The document discusses the hydrosphere, specifically water on Earth. It covers the basics of water molecules, the water cycle, oceans, and other bodies of water. The key points are: - Water (H2O) covers 70% of Earth's surface and is made up of two hydrogen atoms and one oxygen atom. - The water cycle constantly moves water around Earth through processes like evaporation and precipitation. - The oceans are the largest part of Earth's hydrosphere, covering over 70% of the planet. The four major oceans are the Pacific, Atlantic, Indian, and Arctic oceans. - Other bodies of water include lakes, rivers, ice caps, and groundwater, which

2. THE HYDROSPHERE
Scientists generally divide our little blue world into 4 separate yet
overlapping spheres.
These spheres are the lithosphere, the atmosphere, the biosphere, and
the hydrosphere.
In this unit we will explore the Earth’s hydrosphere.
The hydrosphere plays a very important role in the evolution
of life, as well as in weather and erosion.

3. What Is Water?
Have you ever heard someone refer to water as
H2O?
Water is a basic molecule made up of two hydrogen
atoms and one oxygen atom.
 When these three atoms come together, they form
a strong bond that is difficult to break. The strength
of this bond keeps a water molecule together for
millions and even billons of years

4. WATER COVERS 70% OF THE
SURFACE OF THE EARTH
Water is one of the most
common substances on
the Earth.
Covering over 70% of the
surface of the Earth, it is
easy to find.
Scientists believe that the amount of water that is on the Earth today
is the same amount that was on the Earth during the reign of the
dinosaurs

5. WATER IS VERY IMPORTANT FOR
LIFE
 Why is water so important to life? It has some unique properties
such as:
 it is the only substance on Earth that is in liquid form at the
temperatures commonly found on the Surface of our planet.
 it is a superb solvent, meaning that other substances regularly
and easily dissolve into it. This allows water to carry nutrients to
cells, and carry waste away from them.
 water has the unique property of expanding as it freezes. Because water
expands becoming less dense, frozen water, more commonly known as
ice, floats. This is very important because it protects the water
underneath, insulating it from freezing.
Imagine what would happen if water became more dense? It would
sink, allowing another layer of water to freeze. Eventually all the
water across the entire surface of our planet would freeze, making
life impossible.

6. THE WATER CYCLE
While the total amount of water on Earth remains relatively constant,
the appearance of this water changes from moment to moment. Water
is constantly in motion. The chief process responsible for moving
water around the Earth is the hydrologic cycle.

7. THE
EARTH’S
OCEANS

8. OCEANS DIVIDED
There are 4 main oceans:
The Pacific Ocean, The Atlantic Ocean,
The Indian Ocean and the Arctic Ocean.

9. As you can see these oceans are connected,
forming one large ocean.
Water from one of the four oceans is free to move
into another ocean.
Whales, fish, and other life forms from one ocean
are free to travel to another.

10. THE PACIFIC OCEAN
The largest . It covers twice as much space as any other
ocean, and more space than all the continents put
together.
This vast body of water extends upward, touching the
Arctic ocean, and also extends down to the shores of
Antarctica. The bulk of this ocean, however, lies along
the warm tropics. This makes the majority of the Pacific’s
water warm.
The Pacific Ocean has the deepest average depth, and is
also home to the deepest trenches on Earth. Much of the
Pacific is dotted with small volcanic islands, such as
Hawaii, Tonga and Samoa.
The Pacific Ocean is notorious for bad weather.

11. THE
PACIFIC
OCEAN

12. THE ATLANTIC OCEAN
The Atlantic Ocean stretches from the Arctic Ocean
downward to the shores of Antarctica. This makes it
the same size from north to south as the Pacific
Ocean. However, from east to west, the Atlantic
Ocean is only about half as wide as the Pacific.
The Atlantic Ocean is a deep ocean. Its average depth
is just slightly less than that of the Pacific Ocean. This
ocean has far fewer islands than the Pacific.

13. THE
ATLANTIC
OCEAN

14. THE INDIAN OCEAN
 The Indian Ocean lies between Africa on the west,
Australia on the east, Asia on the north, and
Antarctica on the south.
90% of this ocean lies to the south of the Equator.
The Indian Ocean is just slightly less deep than the
Atlantic Ocean.

15. THE
INDIAN
OCEAN

16. THE ARCTIC OCEAN
The Arctic Ocean is both much smaller than the
other oceans as well as more shallow. This ocean is
connected to the Pacific and Atlantic Oceans via
small gaps between continents.
This ocean is also much colder than the majority of
the other oceans, with much of the water covered in
a frozen ice cap.

17. THE
ARCTIC
OCEAN

18. CHARACTERISTICS OF OCEAN
WATER
The ocean can extend in some
places down to depths of
several kilometers. However,
most of the action takes place in
the first couple hundred meters.
Below this depth it is too dark,
cold and murky for much to
happen.
Above this depth, where sunlight reaches, characteristics such as
temperature, turbulence, and salinity (the amount of salt)
can be very different from location to location.

19. OCEAN´S SALINITY
By far, the most common mineral found dissolved in sea water is salt.
The salinity of the oceans can vary greatly from location to location.
This salinity is dependent on two important factors. Firstly, the amount
of evaporation taking place; and secondly, the amount of fresh water
being added.
As water evaporates, it leaves the salts and other minerals behind.
This causes the water left behind to be more salty. As fresh water is
added, either via rivers or via rainfall, the salinity of the ocean in a
particular location is decreased.
Minerals, can dissolve quickly and
easily into water.
The ocean contains many different
minerals found across the surface of
the Earth, all dissolved into the water.
These minerals make up about 3.5% of
the total volume of the Earth’s oceans.

20. WATER TEMPERATURE
 As one would expect, the further you travel from the
Equator, the colder the ocean waters generally
become. Near the Equator, surface water
temperatures can be as high as 27° . Near the poles,
the temperature drops to a chilly -2°.
The western side of oceans are usually warmer than
the eastern side. This is due to the way in which both
the atmospheric and oceanic currents move water
from the equator towards the poles on the western
side of oceans, and from the poles towards the
equator on the eastern side of oceans.

22. MOVEMENT OF OCEAN WATER
The waters of the Earth’s oceans are for the most part in liquid
form. What happens when you take a half full bottle of water
and shake it up? Do you see the bubbles swirling rapidly
around inside the water bottle?
The waters of the Earth’s oceans can be mixed up by a
number of forces, including wind, splashing against a rocky
shore, swimmers, boats, etc. However, the items mentioned
above create only a very minimal amount of mixing. Three
important forces create a much more prevalent mixing of the
ocean’s waters, causing the water to move about from one
place to another, as though a giant were shaking them in the
same manner that you shake a water bottle.
These forces are waves, currents, and ocean tides.

23. OCEAN WAVES

24. OCEAN WAVES
The surface of the Earth’s oceans is in constant
motion, moving up and down in the form of waves. If
you have been to a beach, you have witnessed waves
first hand.
Waves form as energy is transferred from molecule to
molecule across the surface. In general, the water
molecules move very little. It is only the energy that
actually moves.
However, as waves break across a shore or crash in
violent storms, they can be the source for great
mixing of an ocean’s water.

25. OCEAN CURRENTS

26. OCEAN CURRENTS
There are a number of ocean currents found around
the Earth.
 A current is like a vast river within the ocean, flowing
from one place to another. These currents are caused
by differences in temperature, differences in salinity,
and by wind. Currents are responsible for a vast
amount of movement of the water found in the
Earth’s oceans.

27. TIDES
Tides are caused by the gravity
of the Moon and Sun. Attracted
by gravity, causing water levels
to rise and fall. Typically water
will rise for about six hours,
followed by six hours of falling
water depths.
By far the most important factor affecting the movement of
water across the ocean is the tides.

28. THE EARTH’S ICE
Second only to the ocean in the amount of water storage, the ice of
the Earth makes up more than twice as much water as all other
types of water storage, including ground water, lakes, streams, etc.
 It has been estimated that there is enough water locked up in the
form of ice to sustain all the rivers and streams of the Earth for nearly
1,000 years.
This ice is found around both the North and South Poles, and is
always fresh. This is because, regardless of whether it formed by
freezing rain or sea water, the salt is not taken into the ice crystals
as they form.
 In addition to the vast ice caps found at the top and bottom of the
Earth, there are also vast amounts of frozen water underground.
This frozen soil is known as permafrost, and is found in Canada,
Alaska and Siberia.

30. SURFACE WATER
Water found on the surface of continents and islands
is referred to as surface water.
 Surface water makes up only one fourth of one
percent, or 0.25%, of the total water found on Earth.
This water is found in rivers, streams, lakes, springs
and swamps, and is extremely important to the lives
of all land animals, including humans.

32. LAKES
 Lakes contain about 90% of all the surface water found on Earth
(not including oceans). Lakes form when water finds its way into a
basin. In order to continue existing, lakes must have a continual
source of new water, otherwise they will eventually dry up.
Most lakes contain fresh water. However, in some cases, the water
found in a lake can become salty, just like the ocean. This happens
when a lake does not have a stream, either above ground or
underground, draining water away from it. As water enters a lake, it
carries minerals with it. As this water dissolves, it leaves the minerals
behind.
Most lakes only last a few thousand years and then disappear. This
is because as streams and rivers carry water into the lake, they also
carry sediment. This sediment slowly fills the lakes.

33. Many lakes are man made. These are referred to as reservoirs.
Reservoirs allow cities and nations to store water for later use. Most of
these reservoirs are small in size, but some are very large, spanning
several hundred miles, or kilometers.

34. SWAMPS
A swamp is similar to a lake but it is much shallower.
Swamps are covered with water, but this water is
shallow enough to allow plants to grow, reaching the
surface.
Swamps are generally dominated by water tolerant
trees.

36. MARSHES
Marshes are similar to swamps, but instead of trees
they are dominated by grasses and reeds. They are
generally rich with life, housing many kinds of frogs,
turtles, fish, and bird life.

38. RIVERS AND STREAMS
Geographers generally refer to all rivers and streams as streams,
regardless of how big they are.
Streams have an important job.
They drain the landscape, and move water and minerals towards the Earth’s
oceans.
As water drains, it generally begins in small creeks, which flow into larger and
larger streams, and eventually into powerful flowing rivers.
The largest river on Earth is the Amazon, which drains much of South
America.
The largest river in North America is the Mississippi River, which drains over
40% of that continent.

40. UNDERGROUND WATER
Locked deep within the lithosphere, or surface of the
Earth, is found many billions of gallons of water.
Almost anywhere on Earth, it is possible to dig down
and find a supply of fresh drinkable water. Almost all
of this water was deposited over millions of years by
the many rain and snow storms that have visited the
surface of the Earth
Most ground water lies within 0.8km of the surface of
the Earth. However, scientists have found water at a
depth of more than 10km.