1.3 Outline1.3 Outline

Plates Move ApartPlates Move Apart

I. Tectonic Plates Have Different I. Tectonic Plates Have Different BoundariesBoundaries

1)1) Divergent boundary:Divergent boundary: occurs occurs where plates move apart; mainlywhere plates move apart; mainly found in oceanfound in ocean

2)2) Convergent boundary:Convergent boundary: occurs occurs where plate push togetherwhere plate push together

3)3) Transform boundary:Transform boundary: occurs occurs where plates scrape past each where plates scrape past each otherother

II. The sea floor spreads apart at divergent II. The sea floor spreads apart at divergent boundariesboundaries

1)1) Rift valley:Rift valley: gap that forms as a result gap that forms as a result of mid-ocean ridges expandingof mid-ocean ridges expanding

A.A. Mid Ocean Ridges and Rift ValleysMid Ocean Ridges and Rift Valleys1)1) Mid-ocean ridgesMid-ocean ridges, , rift valleysrift valleys and and new crustnew crust

mark where the sea floor spreads apartmark where the sea floor spreads apart2)2) When molten material rises from the When molten material rises from the

asthenosphereasthenosphere, cold ocean water cools the , cold ocean water cools the rock until rock until it becomes solidit becomes solid

3)3) As the plates move As the plates move apartapart, new , new crackscracks open open in the solid rockin the solid rock

III. Continents split apart at divergent III. Continents split apart at divergent boundariesboundaries

1)1) Like the sea floor, Like the sea floor, continentscontinents also also spread apart at a spread apart at a divergentdivergent boundaryboundary

2)2) Begins to form when Begins to form when hot material hot material risesrises from deep in the from deep in the mantlemantle causing the crust to causing the crust to bulge upwardbulge upward

3)3) Crust cracks as it is stretched, Crust cracks as it is stretched, causing a causing a rift valley to formrift valley to form

III. Continents split apart at divergent III. Continents split apart at divergent boundaries (cont.)boundaries (cont.)

4)4) Volcanoes form from Volcanoes form from magma rising magma rising through the cracked, thinned crustthrough the cracked, thinned crust

5)5) Thinned valley floor sinks lower Thinned valley floor sinks lower until it is until it is below sea levelbelow sea level

6)6) Water from nearby oceans or rivers Water from nearby oceans or rivers may may fill the valley and form a sea or fill the valley and form a sea or lakelake

IV. Hot spots can be used to track plate IV. Hot spots can be used to track plate movementsmovements

1)1) Hot spots:Hot spots: an area where heated an area where heated rock rises to thin columns (plumes) rock rises to thin columns (plumes) from the mantlefrom the mantle

a)a) Offer a way to measure Offer a way to measure plate plate movementmovement, because a , because a hot spot hot spot generally stays in one place, while generally stays in one place, while tectonic plate above it keeps movingtectonic plate above it keeps moving