THE SPHERES OF THE
EARTH
Monday, April 13, 2015
As you can see from the previous slides the
earth is made up of a number of spheres, the
most important are:
The Atmosphere
The Lithosphere
The Hydrosphere
The Biosphere
The many spheres of the earth:
Can you name them?
The main focus of physical geography is on the LIFE
LAYER of the earth: a shallow zone of the lands and
oceans containing most of the world’s organic life
(also called Biosphere).
• All of the earth’s systems interact to support the
Biosphere.
•This is where we will begin our study of Physical
Geography.
Two diagrams illustrating the
Biosphere (life layer) of the
earth
Here is another way of looking at the
interaction between spheres.
Notice:
The Biosphere connects with all three.
The Hydrosphere
70% of the earth’s surface is covered by
water. If the earth was totally flat, earth would
be covered by water at a depth of 12,000 ft.
It fills in the lower parts of the lithosphere.
Water connects the atmosphere with the
lithosphere
Cryosphere is the frozen hydrosphere. This
even includes the frozen ground usually called
permafrost
The Atmosphere
A gaseous shell that surrounds the earth,
made mostly of oxygen, nitrogen, carbon and
hydrogen
it dictates the climate: this governs the
exchange of heat and water between the
atmosphere and the ground
Divided up into other spheres: stratosphere,
troposphere, etc.
The Lithosphere
Thin outer crust that surrounds the earth.
Platform of life
the lithosphere also supplies valuable nutrients that
pass from rock to soil to plants and finally to us.
Considered to be a brittle shell of solid rock.
Under force it could be cracked, warped , buckled.
The average depth is about 16 km
Under the oceans, depth is about 5 km
Floats on top of the Aesthenosphere (more on this
later in the course)
The Biosphere
These spheres interact with one another to create
The Biosphere or the earth’s Life Layer.
It is the biosphere that makes the earth unique
among the other planets we know of. Water in three
states.
The biosphere can be further broken down into what
are called biomes or ecozones or ecoregions.
Biomes are usually distinguished by their vegetation
cover. Biomes are really a combination of climate
regions, soil regions, vegetation regions and landform
regions.
Vertically, the habitable
zone (the biosphere)
surrounding the Earth is
extremely restricted. The
blanket of air extends to
an altitude of about 30km
and fades away into
empty space. The living
zone of the air is a layer
only 5km high.
If you compare this to the
radius of the earth it
would be the earth being
a regular sized peach and
the living zone would be
thinner than the fuzz.
On the surface of the earth, some areas are too dry, too wet, too
cold, too hot or too rugged to support human life. The most
uninhabitable areas on earth is Greenland, Antarctica and the
Arctic.
The Atmosphere is the air
we breathe. The
Hydrosphere is the water of
rivers, lakes and oceans, the
moisture in soil and air, as
well as the snow and ice of
the cryosphere. The
Biosphere is the habitat of
all earthly life. The
Lithosphere is the soil and
bedrock that cover the
Earth’s surface.
The Biosphere Cont’d
Geographers recognize five primary biome types:
•Forest
•Grassland
•Savanna
•Desert
•Tundra
These can be of course further broken down (and
depending on what book you have the names may
change).
World Biome Map – Vegetation Regions
Planet Earth, by Gary Birchall (John Wilely and Sons)
The Sun and its Role
 The catalyst that creates the biosphere from
the other spheres is the Sun.
 The sun gives the earth energy in the form of
Solar Radiation, sometimes called insolation.
 The next slide has a diagram that illustrates
how the earth distributes this energy. This
distribution is called the Earth’s Energy Balance
or Budget. Much more on this in the slide shows for Introduction #2.
Introducing Physical Geography by Strahler and Strahler.
Note: Yellow represents the energy coming from the sun. Orange
represents what is absorbed and Red represents what is released
back into space - sometimes called the albedo.
How does the Earth maintain it’s balance after a
Volcanic eruption?
How a Geography book called “Geosystems”
studies Physical Geography - our course
follows a similar pattern
 The earth either absorbs the energy and converts
it into other types of energy like:
- Fossil Fuels
- Temperature and precipitation
- Photosynthesis
- Winds and Pressure
- The Hydrologic Cycle (see picture next slide)
 Or it reflects/radiates back into space - albedo.
Introducing Physical Geography by Strahler and Strahler.
Our Earth – A System
 A good way to understand how the spheres interact
with one another is to think of the earth as a
SPACESHIP.
 Spaceships are closed systems (think of the movie
Apollo 13 or the project in Arizona called Biosphere 2,
where they actually built a closed system
(http://www.bio2.edu/). Spaceships must operate in all
kinds of environments - friendly and hostile - so they
must carry with them all the things needed to support
life:
 Air, Water, food, heat
Systems
How humans
interact in the
Earth’s
systems
Our Earth – A System
 The spaceship must recycle these things and use
them over and over in an efficient manner.
 The ship also needs an efficient waste disposal
system
 Each of these items mentioned above are vital.
They must be in perfect balance. If one of the above
should fail, then life will die.
Our Earth – Our Spaceship
The earth is like this spaceship, but only larger. The
earth is travelling in space (a hostile environment), but
it carries all the things necessary for life.
Recently the spaceship earth seems to have a crew
that doesn’t really care about maintaining these LIFE
SUPPORT SYSTEMS.
The crew takes them for granted. A few years ago,
the crew (humans) was small, our technology was
limited, our ability to damage the spaceship was also
limited.
But today, we can no longer take the systems that
make life possible on earth for granted. We have
grown to an incredible size (6 billion). Our
technology is constantly presenting new threats to
the environment:
• air pollution
• oil spills
• garbage
• waste disposal
• toxic waste
• CFCs
• carbon dioxide, etc...
We must learn all we can about these factors
that make up our life support systems. That
is where Physical Geography comes in. We
must prevent the destruction of the physical
environment.
THE FUTURE OF THE EARTH IS AT RISK!
Let’s continue our understanding of the
spaceship earth by introducing the earth.
Let’s look at the earth’s basic dimensions
and how we measure the earth and places
on the earth.
Go to the slide show entitled: Intro_Earth