Chapter 2: Earth’s Structure
Lesson 1: Spherical Earth
Describing Earth
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Earth is shaped like a ball, with all points
on the surface at an equal distance from
the center.
Earth is somewhat flattened at the poles
with a slight bulge around the equator.
This means the diameter of Earth is larger
around the equator than at the poles.
Earth has an average diameter of almost
13,000km.
Earth System
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The Earth system has four main spheres:
the atmosphere, hydrosphere, geosphere,
and biosphere.
As major source of energy for Earth
processes, the sun can be considered part
of the system as well.
Earth Systems Overview
The Earth is a system consisting of four
major interacting components:
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the atmosphere,
• the biosphere,
• the hydrosphere, and
• the geosphere
Let’s examine each of these four
spheres in detail………
The Atmosphere
The Earth is surrounded by a blanket
of air, which we call the atmosphere.
• The atmosphere consists of four
unique layers (the troposphere, the
stratosphere, the mesosphere, and
the thermosphere).
• The atmosphere reaches over 350
miles up from the surface of the
Earth.
• The atmosphere is primarily
composed of nitrogen (about 78%)
and oxygen (about 21%). Other
components exist in small quantities.
The Biosphere
The biosphere is the “life zone” of the Earth, and
includes all living organisms (including humans), and all
organic matter that has not yet decomposed.
• The biosphere is structured into a hierarchy known as a
food chain.
• Energy and nutrients, like carbon, are transferred from
one level of the food chain to the next.
Hydrosphere
The hydrosphere contains all the water
found on our planet.
• Surface Water: Includes the ocean as well
as water from lakes, rivers and creeks.
• Ground Water: Includes water trapped in
the soil and groundwater.
• Atmosphere: water vapor.
• Frozen water: Includes ice caps and
glaciers. Specifically called the cryosphere.
• Only about 3% of the water on Earth is
“fresh” water, and about 70% of the fresh
water is frozen in the form of glacial ice.
(0.9% in liquid form)
Geosphere
The geosphere is the solid
part of the earth, from the
core to the surface.
• Includes volcanoes, rocks,
minerals, coal, oil etc.
•Mineral resources are mined
from the geosphere.
Forces that change Earth
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Lands are constantly being created and
destroyed by competing forces.
Constructive and destructive forces
Earth System Science
Earth System Science
is the study of how the
four spheres of the Earth
system interact
continually, each
affecting the others.
Example: A scientist
that studies global
warming is an Earth
System Scientist.
System Interactions
constructive force
Volcanoes (geosphere) erupt,
sending ash and gases into the
air (atmosphere) and sending
lava and ash down onto
surrounding forests (biosphere)
and human habitations
(biosphere).
Geosphere
Atmosphere
Biosphere
System Interactions
destructive force
Hurricanes (atmosphere) sweep
across the ocean (hydrosphere)
and onto the land (geosphere),
damaging the dwellings of people
(biosphere) who live along the
coast.
Hydrosphere
Atmosphere
Geosphere
Biosphere
System Interactions
destructive force
Earthquakes (geosphere) can damage
buildings which may kill people (biosphere),
as well as cause fires which release gases
into the air (atmosphere). Earthquakes in
the ocean may cause a tsunami
(hydrosphere) which can eventually hit land
and kill both animals and people
(biosphere).
Biosphere
Geosphere
Atmosphere
Hydrosphere
How did Earth Form
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1.
Earth forms about 4.6 billion years ago.
Materials from a large cloud of gas, ice,
and dust came together through gravity.
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2.
Gravity is the force of attraction between every
object because of their masses.
This cloud is called the nebula. The
nebula shrinks and flattened into a disk
denser in the center, forming the Sun.
3.
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Next the planets began to take shape
from the remaining of the material.
Earth formed as gravity pulled these
small particles together and became
bigger in size.
Earth generated thermal energy (heat) in
its interior, gravity pulled the surface
together and form a relatively even
spherical surface.
Thermal energy melt some of these
materials and form different layers
according to their masses.
Density
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Density is the amount of mass in a
material per unit volume.
D= m/V
D= density
m= mass
V= volume