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Module E: Unit 1, Lesson 1 – Earth’s Spheres
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.
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 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.
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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.
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.
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.
• 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.