| A | B |
|---|
| Rock | A mixture of one or more minerals, rock fragments, volcanic glass, organic matter, or other natural materials; can be igneous, metamorphic, or sedimentary |
| Rock cycle | A model that describes how rocks slowly change from one form to another through time |
| Lava | Molten rock that flows from volcanoes onto Earth’s surface |
| Igneous rock | Rock formed when magma or lava cools and hardens |
| Intrusive | Describes a type of igneous rock that generally contains large crystals and forms when magma cools slowly beneath Earth’s surface |
| Extrusive | Describes a type of igneous rock that generally contains fine (small) grains and forms when magma cools quickly at or near Earth’s surface |
| Basaltic | Describes dense, dark-colored igneous rock formed from magma rich in magnesium and iron and poor in silica |
| Granitic | Describes generally light-colored, silica-rich igneous rock that is less dense than basaltic rock |
| Metamorphic rock | Rock that forms when heat, pressure, or fluids act on igneous, sedimentary, or other metamorphic rock to change its form or composition, or both |
| Foliated | Describes metamorphic rock, such as slate and gneiss, whose mineral grains line up in parallel layers |
| Nonfoliated | Describes metamorphic rock, such as quartzite or marble, whose mineral grains grow and rearrange but generally do not form layers |
| Sediments | Loose materials, such as rock fragments, mineral grains, and the remains of once-living plants and animals, that have been moved by wind, water, ice, or gravity |
| Sedimentary rock | Rock that forms when sediments are compacted and cemented together or when minerals form from solutions |
| Compaction | Process that forms sedimentary rocks when layers of sediments are compressed by the weight of the layers above them |
| Cementation | Process that forms sedimentary rock when sediment grains are held together by natural cements that are produced when water moves through rock and soil |
