Plate Tectonics Earth Science 1 What is Plate

Plate Tectonics Earth Science 1

What is Plate Tectonics? l Modern theory used to explain how Earth’s physical features (geology and geography) have formed. 2

Layers of the Earth 3

Layers of the Earth l l Lithosphere: crust and upper part of mantle Asthenosphere: mantle beneath lithosphere 4

Layers of the Earth l l Crust: Thin rock layer; forms oceanic and continental plates Mantle: Molten rock layer; flows slowly and smoothly 5

Layers of the Earth l Earth’s lithosphere is made of several plates that move because of convection currents in the asthenosphere. 6

Earth’s Plates 7

History of Plate Tectonics l In 1915, German geologist Dr. Alfred Wegener proposed an idea called the Theory of Continental Drift. 8

History of Plate Tectonics l He believed all continents were joined together about 250 million years ago as a megacontinent Pangaea (“all land”). 9

History of Plate Tectonics l He also believed all of Earth’s water was one large ocean called Panthalassa (“all sea”). 10

History of Plate Tectonics l Most of Wegener’s ideas were rejected because he could not explain why Pangaea split apart. 11

History of Plate Tectonics l New evidence to support Wegener’s idea was discovered in the 1960 s, leading to the development of the modern Theory of Plate Tectonics. 12

Supporting Evidence l Continental Shelf Fit l Continents appear to fit together like puzzle pieces 13

Supporting Evidence l l Paleoclimate Glacier patterns indicate Pangaea existed near the South 14

Supporting Evidence l Fossils l Similar fossils are found in both South America and Africa. 15

Supporting Evidence l Rocks l Mountain ranges appear to extend across continents. 16

Supporting Evidence l l l Climate Change Salts and coal – form in warm climate can be found up north (Michigan was once near the equator) Coral deposits, limestone – found in Grand Canyon and Canada – these were once in warm climates 17

Supporting Evidence l Paleomagnetism l Magnetic patterns in rocks indicate continental shift. 18

Supporting Evidence l l Seafloor Spreading Ocean crust is younger than continental crust. 19

Supporting Evidence l Earthquake Patterns l Most earthquakes occur along plate boundaries. 20

Supporting Evidence l l Volcanic Hot Spots Rising plumes of mantle create volcanic chains that mark plate movement. 21

Plate Boundary Interactions l Divergent Boundary: Plates move apart as magma rises to surface Forms ridges, rises, and rifts 22

Plate Boundary Interactions 23

Plate Boundary Interactions l Convergent Boundary: (3) Plates collide creating subduction zones (areas where crust is forced into the asthenosphere and melted) 24

Plate Boundary Interactions l Ocean-Continent Convergence: l Subduction of ocean crust l Forms volcanic mountains 25

Plate Boundary Interactions 26

Plate Boundary Interactions l Ocean-Ocean Convergence: l Subduction of oceanic crust l Forms island arcs and trenches 27

Ocean – ocean convergence 28

Plate Boundary Interactions l Continental Convergence: l Form mountain ranges 29

Plate Boundary Interactions l Transform Fault Systems: l Plates slide past each other creating fault zones l Causes earthquakes 30

Plate Boundary Interactions 31

Why does NE quake? l l l Intraplate earthquakes "ancient zones of weakness" are being reactivated in the present-day stress field. https: //www 2. bc. edu/~ kafka/Why_Quakes/w hy_quakes. html 32