Changes Within the Earth1-2

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. 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. Atlantic Ocean b. Pacific Ocean c. Indian Ocean d. Arctic Ocean e. Southern Ocean

2. Continents – large landmasses in the oceans a. North America b. South America c. Africa d. Asia e. Australia f. Antarctica g. Europe

*largest

*smallest

D. Landforms - *classified according to differences in relief (the difference in elevation between the highest and lowest points) 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

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. 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 *likely to have rift valley, earthquakes, & volcanic

activity 2. Subduction – when one plate slides

underneath another toward the mantle *the rock melts & many erupt as volcanoes

(Andes) 3. Converging – when two plates collide and

neither sink *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)