and…
flows off to rivers, streams, or lakes (called surface runoff)
is absorbed into the ground, (called groundwater)

18. Surface water Headwaters
Formed from runoff of precipitation down the slopes of hills and mountains
The first and smallest streams to form from this runoff

19. Tributaries
Any smaller streams or rivers that flow into a larger stream or river

20. Watershed (a.k.a. Drainage Basin)
An area of land drained by a river and its tributaries

21. The Mississippi River Watershed covers over 1.2 million square miles

22. Lakes are formed when runoff fills a depression on the land surface
Lakes form in different ways
In depressions left by receding glaciers (ex. Great Lakes)

23. In Rift Valleys where continents are pulling apart (ex
In Rift Valleys where continents are pulling apart (ex. Dead Sea between Israel and Jordan)
The Dead Sea is so salty that you can float on your back and read a newspaper

24. An estuary may form where a river meets the sea
A semi-enclosed body of fresh water and saltwater
Rich in fish and shellfish

25. Wetlands are land areas that are flooded for at least part of the year
Some of the earth’s most productive lands, with huge populations of fish, shellfish, and birds
Also filters pollutants from the water

26. Groundwater Large freshwater resource beneath the surface of the land
Comes from
precipitation
Water seeps
down and
collects in
tiny spaces
between
rocks and
soil

27. Top of the saturated zone is called the water table
Water table may be near surface if climate is wet, or far below if climate is dry
Wells must be drilled well below the water table to access this resource. Why?
Well
Water Table

28. Floods
Occur when rivers carry more water than the channel can hold

29. Flooding is natural, but human activity can make floods worse
Removing vegetation and paving over land speeds up surface runoff

30. Flood damage is often increased because people choose to live near rivers

31. Floodplains make good farmlands
Why?

32. People have been trying to control floods for thousands of years, with some success
The rivers always win in the end