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THE SPHERES OF THE EARTH. Tuesday, April 1, 2014. 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?.

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the spheres of the earth


Tuesday, April 1, 2014


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 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.

Here is another way of looking at the interaction between spheres.


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 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.

Our Earth – A System

  • Agood 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 ( 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

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.



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