Rock Classification Igneous, Metamorphic and Sedimentary

Igneous Rocks The word Igneous comes from the Latin word ignis which means fire Igneous rocks come from magma

Magma formation There are three different ways that magma can form A change in Temperature Pressure Composition

A change in temperature When the temperature of an area rises it can cause a rock to melt into magma

A change in pressure If a rock heats up and rises pressure is released allowing the rock to melt into a liquid This is what happens when a rock rises from the center of the Earth moves closer to the crust **Remember the inner core is solid because of all the pressure

A change in composition If a fluid is combined with a rock it may lower the rocks melting point. Then the rock melts into magma We lower the boiling point of water when we add salt to it for Mac n Cheese

Felsic vs Mafic rocks Felsic rocks are light colored and have a lower density Mafic rocks are darker colored and have a higher density

Coarse grained vs Fine Grained Coarse grained rocks are formed when magma cools over long periods of time. The crystals have more time to grow Fine grained rocks cool quickly and the crystals don’t have a long time to grow

Intrusive Igneous Rocks Formed inside the crust of the Earth Usually coarse grained because the crust insulates the rock and allows it to cool slowly

Extrusive Igneous Rocks Rocks that form when magma erupts onto the Earth’s surface These rocks usually have fine or no crystals because the lava cools quickly