1. Chapter 2, Section 2
“Forces of Change”

2. Earth’s Structure Surface: changes constantly
Wind, water, volcanoes, earthquakes
3 layers:
Core: inner (solid-iron and nickel) and outer (liquid-melted iron and nickel)
Mantle-releases 80% of heat generated from interior Earth
Crust-rocky shell---broken into slabs of rock (plates)---float on melted layer of upper mantle

3. Structure… Landmasses once part of Pangaea
Millions of years: broken apart---continental drift
Moving: created continents, oceans, and mountain ranges
Movement: slow (4 inches a year)
Spread apart---magma---pushed up from mantle
Bump together---forms trench
Plate tectonics---causes?
Heat rising from earth’s core-creates slow-moving currents---shifts plates around

4. Internal Forces of Change
mountains-colliding of plates
Subduction-sea plate becomes molten material---becomes magma-forms volcanic mountains
Accretion---movement levels off seamounts---piles up debris in trenches
Spreading---allows magma from within earth to come between plates-builds undersea volcanoes
Folds-
Faults-San Andreas Fault (CA)---folded land cannot be bent any further---crust cracks/breaks

5. San Andreas Fault

6. Earthquakes Sudden, violent movements of plates along fault line
Shaking changes surface
Occur where different plates meet one another
Tension builds up---stain becomes too intense---rocks snap and shift---ground trembles
Cities along Ring of Fire---zone of earthquake and volcanic activity surrounding Pacific Ocean

7. Ring of Fire---compare to pg. 39

8. Volcanic Eruptions
Mountains formed by lava or magma that breaks through earth’s crust
Rise along plate boundaries
Rocky plate-melts as it goes into hot mantle
Molten rock too thick-flow is blocked-pressure builds
Some areas are hotter than others----hot spots may create geysers or hot springs (Old Faithful)

9. Yellowstone National Park--- Old Faithful

10. External Forces of Change
Weathering
*physical---when large landmasses of rock are physically broken down
*chemical---changes chemical makeup of rocks
2. Wind Erosion
*involves movement of dust, sand, and soil
*plants help protect land
*Great Plains s

11. External… 3. Glacial erosion *form over long periods of time
*weight causes movement-pick up rock and soil
*change landscape
*melt-leave behind moraines
*two types: 1-sheet 2-mountain
4. Water Erosion
*fast-moving water-greatest cause of erosion
*begins when water flows off land downhill in streams
*oceans---waves pound cliffs, etc