What is the Rock Cycle? • The process where the 3 types of rocks change, form new rock, and are recycled
Volcanic Activity Volcanoes erupt and lava cools and hardens into intrusive or extrusive igneous rock.
Weathering and Erosion • Over long periods of time, large rocks are worn down to small particles called sediments (sand, pebbles, etc). • Water, wind and ice can break rocks down. • Rocks can also be broken down so much that they become dissolved in water (they can even be used by living organisms)
Deposition • As rivers get deeper or flow into the ocean, their current slows down, and the rock particles (mixed with soil) sink and become a layer of sediment. Often the sediment builds up faster than it can be washed away, creating islands or sandbanks
Compaction and Cementation • The layers of sediments stack up. • Dissolved minerals fill in the gaps between the sediments and then get solid like cement. • After years, the sediments turn into sedimentary rock!
Metamorphism • Over really long periods of time, sedimentary or igneous rocks can get buried deep in the ground. • Heat and pressure can “bake” the rocks into new rocks called metamorphic rocks.
Rock Melting • Eventually, metamorphic rocks undergo enough heat that they melt and become magma again.
The Mantle • If rock is pushed deep enough it becomes part of the Mantle. • The Mantles is made of semi-molten rock (like magma) that is BELOW the earth’s crust. • The Mantle is constantly moving and molten rock exits the Mantle at oceanic ridges
Tectonic plates • Movement in the Mantle causes tectonic plates to move outwards unto they collide with other plates. Then, they are either subducted (go under) and reenter the mantle. Or, they create uplift and make mountains.
Let’s see this in action… • http://www.teachersdomain.org/resource/ess05.sci.ess.earthsys.rockcycle/
UNIFORMITARIANISM • People used to believe that the geologic processes that formed mountains were no longer taking place • This was called CATOSTROPHICISM. • People thought that the landscape (topography) of the Earth was formed by one giant CATOSTROPHE • Now, we know that the ROCK CYCLE explains that these processes having been going on forever and are still taking place. • It works because rock is recycled and mountains are simultaneously built up and worn down. • Now you know more than geologists did 150 years ago! • James Hutton, father of geology, “The present is the key to the past”.