Igneous, Metamorphic and Sedimentary

A rock is a naturally formed, solid material made up of one or more minerals. What does naturally formed mean? What is a solid material? Minerals?

All rocks can fall into at least one of the categories. Rocks do not stay the same. They are continually changing. They change as a result of Melting. Heat and Pressure. Weathering, transportation, and deposition. Cementing and compacting. Cooling and solidifying.

Changed by HEAT AND PRESSURE. The word metamorphic actually means “changed”! Metamorphic rocks begin as either sedimentary, igneous or even other metamorphic rocks.

Develops underground. Rocks from above cause heat and pressure on the underlying metamorphic rock. Metamorphic rock is generally hard and nonporous. What does nonporous mean?

Rocks that form when small pieces of rocks, minerals and shells are deposited, buried and are squeezed and cemented together. Sometimes contains fossils.

Process of forming: Begins with weathering. What is weathering? Breaking down of existing rocks into smaller pieces. How? By wind, water and ice carry away these small rock pieces or SEDIMENT.

Making new rock. Eventually that sediment is deposited somewhere new. As sediment is added, it makes LAYERS. As the layers build up, it adds pressure the bottom layers are cemented together. Some rock layers are hard, solid and dense. Other layers are porous.

Forms when MELTED ROCK COOLS and HARDENS. Forms in two ways Intrusive Extrusive

Intrusive Over centuries trapped magma will cool and solidify (below ground) Extrusive When lava is cooled by the temperature of the air, it hardens to a solid.

Sedimentary rock forms in layers. Igneous rock forms from melting and cooling. Metamorphic rock forms from heat and pressure.