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CHAPTER 8 VOCABULARY
Term | Definition |
---|---|
Geology | Study of the structure of planet Earth and the forces that make and shape Earth. |
Uniformitarianism | Geologic processes that operated today also operated in the past. |
Igneous Rocks | Form when molten material beneath Earth's surface cools and hardens. |
Sedimentary Rocks | Made of sediments that have been deposited and then pressed together. |
Metamorphic Rocks | Form when an existing rock is changed by heat, pressure, or chemical reactions. |
Rock Cycle | A series of processes on and beneath Earth's surface that slowly change rocks from one kind to another. |
Magma | Molten material beneath Earth's surface. |
Lava | Magma that flows to the surface. |
Relative Age | The age of a rock compared to the ages of other rocks. |
Absolute Age | The number of years since the rock formed. |
Law of Superposition | In horizontal rock layers, the oldest is at the bottom and the youngest is at the top. |
Extrusion | Lava that hardens on the surface. |
Intrusion | Igneous rock formed when magma cools and hardens. |
Fault | A break in Earth's crust. |
Unconformity | The surface where new rock layers meet a much older rock surface beneath them. |
Inclusion | A piece of rock contained in another rock. |
Index Fossil | A widely distributed organism that existed briefly. |
Atom | The small particles that make up matter. |
Element | When all atoms in a particular type of matter are the same. |
Radioactive Decay | The process in which the atoms of one element break down to form atoms of another element. |
Half Life | Time it takes for half of the radioactive atoms to decay. |
Erosion | Process in which natural processes break down rocks and carry away the pieces. |
Geologic Time Scale | A record of life forms and and geologic events in Earth's history. |
Era | Three long units between Precambrian and present. |
Period | Subdivision of era. |
Invertebrates | Animals without backbones. |
Vertebrates | Animals with backbones. |
Amphibian | Animal that lives on land and water. |
Reptile | Vertebrate with scaly skin and leathery, tough shelled eggs. |
Mass Extinction | Event in which many different organisms die at the same time. |
Mammal | Warm blooded vertebrate that feeds its young milk. |