The Rock Cycle “Where do rocks come from?”

Rocks and Minerals  Rocks are made of minerals.  Examples of minerals are:  Wakabayashilte, azurite, and galena.

Minerals change when:  They are heated  They are put under pressure

Heat and pressure comes from:  Earth’s inner workings (convection current)  Outer Earth forces (gravity, climate)

Without constantly changing heat and pressure  rocks would all be the same  geology would be very boring (no earthquakes, volcanoes or tsunami)

Because Earth is constantly changing:  Three major rock types: Igneous Metamorphic Sedimentary

One type of rock changes to another through:  Heat  Pressure  Erosion and deposition

This is called:  THE ROCK CYCLE

Reminder:  Magma is molten (melted) rock

Igneous Rocks  Form when magma solidifies

Types of Igneous Rock  Extrusive: when magma comes to the surface in a volcanic eruption

Types of Igneous Rock  Intrusive: when magma cools and solidifies slowly within the Earth  (note: intrusive rocks are found on the surface due to erosion, or uplifting)

Igneous rocks change:  Through weathering (aka: erosion) Wind Water Ice

The sediment is…  deposited on the sea floor  water pressure compacts and cements it

And becomes…  Sedimentary Rocks

Over time:  More layers of sediment are deposited  Pressure grows greater  Heat grows greater  The sedimentary rock recrystalizes (the minerals change again)

And becomes…  Metamorphic Rock

The temperature…  rises again  pressure increases  And the Metamorphic rock…

Becomes magma.  And the cycle begins again.

The End For Now…

Glossary Terms  Igneous (adj.) Formed by the solidification of molten rock; produced by volcanic heat.

Glossary (continued)  Metamorphic (adj.) A rock that has become more compact and more highly crystalline due to pressure and heat. A rock that has been changed. These are both examples of Gneiss – a type of metamorphic rock

Glossary (continued)  Sedimentary (adj.) Material deposited by water, wind, or glacier.