Download Changes Within the Earth

Changes Within
the Earth
1-2
I. Physical Characteristics
 A.

The Earth’s Layers
1. Core – center of the earth
consisting of very hot metal
(mainly iron with some nickel)
 a.
Inner – dense and solid
 b. Outer – molten, liquid


2. Mantle – thick layer of rock (1,800
miles thick)…mostly solid
3. Crust – rocky surface layer
 B.



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Land, Air, and Water
1. Lithosphere – soil, rocks, landforms, &
other surface features
2. Atmosphere – layer of air, water, and
other substances above the surface
3. Hydrosphere – water in oceans, lakes,
and rivers & under ground
4. Biosphere – world of plants, animals, and
other living things that occupy the planet
 C.

The Planet
1. 70% of earth’s surface is covered by
water
 a.
 b.
 c.
 d.
 e.
Atlantic Ocean
Pacific Ocean
Indian Ocean
Arctic Ocean
Southern Ocean

2. Continents – large landmasses in the
oceans
 a.
North America
 b. South America
 c. Africa
 d. Asia *largest
 e. Australia *smallest
 f. Antarctica
 g. Europe
 D.
Landforms - *classified according to
differences in relief (the difference in
elevation between the highest and lowest
points)


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1. mountains – high relief at least 2,000 ft.
2. hills – lower, rounded, and less steep
than mountains
3. plateaus – raised area with a generally
level surface
4. plains – flat or gently rolling area with few
changes in elevation
II. Physical Processes
 A.


Volcanoes
1. form when magma breaks through the
earth’s crust
2. lava – molten rock
 B.




Movements in the Crust
1. fold – when rock layers bend and buckle
2. faults – breaks in the earth’s crust
*whether rock layers fold or fault is
determined by the hardness of the rock
and the strength of the movement
*large, sudden movements that occur
along a fault can cause earthquakes
III. Understanding the Past

A. Plate Tectonics




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1. theory that suggests the earth is not one solid
sheet of rock
2. instead, it’s broken into a number of moving
plates
3. the plates vary in size and thickness
4. the earth’s oceans and continents ride atop
the plates as they move in different directions
5. most earthquakes, volcanoes, & other
geological events occur on plate boundaries
 B.




Continental Drift
1. continental drift theory – the idea that
continents slowly shift their positions due to
movement of the tectonic plates on which
they ride
2. proposed by Alfred Wegener who said
that there once was a single
“supercontinent”
3. Pangaea – the supercontinent that
began to break apart 180 million years ago
4. supported his theory by finding fossils
(preserved remains of ancient animals &
plants) that were identical from all different
continents
 C.

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Seafloor Spreading
1. using sonar, scientists mapped the floor
of the Atlantic Ocean and found that the
floor was not flat
2. they found mountains, deep canyons,
and wide plains much like what is above
water
3. samples that they took showed that the
rocks on the ocean floor were much
younger than the rocks above water
4. seafloor spreading – molten rock from
the mantle rises beneath the underwater
ridge and breaks through a split at the top
of the ridge
 D.


Plate Movement
1. convection – circular movement caused
when a material is heated, expands and
rises, then cools and falls
2. this happens beneath the plates and
causes them to move

E. When Plates Meet

1. Spreading – when plates move away from
each other

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2. Subduction – when one plate slides
underneath another toward the mantle

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*the rock melts & many erupt as volcanoes
(Andes)
3. Converging – when two plates collide and
neither sink


*likely to have rift valley, earthquakes, &
volcanic activity
*buckling, folding, & faulting will produce huge
mountain ranges (Himalayas)
4. Faulting – when plates slip or grind past each
other

*causes earthquakes (San Andreas Fault)
Subduction
Spreading
Converging
Faulting
 F.



Explaining Volcanoes
1. Ring of Fire – circle of volcanoes
surrounding the Pacific Ocean
2. volcanic islands can form far away from
fault lines
3. “hot spots” are regions deep in the
earth’s mantle where columns of magma
rise towards the earth’s surface
 a.
The magma may heat underground water
and produce hot springs or geysers
(Yellowstone National Park)
 b. If molten rock flows out of a crack in the
surface, it may produce a volcanic island
chain (Hawaii)