Chapter 2: The Earth
Ch.2:The Earth
Sec 1: Planet Earth
Our Solar System
Planets: M.V.E.M.J.S.U.N.
Space Matter:
o Asteroids– small, irregularly shaped planet like objects.
Found in the asteroid belt in between the orbits of Mars &
Jupiter.
o Comets– Composed of ice dust particles & frozen gases,
look like bright balls of light w/ long feathery tales.
o Meteoroids– pieces of space debris- chunks of rock &
iron. Usually burned up in Earth’s atmosphere.
Ch.2:The Earth
Sec 1: Planet Earth
Ch.2:The Earth
Sec 1: Planet Earth
Getting to Know Earth
About 70 % of Earth’s surface is made up of water. Oceans, lakes, rivers,
& other bodies of water make up the Earth’s Hydrosphere.
30% of the Earth’s surface is land, this includes continents & islands. This
land is known as the Lithosphere.
The air we breathe is apart of Earth’s Atmosphere, a layer of gases
extending 1,000 miles above Earth’s surface. Our atmosphere is
composed of 78% Nitrogen, 21% Oxygen & 1% other gases.
The part of Earth that supports life is the Biosphere.
Ch.2:The Earth
Sec 2: Forces of Change
Earth’s Structure
o The Earth is composed of 3 layers. The core (inner & outer),
mantle, & the crust.
o At the center of the planet is a super hot, solid inner core.
4,000 miles below the Earth’s surface.
o Surrounding the inner core is a liquid outer core. This is a liquid
band of nickel & iron. This section begins at 1,800 miles below
Earth’s surface.
o The layer that contains thick, dense rock is know as the Mantle.
Consists of silicon, aluminum, iron, magnesium, oxygen & other
elements. This mixture continually rises, cools, sinks, warms up,
& rises again.
Ch.2:The Earth
Sec 2: Forces of Change
Inside the Earth
Ch.2:The Earth
Sec 2: Forces of Change
Plate Movement
At one point in time, millions of years ago, the
continents of the Earth formed what was
known as Pangaea. Over millions of years,
this “super-continent” has broken apart into
small continents. The theory that the
continents were once joined then slowly
drifted apart is known as Continental Drift.
Ch.2:The Earth
Sec 2: Forces of Change
Ch.2:The Earth
Sec 2: Forces of Change
More about plates . . .
o When the plates spread apart, Magma, molten
rock, is pushed up from the mantle & ridges
are formed.
o Plate Tectonics refers to all these movements
which create many of the Earth’s physical
features. Majority of the time these movements
are gradual at only 4 inches a year (we can’t
feel this movement).
Ch.2:The Earth
Sec 2: Forces of Change
Plates & Plate Movement
Ch.2:The Earth
Sec 2: Forces of Change
Colliding & Spreading Plates
. Subduction- Mountains are created when a
sea plate collides with a continental plate.
Ch.2:The Earth
Sec 2: Forces of Change
o Accretion- pieces of Earth’s crust come
together slowly as the sea plate slides under
the continental plate.
Ch.2:The Earth
Sec 2: Forces of Change
Colliding & Spreading Plates . . .cont.
o New land is created when two sea plates
converge. This happens when one plates moves
under another, forming island chains at the
boundary. Sea plates can also pull apart in a
process known as Spreading.
o The resulting deep crack allows magma from
within the Earth to well up between plates. This
magma hardens to build undersea volcanic
mountains or ridges. This occurs down the middle
of the Atlantic Ocean’s floor, pushing Europe and
North America away from each other.
Ch.2:The Earth
Sec 2: Forces of Change
Ch.2:The Earth
Sec 2: Forces of Change
Folds and Faults
Folds: Moving plates sometimes squeeze the
Earth’s surface until it folds or bends, in
layers of rock.
Fault :Plates also grind or slide past each
other, this creates cracks in the Earth’s
crust. World’s most famous fault is San
Andreas Fault, in California.
Ch.2:The Earth
Sec 2: Forces of Change
Ch.2:The Earth
Sec 2: Forces of Change
Earthquakes
o Earth quakes: Sudden, violent movements of plates along
a fault line. Tension builds up along fault lines as the plates
stick. The strain eventually becomes so intense that the
rocks suddenly snap and shift. This movement releases
stored-up energy along the fault.
o The Ring Of Fire is one of the most earthquake prone
areas on the planet. The cities of Kobe (Japan), San
Francisco and Los Angeles are located here. This is a
zone of earthquake and volcanic activity surrounding the
Pacific Ocean. It marks the boundary where the plates that
cradle the Pacific meet the plates that hold the continents
surrounding the Pacific.
Ch.2:The Earth
Sec 2: Forces of Change
o External forces such as wind and water also
change the Earth’s surface. Wind and water
movements involve 2 processes:
Weathering and erosion.
o Weathering: The process that breaks down
rocks on Earth’s surface into smaller pieces.
o Erosion: The wearing away of Earth’s
surface by wind, glaciers and moving water.
Ch.2:The Earth
Sec 2: Forces of Change
Weathering
Physical weathering: When large masses of rock
are physically broken down into smaller pieces.
Ex: water seeps into the cracks of a rock, freezes,
then expands, and causes the rock to split.
Chemical Weathering: Changes the chemical
makeup of a rock. Transforming its minerals or
combining them with new elements. Ex: water
mixed with Carbon Dioxide from the air easily
dissolves certain rocks, such as limestone.
Ch.2:The Earth
Sec 2: Forces of Change
Ch.2:The Earth
Sec 2: Forces of Change
Wind and Glacier
Erosion
o The Chinese
Yellow River Basin
:is thickly covered
with loess, a fertile,
yellow-gray soil
deposited by the
wind. This is a type
of wind erosion.
o Glaciers can also
cause weathering.
When glaciers melt
and recede, in some
places they leave
behind large piles of
rocks and debris
known as Moraines.
Ch.2:The Earth
Sec 3: Earth’s Water
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The Water Cycle
The total amount of water on Earth doesn’t change,
however, the Earth’s water is constantly moving– from the
oceans to the air, to the ground and finally back to the
oceans, this is known as the Water Cycle.
The sun drives the cycle by evaporating water from
Earth’s surface. Evaporation is the changing of liquid
water into vapor or gas.
When warm air cools, it cannot retain all of its water vapor,
so the excess water vapor changes into liquid water, this
process is called Condensation.
Tiny droplets of water come together to form clouds. When
the clouds gather move water than they can hold, they
release moisture, which falls to the Earth as Precipitation–
rain, snow, sleet, hail.
Ch.2:The Earth
Sec 3: Earth’s Water
Ch.2:The Earth
Sec 3: Earth’s Water
Bodies of Salt Water
o Oceans– About 97 % of the Earth’s water
consists of water that circles the planet, our 4
oceans: the Pacific, Atlantic, Indian, and Arctic.
o Seas, Gulfs, & Bays—are bodies of water that
are smaller than oceans and are often enclosed by
land.
o Desalination: The process in which we remove
the salt from ocean water and use it as a supply of
freshwater, is very expensive, and is still in the
early stages of development
Ch.2:The Earth
Sec 3: Earth’s Water
Bodies of Freshwater
o Only 3% of the Earth’s total water supply is freshwater. 2%
of Earth’s total water supply is frozen in glaciers and
icecaps. Lakes, rivers, & streams also account for Earth’s
small supply of freshwater.
o Groundwater– which is freshwater that lies beneath the
Earth’s surface, comes from rain & melted snow that filters
through the soil & from water that seeps into the ground
from rivers & lakes. Wells & springs tap into the
groundwater & are important sources of freshwater for
people.
o Aquifer :An underground porous rock layer often saturated
with water in the form of streams