Chapter 2, Section 2 “Forces of Change”

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

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

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

San Andreas Fault

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

Ring of Fire---compare to pg. 39

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)

Yellowstone National Park--- Old Faithful

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---1930s

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