The environment can be divided into four segments, also
known as "spheres", each representing a different part of the planet.
These spheres interact with each other, and changes in one can affect the
others. The four segments are:
- Atmosphere:
This is the layer of gases that surrounds the Earth, held in place by
gravity. It is composed mostly of nitrogen and oxygen, but also contains
smaller amounts of other gases like carbon dioxide and argon. The
atmosphere plays a crucial role in supporting life on Earth, protecting it
from extreme temperatures and harmful solar radiation, and facilitating
the water cycle and weather patterns.
- Hydrosphere:
This includes all of Earth's water, found in oceans, seas, lakes, rivers,
underground as groundwater, in the atmosphere as water vapor, and locked
in ice caps and glaciers. About 71% of the Earth's surface is covered by
water, with the vast majority being salt water in the oceans. The
hydrosphere plays a vital role in supporting life, as water is essential
to all known forms of life.
- Lithosphere:
This comprises the Earth's outer solid shell, including the crust and the
uppermost part of the mantle. It ranges from about 5 kilometers in depth
in the oceanic crust to about 70 kilometers in the continental crust. The
lithosphere is broken up into large pieces called tectonic plates, whose
movements can cause earthquakes, volcanic activity, and the creation of
mountain ranges.
- Biosphere:
This is the part of the Earth where life exists, from the deepest parts of
the oceans, to the highest mountains, to the skies above. It encompasses
all living organisms, including humans, and the physical environments they
inhabit. The biosphere is a complex, interconnected web of life, and
changes in one part of the biosphere can have far-reaching effects on
other parts.
These segments of the environment are not isolated from each
other; they interact in numerous ways. For instance, the water cycle is a
constant exchange of water between the hydrosphere, atmosphere, and
lithosphere. Similarly, living organisms in the biosphere affect and are
affected by conditions in the other three spheres. The study of these
interactions and their impacts is a central part of environmental science.