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CHAPTER 2: THE EARTH
The Earth’s Spheres

Hydrosphere - part of the Earth made up of oceans, lakes, rivers, and other
water bodies. About

70% of the Earth’s surface is water
Lithosphere - part of the Earth made up of land, including ocean basins. About
30% of the Earth’s surface is land.


Atmosphere - gases that cover the Earth and make up the air we breathe.
Biosphere - part of the Earth that supports life (plants, animals, and humans).
Landforms
~ Landforms are the natural or
physical features of the Earth’s surface and have a
particular shape or elevation.
1.
Four major types of landforms
a.
Mountains
b.
Hills
c.
Plains
d.
Plateaus
2. The Earth’s most visible landforms are the large landmasses called
a.
Africa
b.
Antarctica
c.
Asia
d.
Australia
e.
Europe
f.
North America
g.
South America
continents.
Earth’s Heights and Depths
1.
Mt. Everest - the Earth’s highest point located in Southwest Asia; its elevation is
about
2.
29,035 feet above sea level.
Dead Sea Shore - the Earth’s lowest point of dry land; it is about 1,349 feet
below sea level.
3.
Mariana Trench - the Earth’s deepest known depression; it is 35,827
feet
deep (below sea level).
Earth’s Structure
˜ The Earth’s surface is in
slow but constant motion.
˜ Some forces that change the Earth occur at the
surface, such as wind and water.
˜ Some forces that change the Earth originate (start) deep within the Earth’s interior, such
as
earthquakes and volcanic eruptions.
A Layered Planet
1.
Core
a. Inner core - super hot, nickel and iron under great pressure
b. Outer core - super hot, liquid nickel
2.
Mantle - surrounds the core, thick layer of hot dense rock
3.
Crust - thin rocky shell that covers the mantle; it is broken into slabs called plates,
that hold and carry the Earth’s oceans and continents
Plate Movement
1.
Continental drift - theory of a “super continent” - Pangaea, which broke apart
2.
Plate tectonics, or the movement of plates, is usually gradual; but, can change
the face of the Earth.
a. Plate tectonics can include plates crashing together, pulling apart, or sliding and
grinding into one another
b. Plate tectonics can create mountains, volcanoes, and earthquakes.
Internal Forces of Change
Folds and Faults
1.
Folds are bends in layers of rock formed as moving plates squeeze the Earth’s
surface.
2.
Faults, or cracks in the Earth’s surface, are formed as plates grind against or
slide past one another. The grinding of the two plates causes tremors.
Earthquakes
1. Earthquakes are sudden,
a. The
violent movements of plates along a fault line.
Ring of Fire is an area of high volcanic and earthquake activity along
the Pacific Rim.
Volcanic Eruptions
1. Volcanoes are mountains formed by lava or by
magma that breaks through the
Earth’s crust.
a. Volcanoes often form plate boundaries where one plate plunges below
another. The rocky plate melts as it dives downward into the hot mantle.
b. Volcanoes also arise in various hot spots, where deep within the Earth the
temperature is hotter than normal. The
Hawaiian Islands were formed by
this type of volcanic activity.
c. Molten rock may also heat underground water to create
geysers or hot
springs, like those found in Yellowstone National Park in Wyoming.
External Forces of Change
A.
Weathering - the process that breaks down rocks
B.
Erosion - the process that wears away the Earth’s surface
1. The movement of dust, sand, and soil from one place to another is called
wind erosion.
2.
Glacial erosion is the wearing away of the Earth by large bodies of ice
that move slowly across the Earth’s surface. As they move they carry
along rock and soil.
3.
Water erosion is the wearing away of the Earth’s surface by moving
water
C.
Deposition - the process of adding land or sediment to an area by moving
water, wind or ice
The Water Cycle
~ The
hydrosphere is the part of the Earth’s surface covered by water including
oceans, lakes, rivers, and other water bodies.
~ About
97% of the Earth’s water is saltwater
~ About
3% of the Earth’s water is freshwater, but about 2% of it is frozen
* The total amount of water on the surface of the earth is unchanging, but the water is in
constant motion
The
hydrologic/water cycle is the regular movement of the Earth’s water.
1.
The Sun’s heat causes water in the oceans to
evaporate, or to change from a
liquid to a gas. The water vapor gathers in the air and rises with the warm air.
2.
of
As the air cools, water vapor changes back to a liquid through the process
condensation.
3.
When clouds gather more water than they can hold, they release the moisture.
Water released from the clouds, in the form of rain, snow, or sleet is called
precipitation.
4.
Precipitation returns to the Earth. It sinks into the ground through
or, as
runoff, it returns to the Earth’s water bodies.
infiltration;
*The amount of water that evaporates is approximately the same as the amount that falls
back to the Earth. The total volume of water in the Earth’s water cycle is
geographers believe this is still true?
constant.
Do
Bodies of Saltwater
A. Oceans
1. About
97% of the Earth’s water is salt water.
Most of the Earth’s water is
contained in one of the five large water bodies, called the
a.
Atlantic
b.
Arctic
c.
Indian
d.
Pacific
e.
Southern
oceans.
B. Ocean Water to Drinking Water
1. Although
97% of the world’s water is found in oceans, it is too salty to drink or
use for irrigation and manufacturing.
2. Scientists are developing ways to remove the salt from sea water. The process,
known as
desalination, is still in the early stages of development.
Bodies of Freshwater
~ About
3% of the Earth’s total water supply is freshwater.
~ More than
2% of the Earth’s freshwater is frozen in glaciers and polar ice caps.
Groundwater
1.
Groundwater is fresh water found beneath the Earth’s surface.
2. This type of freshwater comes from rain and snow that has filtered through the
soil and rock and accumulated below the Earth’s surface. Some water from lakes and
rivers may also become part of the groundwater.
3. People often dig wells and use springs that tap into this type of freshwater.
4. An
aquifer is a layer of porous rock below that Earth’s surface that traps and
holds groundwater.
5.
Aquifers and groundwater are important sources of freshwater.