PLATES AND TECTONIC MOVEMENT

There are 7 major and 15 minor plates worldwide

Causes of Plate Motion (3 Causes)  Mantle Convection Hot mantle material rises, cools, and sinks Unequal distribution of heat within Earth causes thermal convection ******Convection occurring in the mantle is a possible driving force for plate movement.******

Causes of Plate Motion Slab-pull: cool, dense oceanic crust sinks into mantle and “pulls” the trailing lithosphere along. (MOST IMPORTANT!!) Ridge-push causes oceanic lithosphere to slide down the sides of the oceanic ridge under the pull of gravity. (less important than Slab-pull)

Types of Plate Boundaries  Divergent boundaries (also called spreading centers) - two plates move apart.  Convergent boundaries - two plates move together.  Transform fault boundaries - two plates grind past each other (without the production or destruction of the lithosphere).

Creates RIFT VALLEYS and MID-OCEAN RIDGES DIVERGENT BOUNDARY Creates RIFT VALLEYS and MID-OCEAN RIDGES

Creates VOLCANOES, TRENCHES, ISLAND ARCS and MOUNTAINS CONVERGENT BOUNDARIES Subduction Zone 2 types! Creates VOLCANOES, TRENCHES, ISLAND ARCS and MOUNTAINS

TRANSFORM BOUNDARY Video Movements along transform boundaries are felt as Earthquakes

Evidence for Plate Tectonics 1) Paleomagnetism - natural remnant magnetism in rocks; Shows Earth’s magnetic field as it existed in the past.

2) Earthquake Patterns 3) Ocean Drilling Link between deep-focus earthquakes and ocean trenches. Absence of deep-focus quakes along oceanic ridge was consistent with the new theory. 3) Ocean Drilling Ages of seafloor sediment confirmed what seafloor spreading hypothesis predicted. Youngest oceanic crust is at the ridge crest; oldest at continental margins.

4) Hot Spots Hot spot (mantle plumes) Definition: Concentration of heat in mantle capable of producing magma, which rises to Earth’s surface Hot spot evidence supports that the plates move over the Earth’s surface. (Hot spots hold still, and plates move) Ex: Pacific plate moves over a hot spot, producing the Hawaiian Islands.

Hot Spot

What is the type of plate boundary where two plates move together, causing one of the slabs of lithosphere to descend into the mantle beneath the overriding plate? Oceanic- continental convergent Divergent Transform fault Continental - continental convergent

What are the following type of plate boundaries? C Divergent Convergent Transform Convection Cells