4 Earth: The Four Subsystems
WARLITO ZAMORA CANOY·FRIDAY, JUNE 23, 2017·
Origin and Structure of the Earth
ObjectiveSUBS
At the end of this lesson, you will be able to explain that the Earth consists of four
subsystems, across whose boundaries matter and energy flow.

The four subsystems of the Earth are the atmosphere, geosphere,
hydrosphere, and biosphere.
What are the characteristics of these four subsystems?

The Earth is comprised of four major subsystems. These subsystems are
also called the “spheres of the Earth.” They are atmosphere, geosphere,
hydrosphere, and biosphere.
Atmosphere

The word atmosphere comes from the Greek roots atmos which means gas,
and sphaira which means globe or ball. The atmosphere makes up of all
the gases on Earth. It extends outward about 10 000 km from the surface
of the Earth. It is composed of 78.1% nitrogen, 20.9% oxygen, 0.9% argon,
350 ppm carbon dioxide, and other components.

The atmosphere has different layers – troposphere, stratosphere,
mesosphere, thermosphere, and exosphere.

The troposphere extends to about 14.5 km above the Earth's surface. It is
the lowest layer where the weather forms.

The stratosphere is found 14.5 to 50 km above the Earth's surface. The
ozone layer that protects the Earth from the Sun's harmful UV radiation is
found in this layer.

The mesosphere extends from 50 to 85 km above the Earth's surface. It
protects the Earth from the impact of space debris.

The thermosphere is found 85 to 600 km above the Earth's surface. It has
charged particles that are affected by the Earth's magnetic field. The
particles create the Auroras or Northern and Southern lights.

The exosphere is the farthest layer. It extends to about 10 000 km above
the Earth's surface.
Geosphere

Geo is a Greek root which means ground. Geosphere includes all the soil,
rocks, and minerals present in the crust to the core of the Earth. It is
divided into three layers namely crust, mantle, and core.

The crust is the outermost layer of the geosphere. It is made mostly of
silicate materials. There are two different types of crust, the oceanic and
continental crusts. The thin oceanic crust that lies beneath the oceanic
floors is about 5 to 10 km thick. On the other hand, the thicker continental
crust that makes up the continents is about 15 to 70 km thick.

The mantle, which lies just below the crust, is made mostly of silicate rocks
rich in magnesium and iron. It is about 2900 km thick. It has increasing
temperatures at increasing depths. For instance, the layer with the lowest
temperature is the one right beneath the crust. This layer, which is soft
enough to flow, causes the plates of the crust to move. On the other hand,
the layer with the highest temperature is found in contact with the heatproducing core.

The core, which has a radius of 3400 km, is the innermost layer of the
Earth. It is made up of iron and nickel. It is the source of internal heat
because it contains radioactive materials that release energy as they decay
into more stable substances.
Hydrosphere

Hydro is a Greek root which means water.

Hydrosphere is composed of all the water on Earth in any form: water
vapor, liquid water, and ice. It is comprised of 97.5% saltwater and 2.5%
freshwater. It includes all bodies of water such as oceans, lakes, rivers, and
marshes. Clouds and rain are also part of the hydrosphere.

The water on Earth is constantly moving. It moves through the oceans in
currents. Warm waters in the tropics move toward the poles while cold
water from the polar regions move toward the tropics. Water also flows
into streams and rivers and through the rocks underground. It can also
move from the Earth’s surface to the air by evaporation and then fall back
to Earth as precipitation. It even moves into and out of the bodies of
organisms.
Biosphere

Bio is a Greek root that means life. The biosphere is comprised of all living
things. It includes all microbes, plants, and animals. It extends to the upper
areas of the atmosphere where insects and birds can be found. It also
reaches the deep parts of the oceans where marine organisms can still
survive.

Organisms interact with the other spheres to survive. Many organisms
need oxygen and carbon dioxide from the atmosphere to carry out life
processes. Water, which comprises the hydrosphere, is also important to
organisms. Finally, the rocks, soil, and minerals constitute the geosphere
also support life.
How the Earth’s Subsystems Interact

Matter and energy move and cycle between the four different subsystems.
These cycles make life on Earth possible. An example of these cycles is the
water cycle. Water moves between the different spheres. It absorbs,
releases, and transports energy around the world in its different forms.
What will happen if matter or energy does not change from one form to
another?

For example, what if water vapor does not fall back to the Earth as rain?
Then the bodies of water will be drained, and no life on Earth will exist.
Tips

Some of the components in the subsystems overlap. The most common
example is the soil which can be considered as a part of hydrosphere,
geosphere, and even biosphere. Since the soil is a complex material made
up of air, soil particles, water, and organisms, it underscores that a clear
division among subsystems cannot be drawn.
Explore

Imagine that you are part of NASA’s special mission and you are tasked to
discuss the things needed to replicate the Earth’s system in another planet.
What are the things necessary to enable life in that planet?
What do you think?

What is the importance of studying the interactions among the four
subsystems?
Key Points

The four subsystems of Earth are the atmosphere, geosphere, hydrosphere,
and biosphere.

Atmosphere makes up of all the gases in our planet.

Geosphere includes all the soil, rocks, and minerals present in the crust to
the core of the Earth.

Hydrosphere is composed of all the water on Earth in any form: water
vapor, liquid water, and ice.

Biosphere is comprised of all living things and the areas where they are
found. It includes all microbes, plants, and animals.

Matter and energy move and cycle between the four different subsystems
to make life on Earth possible.
Test Question
1. Which of the following is not included in Earth’s subsystems?

A. geosphere

B. atmosphere

C. photosphere

D. hydrosphere
2. Hydrosphere includes all the ___________on Earth.

A. water

B. landforms

C. gases

D. living things

3. Which of the following is the most abundant gas in the atmosphere?

A. oxygen

B. nitrogen

C. carbon dioxide

D. argon
4. Which of the following are included in the geosphere?

I. rock

II. mineral

III. nitrogen gas

IV. water vapor

A. I and II

B. II and III

C. III and IV

D. II and IV
5. Which of the following is true about the Earth’s subsystems?

A. Each subsystem works independently and does not depend on other
subsystems.

B. Each subsystem did not change since the formation of the Earth.

C. Earth’s subsystems interact with each other making life possible on
Earth.

D. Earth’s subsystems are similar to the subsystems of other planets.
6. Which of the following is true about the geosphere?

A. It is the habitat for some species of plants and animals.

B. It prevents the penetration of ultraviolet rays from the Sun.

C. It is the main source of water on Earth.

D. It provides oxygen needed by animals.
7. What will happen if the atmosphere on Earth is removed?

A. The Earth will be able to sustain life.

B. Ultraviolet rays will easily penetrate the Earth.

C. Solar energy will not reach the Earth’s surface.

D. The Earth will maintain its current temperature.
8. All of the following is true about the interaction of the biosphere with other
subsystems, except _____________.

A. Organisms in the biosphere form parts of the geosphere when they
decompose into smaller substances.

B. Organisms in the biosphere maintain the balance of gases in the
atmosphere through consumption and excretion of gases.

C. Organisms in the biosphere increase the amount of water in the
hydrosphere.

D. Organisms in the biosphere consume water from the hydrosphere for
survival.
9. How does the atmosphere support other subsystems?

I. It supplies organisms the needed oxygen and carbon dioxide.

II. It absorbs all the minerals and nutrients from the geosphere.

III. It serves as a reservoir for water vapor.

IV. It shapes the Earth’s landforms by its constant movement as the wind.

A. I and II

B. I, II and III

C. II, III and IV

D. III and IV
10. Which of the following are true about the hydrosphere?

I. Ice and water vapor suspended in the atmosphere are included in the
hydrosphere.

II. Freshwater is greater than the amount of saltwater on Earth.

III. The water on Earth is constantly moving.

IV. Water can move from the Earth’s surface to the air by precipitation and
then fall back to Earth by evaporation.

A. I only

B. I and II

C. I and III

D. III and IV AN
In MELC, this topic is under Module 2.