1. Changes Within the Earth 1-2

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

3.  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

4.  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

5.  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

6.  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

7. II. Physical Processes  A. Volcanoes  1. form when magma breaks through the earth’s crust  2. lava – molten rock

8.  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

9. 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

11.  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

13.  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

15.  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

16.  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)

17. Subduction Spreading Converging Faulting

18.  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)