Bell Ringer Take out a sheet of paper, put your name on it. Write your answer to the questions. 1.What type of tectonic activity made Hawaii? 2.What activity within the mantle causes plate movement? 3.What type of erosion created the Great Lakes? 4.What type of plate boundary is the San Andreas fault in California. 5.What type of external force of change carries away pieces of rock and creates sediment?
Earth is composed of 3 layers: 1.Core 2.Mantle 3.Crust
1.Core (inner & outer) – made of iron & nickel a. inner – super hot solid -about 4,000 mi. below surface of earth b. outer – super hot liquid -about 1,800 mi. below the surface of earth -temperatures can reach 8,000*F
2.Mantle -hot, dense mostly liquid rock -pockets of magma (rise & fall) -made of silicon, aluminum, iron, magnesium, and oxygen
3.Crust -rocky shell which forms earth’s surface -broken into more than a dozen slabs of rock called plates that rest on layer of the upper mantle -these plates carry earth’s oceans & continents
-Continental Drift : theory that continents were once joined and then slowly drifted apart *super-continent was called Pangaea
PANGEA
-Plate Tectonics – term scientists use to describe the activities of continental drift and magma flow which create many of Earth’s physical features *plates crash into each other, pull apart, or grind and slide past each other (about 4 inches or less per year)
-Why do plates move? -convection currents *hotter material is less dense & rises (toward crust of Earth) *cooler material is more dense & sinks (toward core of Earth) *creates continuous circular motion/movement
Why might a scientist want to study plate tectonics?
Divergent Boundary -Plates move apart (rift) from each other (tension) 1. Continental-Continental = creates gap (rift valley) in which water can flow in *ex: Red Sea; Great Rift Valley
2.Oceanic-Oceanic = magma rises up & creates new crust on edges of the 2 plates -enlarges the ocean floor & forms underwater mountain ranges called ocean ridges *example: Mid-Atlantic Ridge – North American plate & Eurasian & African plates pulling apart
Convergent Boundary In general: -Plates move toward each other & collide (compression) -One plate is forced below the other (subduction)
1.Oceanic-Continental -subduction occurs = heavier sea plate dives beneath lighter continental plate *sea plate begins to melt into magma pressure builds magma bursts thru crust to form volcanic mtns *ex: Andes Mountains in S. America – collision of Nazca and SA plates
2.Oceanic- Oceanic -subduction occurs *sea plate begins to melt & magma rises to ocean surface in form of volcanic islands *example: Philippine islands- collision of Philippine & Pacific plates
3.Continental- Continental -pressure builds until one plate is subducted *sometimes sinking plate melts & rises as volcanic mountains are formed *example: Himalaya mountains (South Asia) – collision of Indian & Eurasian plate
Transform Boundary -Plates slide past each other along faults (cracks in the earth’s crust) - Crust is pulled and stretched (tension) until tension is released (Earthquake)
-example: San Andreas Fault in California
HOT SPOTS -Magma rises thru the tectonic plate -The magma erupts on the surface as lava & hardens to form volcanic islands -Magma continues to rise from the hot spot, building up an undersea volcano that will one day become an island -a chain is formed
Animations Hot Spot Animation
Guess the Tectonic Activity!
Oceanic-Oceanic Convergent
Oceanic-Oceanic Divergent
Transform
Continental-Continental Convergent
Continental-Continental Divergent
Oceanic-Continental Convergent