earth and life science

Unit 1 Lesson 1 Earth’s Spheres
Copyright © Houghton Mifflin Harcourt Publishing Company

What on Earth?
What is the Earth system?
• A system is a group of related objects or parts
that work together to form a whole.
• The Earth system is all of the matter, energy,
and processes within Earth’s boundary.
• Earth is a complex system made of living and
nonliving things, and matter and energy
continuously cycle through the smaller systems.

What is the geosphere?
• The geosphere is the mostly solid, rocky part of
Earth. It extends from the center of Earth to the
surface of Earth.
• The thin, outermost layer of the geosphere is
called the crust. It is made mostly of silicate
minerals.
• Oceanic crust is 5 to 10 km thick. Continental
crust is 35 to 70 km thick.

• The mantle is the layer that lies below the crust. It
is about 2,900 km thick.
• The mantle is made of very slow-flowing, solid
rock, consisting of silicate minerals that are
denser than the silicates in the crust.
• Earth’s central part, called the core, has a radius
of about 3,500 km. It is made of iron and nickel
and is very dense.

• Describe the characteristics of the layers of Earth.

Got Water?
What is the hydrosphere?
• The hydrosphere is the part of Earth that is
liquid water.
• Oceans, lakes, rivers, marshes, groundwater, rain,
and the water droplets in clouds are part of the
hydrosphere.
• Water on Earth is constantly moving. It even
moves into and out of living things.

What is the cryosphere?
• The cryosphere is made up of all of the frozen
water on Earth.
• Snow, ice, sea ice, glaciers, ice shelves, icebergs,
and permafrost are all part of the cryosphere.
• Changes in the cryosphere can play an important
role in Earth’s climate and species’ survival.

What a Gas!
What is the atmosphere?
• The atmosphere is a mixture of mostly invisible
gases that surround Earth.
• It extends outward about 500 to 600 km from
Earth’s surface, but most of the gases lie within 8
to 50 km of Earth’s surface.
• The atmosphere is about 78 percent nitrogen, 21
percent oxygen, and 1 percent many other gases.

• Minor gases in the atmosphere include argon,
carbon dioxide, and water vapor.
• The atmosphere contains the air we breathe.
• It also traps some energy from the sun, which
helps keep Earth warm enough for living things to
survive and multiply.

• Some gases of the atmosphere absorb and reflect
harmful ultraviolet (UV) rays from the sun,
protecting Earth and its living things.
• The atmosphere also causes space debris to burn
up before reaching Earth’s surface and causing
harm.

What is the biosphere?
• The biosphere is made up of living things and the
areas of Earth where they are found.
• Organisms usually need oxygen or carbon dioxide
to carry out life processes.
• Liquid water, moderate temperatures, and a stable
source of energy are also important for most
living things.

What’s the Matter?
How do Earth’s spheres interact?
• All of the five spheres of Earth interact as matter
and energy change and cycle through the system.
• A result of these interactions is that they make life
on Earth possible.

• Earth’s spheres interact as matter moves between
them. In some processes, matter moves through
several spheres.
• Earth’s spheres also interact as energy moves
from one sphere to another, and back and forth
between spheres.

• How many parts of the Earth system can you
identify in this image? How do they interact?

Balancing the Budget
What is the source of Earth’s energy?
• Almost all of Earth’s energy comes from the sun.
• A tiny fraction of Earth’s energy comes from ocean
tides and geothermal sources such as lava and
magma.

• Energy is transferred between Earth’s spheres, but
it is not created or destroyed.
• Any addition of energy to one sphere must be
balanced by an equal subtraction of energy from
another sphere.
• The movement of energy through Earth’s system
forms an energy budget.

• Trace the flow of energy through Earth’s system.

• When Earth’s energy flow is balanced, global
temperatures stay relatively stable over long
periods of time.
• Sometimes, changes in the system cause Earth’s
energy budget to become unbalanced.

What can disturb Earth’s energy
budget?
• An increase in greenhouse gases traps more
energy in the atmosphere and decreases the
amount of energy radiated out to space.
• Polar ice and glaciers reflect sunlight. When the
ice melts, the exposed water and land absorb and
then radiate more energy than the ice did.
• In each case, Earth’s atmosphere becomes
warmer, which may lead to climate changes.

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