Presentation on theme: "Plate Tectonics. Plate Tectonics What is Plate Tectonics The Earth’s crust and upper mantle are broken into sections called plates Plates move around."— Presentation transcript:
12 Convection CurrentsPlates move by the transfer of heat through heated material.Hot magma in the Earth moves toward the surface, cools, then sinks again.Creates convection currents beneath the plates that cause the plates to move.
23 2. Transform Fault Boundaries Boundary between two plates that are sliding past each otherMoving in opposite directionsMoving in same directions at different speedsEARTHQUAKES along faultsEx: San Andreas fault in CA
26 3. Convergent Boundaries Boundaries between two plates that are colliding There are 3 types…
27 Type 1 Ocean plate colliding with a less dense continental plate Subduction Zone: where the more dense plate slides under the less dense plateVOLCANOES occur at subduction zonesEarthquakes are common
36 Questions... What are the three types of boundaries? What direction do plates go for each?Which boundary has a subduction zone…what occurs at a subduction zone?
37 Alfred WegenerIn 1915, German geologist Dr. Alfred Wegener proposed an idea called the Theory of Continental Drift.Said all continents were joined together about 250 million years ago as a supercontinent Pangea (“all land”).Eventually Pangea split and moved into current positions
38 Wegner’s Clues or Evidence….. Shape of the continents –They seem to fit together as one big puzzle….
40 Clues or Evidence continued… Climate (Glacial Deposits)..
41 Clues or Evidence continued… Rocks - similar mountain ranges found on different continents separated by oceans…
42 EvidenceA system of underwater mountain chains or mid-ocean ridges, rise thousands of meters above ocean floorCaused by plate movement called sea-floor spreading at a divergent boundaryYoungest ocean floor rocks – near mid ocean ridgesOldest near the edge of the continentsWhen the sea floor reaches a continental boundary, it is forced downward beneath the continental, called a sea floor trench