Changes Withinthe Earth
1-2
I. Physical Characteristics
A. The Earth’s Layers
1. Core – center of the earthconsisting of very hot metal(mainly iron with some nickel)
a. Inner – dense and solid
b. Outer – molten, liquid
2. Mantle – thick layer of rock (1,800miles 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, andother substances above the surface
3. Hydrosphere – water in oceans, lakes,and rivers & under ground
4. Biosphere – world of plants, animals, andother living things that occupy the planet
C. The Planet
1. 70% of earth’s surface is covered bywater
a. Atlantic Ocean
b. Pacific Ocean
c. Indian Ocean
d. Arctic Ocean
e. Southern Ocean
2. Continents – large landmasses in theoceans
a. North America
b. South America
c. Africa
d. Asia
e. Australia
f. Antarctica
g. Europe
*largest
*smallest
D. Landforms - *classified according todifferences in relief (the difference inelevation between the highest and lowestpoints)
1. mountains – high relief at least 2,000 ft.
2. hills – lower, rounded, and less steepthan mountains
3. plateaus – raised area with a generallylevel surface
4. plains – flat or gently rolling area with fewchanges in elevation
II. Physical Processes
A. Volcanoes
1. form when magma breaks through theearth’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 isdetermined by the hardness of the rockand the strength of the movement
*large, sudden movements that occuralong a fault can cause earthquakes
III. Understanding the Past
A. Plate Tectonics
1. theory that suggests the earth is not one solidsheet of rock
2. instead, it’s broken into a number of movingplates
3. the plates vary in size and thickness
4. the earth’s oceans and continents ride atopthe plates as they move in different directions
5. most earthquakes, volcanoes, & othergeological events occur on plate boundaries
B. Continental Drift
1. continental drift theory – the idea thatcontinents slowly shift their positions due tomovement of the tectonic plates on whichthey ride
2. proposed by Alfred Wegener who saidthat there once was a single“supercontinent”
3. Pangaea – the supercontinent thatbegan 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 differentcontinents
C. Seafloor Spreading
1. using sonar, scientists mapped the floorof the Atlantic Ocean and found that thefloor was not flat
2. they found mountains, deep canyons,and wide plains much like what is abovewater
3. samples that they took showed that therocks on the ocean floor were muchyounger than the rocks above water
4. seafloor spreading – molten rock fromthe mantle rises beneath the underwaterridge and breaks through a split at the topof the ridge
D. Plate Movement
1. convection – circular movement causedwhen a material is heated, expands andrises, then cools and falls
2. this happens beneath the plates andcauses them to move
E. When Plates Meet
1. Spreading – when plates move away fromeach other
*likely to have rift valley, earthquakes, &volcanic activity
2. Subduction – when one plate slidesunderneath another toward the mantle
*the rock melts & many erupt as volcanoes(Andes)
3. Converging – when two plates collide andneither sink
*buckling, folding, & faulting will produce hugemountain ranges (Himalayas)
4. Faulting – when plates slip or grind past eachother
*causes earthquakes (San Andreas Fault)
Subduction
Spreading
Converging
Faulting
F. Explaining Volcanoes
1. Ring of Fire – circle of volcanoessurrounding the Pacific Ocean
2. volcanic islands can form far away fromfault lines
3. “hot spots” are regions deep in theearth’s mantle where columns of magmarise towards the earth’s surface
a. The magma may heat underground waterand produce hot springs or geysers(Yellowstone National Park)
b. If molten rock flows out of a crack in thesurface, it may produce a volcanic islandchain (Hawaii)