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divided into three major parts: the water portion of our planet, the hydrosphere; Earth’s
gaseous envelope, the atmosphere; and, of course, the solid Earth, or geosphere. It
needs to be emphasized that our environment is highly integrated and is not dominated
by rock, water, or air alone. It is characterized by continuous interactions as air comes in
contact with rock, rock with water, and water with air. Moreover, the biosphere, which
is the totality of all plant and animal life on our planet, interacts with each of the three
physical realms and is an equally integral part of the planet. Thus, Earth consists of four
major spheres: the hydrosphere, atmosphere, geosphere, and biosphere.
The hydrosphere is a dynamic mass of water that is continually on the move,
evaporating from the oceans to the atmosphere, precipitating back to the land, and
running back to the ocean again. The global ocean is certainly the most prominent
feature of the hydrosphere, blanketing nearly 71% of Earth’s surface to an average
depth of about 3800 m. It accounts for about 97 % of Earth’s water. The hydrosphere
also includes the freshwater found underground and in streams, lakes, and glaciers.
Moreover, water is an important component of all living things.
Earth is surrounded by a life-giving gaseous envelope called the atmosphere.
This thin blanket of air is an integral part of the planet. It not only the air that we breathe
but also acts to protect us from the Sun’s intense heat and dangerous ultraviolet
radiation. The energy exchanges that continually occur between the atmosphere and the
surface and between the atmosphere and space produce the effects we call weather and
climate.
The biosphere includes all life on Earth. Ocean life is concentrated in the sunlit
surface waters of the sea. Most life on land is also concentrated near the surface, with
tree roots and burrowing animals reaching a few meters underground and flying insects
and birds reaching a kilometre or so above Earth. A surprising variety of life forms are
also adapted to extreme environments. Plants and animals depend on the physical
environment for the basics of life. However, organisms do not just respond to their
physical environment. Indeed, the biosphere powerfully influences the other three
spheres. Without life, the makeup and nature of the geosphere, hydrosphere, and
atmosphere would be very different.
Beneath the atmosphere and the oceans is the solid Earth, or geosphere. The
geosphere extends from the surface to the center of the planet, a depth of 6400 km,
making it by far the largest of Earth’s four spheres. By examining the most prominent
surface features and their global extent, we can obtain clues to the dynamic processes
that have shaped our planet.

Task 3. Look at Figure 1.2. Try to analyze what kind of Earth’s water
clearly dominates. Considering only the nonocean component count the percent of
Earth’s fresh water. How much does the groundwater account for?

Task 4. Fill in the gaps with one of the suitable words:

a) physical geology, geology, historical geology
… means “the study of Earth.” The two broad areas of the science of geology
are …, which examines the materials composing Earth and the processes that operate
beneath and upon its surface; and…, which seeks to understand the origin of Earth and
its development through time.

b) biosphere, atmosphere, hydrosphere, geosphere
Soil, the thin veneer of material at Earth’s surface that supports the growth of
plants, may be thought of as part of all four spheres. The solid portion is a mixture of
weathered rock debris (…) and organic matter from decayed plant and animal life (…).

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