Plate Tectonics A. Layers of Earth 1.Each have different densities 2.Composition is determined by earthquake waves and meteorites 3.Layers: a)Lithosphere – includes crust and ridged mantle b)Asthenosphere – plastic mantle, not quite solid c)Mantle – stiffer mantle d)Outer core – liquid e)Inner core – solid

4.Continental crust a)Granitic composition b)thicker and less dense than ocean crust 5.Oceanic crust a)Basaltic composition b)Thinner and more dense than continental crust 4.Pressure, temperature and density ALL increase with depth

B. Plate movements 1.Evidence of movement 1.Pangaea – supercontinent 2.Shape of coastlines – fit together like a puzzle 3.Fossil correlation – rare fossils match across ocean basins 4.Rock correlation – rocks match on the coastlines, across ocean basins 5.Climate changes – coal found in Antarctica, glacial striations found in Australia and Africa. 1. Caused by convection currents with Earth (differences in density)

Divergent boundaries

2.Divergent boundary a)Occurs where two plates are moving apart b)Water fills low areas as plates separate c)Lava begins forming rock d)mid-ocean ridges form e)Youngest rocks are at “spreading centers” – still being formed there f)Magnetic orientation changes (normal and reverse)

Collision Plate: Continental plate collides with another continental plate

3.Convergent Plate boundaries a)Where two plate move toward each other b)Two types 1.Collision – two continental plate collide 2.Subduction – when one plate moves under the other (subducted) - ocean / ocean plate (or) - ocean / continental plate 4.Collision Plate – two continental plates collide a)Crust moves upward – mountain building b)Appalachian Mountains

Ocean / Continental Plate Ocean / Ocean Plate

5.Subduction boundaries a)Ocean Plate / Continental Plate 1.Ocean plate is subducted under the continental plate (thinner, less dense) 2.formation of deep sea trenches 3.Bordered by a volcanic mountain chain on the continental plate 4.Ex: Mt. St. Helens, WA 5.Evidence - Uplift of fossils

b. Ocean Plate / Ocean Plate 1.One ocean plate is subducted 2.formation of deep sea trenches 3.Bordered by volcanic islands 4.Ex: Eastern Caribbean islands 5.Evidence – Subsidence of fossils (shallow Fish fossils found deep in ocean floor)

6. Transform Boundaries a)two plates slide past each other b)Major earthquakes c)Ex: San Andres Fault 7. Hot Spots a)Magma comes up through crust b)Volcanic islands form c)Ex: Hawaii

Earthquakes -shaking of the ground -Release of energy -Major cause - movement of plates -Focus - where the earthquake takes place underground -Epicenter - on the surface directly above the focus A. General Information:

B.Earthquake waves 1)P-waves - primary (compression) waves - travel back and forth - travel fastest - can go through any material 2) S-waves - secondary (shear) waves - travel perpendicular - half the speed of P waves - can NOT go through liquids

C) Earth’s Interior 1)Earthquake waves along with meteorites help to infer the composition and density interior of Earth 2)Earthquake waves refract (bend) and sometimes are absorbed 3)S-waves cannot travel through the liquid outer core 4)Shadow zone - an area where no waves are present due to bending

D)Locating an epicenter 1) minimum of three seismograph stations are needed 2) one station gives distance only 3) draw three circles - where they all intersect is where the epicenter is located 4) closest location - smallest circle - shortest difference in arrival time - first P-wave to get to station