1. HOW ROCKS FORM By: Ms. Avery

2. Types of Rocks  Igneous Rocks: Rocks formed by magma  Intrusive: form when magma hardens beneath Earth’s surface  Extrusive: when lava hardens on surface of Earth  Metamorphic Rock: Form when existing rocks are changed by heat and pressure  Foliated: When rocks under pressure or when minerals crystallize to form “bands” or folds in the rock  Non-foliated: no banded texture

3. Types of Rocks  Sedimentary Rocks: Form when solids settle our of a fluid such as water or air  Clastic: weathered bits of rocks and minerals Ex. Clay, Quartz  Chemical (or Biochemical): when dissolved minerals precipitate from water solutions Ex. Limestone, rock salt, flint

4. Sedimentary Rocks (continued)  Caused by:  Weathering Physical: water, wind, ice, gravity Chemical: reactions with water, acid rain, or other chemicals  Erosion: caused by weathering and removal of rock  Deposition: depositing of rock  Compaction: squeezes or compacts rocks  Cementation: dissolved minerals are deposited in cracks of sediments

5. continued  Foliation is when trees or other plants grow up through a rock and cause it to weaken.  Bedding is when rocks build up on the edge of a water source such as a river.