Rock- a solid, natural material made up of one or more minerals. • Geologist- scientists that study rocks and minerals.
Igneous Rock • Igneous Rock-Formed from lava or magma that has cooled and hardened. • INtrusive Igneous- Magma cool and crystalizes INside the earth. • EXtrusive Igneous- lava that has EXited the earth and cooled. Usually near a volcano. • Magma- Melted rock inside the earth • Lava- Melted rock outside the earth
Igneous comes from the latin word ignis meaning ‘fire’. • How is this meaning related to the definition of igneous rock?
Sedimentary Rock • Sedimentary Rock- rock formed from layers of sediment that have been cemented together. • Weathering- the process of breaking down rock into smaller pieces. • Sediments- small material such as stones and sand
Deposition- the process of dropping sediments onto a new place • Compaction- pressing down on that first layer of sediment, pushing most of the air and water out of it, pushing the particles closer together. • Cementation- loose sediments are glued together by natural glues like calcite and silica. • Fossils- remains of plants or animals that lived a long time ago or the evidence of them
Fun Facts • Sedimentary rocks are formed by sediment that is deposited over time, usually as layers at the bottom of lakes and oceans. • This sediment can include minerals, small pieces of plants and other organic matter. • Limestone is made from shells of tiny sea animals or from dissolved minerals that settle out of seawater.
Metamorphic Rock • Metamorphic Rock- existing rock changes from one type of rock to another because of heat and pressure. • Morph- to change or transform • Characteristics: • Formed when HEAT and PRESSURE change existing rock • Won’t usually have fossils (heat and pressure destroy them) • May include crystals- will be less than in igneous rock
How is Metamorphic rock formed? • Metamorphic means 'changed'. When a rock has been affected by metamorphic processes it has changed from one kind of rock to another. Metamorphic rocks can begin as igneous, sedimentary or other metamorphic rocks. They form when any kind of rock is exposed to high heat and high pressure over a long period of time. Extreme conditions like these for long periods can develop deep within the crust or where tectonic plates collide. • All metamorphic rocks have one thing in common, time. The longer a rock is exposed to one or all of the metamorphic stresses the more metamorphosed it becomes. • The creation of metamorphic rocks never involves melting the original rock. If these stresses do melt the original rock, an igneous rock is created. Metamorphic rocks change in the solid state by replacement or rearrangement of molecules. These changes are brought about by squishing, folding, and heating without ever melting!