CO- Plate tectonics. LO-Describe in writing and drawings the interactions of earths tectonic plates 1

The Theory of Plate Tectonics Earth’s crust is made of many plates These plates move as a result of convection in the mantle Earth’s surface is constantly being reshaped by these movements 2

These are the major plates that make up the lithosphere. which one do we live on? 3

What force makes the plates move? Answer: Convection cells in the mantle: ◦Convection is overturning motion resulting from heating and cooling of a substance. ◦Lithospheric plates move as a result of convection in the mantle. ◦They rotate slowly over many millions of years. ◦They rotate in different directions, thus--the plates move in different directions as well. 4

Draw a skech of this into your notes. Make sure the arrows are going the correct direction. 5

What happens when plates meet? Plate Boundaries: What happens here depends on ◦the direction each plate is moving and ◦the density of each plate Earthquakes, volcanoes, and mountain building happen at or near plate boundaries. 6

Types of Plate Boundaries Plate boundaries are classified into three groups 1.Convergent Boundary Plates moving towards each other 2.Divergent Boundary Plates moving away from each other 3.Transform Boundaries Plate sliding past one another ◦Click here for an animationClick here for an animation 7

1. Convergent Boundaries There are three types of convergent boundaries classified by the type of crust involved: ◦Continental crust to Continental crust ◦Ocean crust to Continental crust ◦Ocean crust to Ocean crust 8

The Himalayan Mountains, Including Mt. Everest formed as a result of continental- continental convergence of the Indian and Asian Plates { Mantle Continent to Continent convergent boundary 9

Island arc volcanoes and deep ocean trenches form at oceanic - oceanic convergent boundaries { Mantle Ocean to Ocean convergent boundary 10

Ocean - continental convergent boundary. Because oceanic crust is more dense than continental crust, the ocean crust is subducted beneath the continental crust. { Mantle Ocean to Continent convergent boundary 11

1. Convergent Boundaries Characteristics of a convergent boundary: Subduction Zone---which leads to the formation of: Mountains Volcanos Earthquakes 12

What is subduction? Subduction zones When two plates of different densities collide at a convergent boundary. ◦the more dense plate is driven under the less dense plate forming a subduction zone subduction zone Magma is generated in the subduction zone resulting in the formation of volcanoes. 13 { Mantle

2. Transform Boundaries Characteristics of a transform boundary: No mountains No volcanos A LOT of shallow earthquakes because the plates cause friction (earthquake). 14

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The San Andreas fault is an example of a Transform Boundary 16

3. Divergent Boundaries  Characteristics of divergent boundaries:  Mid-Ocean Ridges and Rift Valleys (large tears in the crust).  This is where Sea-floor spreading occurs.  This is where new crust is made!  Lots of small earthquakes. 17

{ Mantle 18

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New ocean crust is created at mid- ocean ridges. These are also referred to as spreading centers spreading centers This plume of dark material is called a “black smoker” Minerals Chemosynthesis Sea life – disc. 34 years ago 20

Sea-floor spreading The process that continually adds new material to the ocean floor. Evidence molten material, magnetic stripes, and drilling samples.

Evidence #1 - Molten Material The submersible, Alvin, found strange rocks shaped like pillows or like toothpaste squeezed from a tube. Such rocks can form only when molten material hardens quickly after erupting under water.

Evidence #2 - Magnetic Stripes Scientists discovered that the rock that makes up the ocean floor lies in a pattern of magnetized “stripes”. They hold a record of reversals in Earth’s magnetic field.

Evidence #3 - Drilling Samples The Glomar Challenger did a drilling sample and found that the farther away from the ridge they drilled the older the rocks were. The younger ones were in the center of the ridge.

Iceland is a volcanic island that has formed on top of a Mid- Atlantic ridge 25

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27 Draw and Color the red arrows representing the direction each plate is moving on your map handout.