Warmup 1. What geologic formation occurs where two oceanic plates are separating? (Where you have a divergent boundary) HINT: The formation at slit B from yesterday’s activity

7.1 Plate Tectonics

Layers of the Earth by composition

by physical properties Lithosphere- the outermost, rigid layer that is divided into pieces called tectonic plates Asthenosphere- the plastic layer of the mantle on which pieces of the mantle move. Mesosphere- strong, lower part of the mantle between the asthenosphere and the outer core. Outer Core- the liquid layer of the Earth’s Core Inner Core- a solid, dense center of our planet.

Continental Drift Africa & South America look like they fit together similar fossils, rocks, and glacial striations Alfred Wegner, 1915 The continents were once a super-continent called Pangea the continents are plowing through the ocean floors

Plate Tectonics Oceanic plate- thin plate with high density Earth's crust is made up of plates that ride on top of the asthenosphere The plates move due to convection currents in the mantle Oceanic plate- thin plate with high density Continental plate- thick plate with low density

Plate Boundaries Divergent plate boundary- the boundary formed from the separation of two lithospheric plates O-O: mid ocean ridge C-C: Rift Valley

Convergent plate boundary- the boundary formed from the collision of two lithospheric plates O-O: volcanic island arc O-C: volcanic arc C-C: mountains

Transform plate boundary- the boundary formed from the sliding of two lithospheric plates past each other in opposite directions

Faults Compression – the type of stress that occurs when an object is squeezed, such as when 2 tectonic plates collide. Tension- the force (stress) that occurs when forces act to stretch an object.

Folding- the bending of rock layers due to stress Two main types of folds: Anticlines- upward arching folds Synclines- downward troughlike folds

Fault- the surface along which rocks break and slide past one another. 2 Main types of faults: Normal faults- occur at divergent boundaries Reverse faults- occur at convergent boundaries