| A | B |
|---|
| geologists | scientists who study Earth and the processes that have shaped Earth over time |
| uniformitarianism | the principle that geologic processes operating today also operated in the past |
| crust | the rocky outer layer of Earth |
| silicates | a rock made of compounds of silicon and oxygen generally containing metals such as alluminum, iron, or calcium |
| mantle | a thick layer of hot but solid rock beneath Earth's crust |
| lithosphere | a layer of relatively cool, rigid rock that includes the uppermost part of the manlte as well as Earth's crust |
| asethenoshpere | a layer of softer, weaker rock beneath Earth's lithosphere, which can flow slowly |
| mesosphere | the lower portion of Earth's mantle |
| core | the dense sphere at Earth's center, made mostly of iron and nickel |
| rock | a solid combination of minerals or other materials |
| inorganic | a desription of a material that is not organic |
| streak | the color of a mineral's powder |
| hardness | teh resistance of a mineral to scratching |
| luster | the way a mineral's surface reflects light |
| fracture | teh way a mineral breaks, determined by the mineral's crystal structure |
| cleavage | a mineral's tendency to split along regular, well-defined planes |
| igneous rock | rock that forms from magma or lava |
| magma | a mixture of molten rock and gases, insluding water vapor,which forms underground |
| lava | magma that flows over Earth's surface |
| intrusive rock | an igneous rock that forms inderground from hardened magma |
| extrusive rock | an igneous rock that forms at Earth's surface |
| sediment | small, solid pieces of material that come from rocks or living things |
| sedimentary rock | rock that forms over time as sediment sqeezed and cemented together |
| clastic rocks | sedimentary rocks that form from the borken fragments of other rocks |
| metamorphice rock | rock that has been changed by temperature, pressure, or reactions with hot water. |
| foliated rocks | a metamorphic rock with crystaks arranged in parallel bands |
| rock cycle | a series of processes in which rocks continuously change from one type to another |
| plate tectonics | the theory that pieces of Earth's lithosphere, called plates, move about slowly on top of the asthenosphere |
| Pangea | an acient supercontinent formed about 300 million years ago, which later gave rise to today's continents |
| continental drift | the process in which the continents mvoe slowly across Earth's surface |
| mid-ocean ridge | a chain of underwater mountains |
| sea-floor spreading | the process by which new oceanic crust is created at mid-ocean ridges, as older crust moves away |
| subduction | the process by which oceanic crust sinks into the mantle through a trench |
| trench | a long, deep depression in the ocean floor where old oceanic crust sinks in the mantle |
| divergent boundary | a boundary at which tectonic playes move away from each other |
| convergent boundary | a boundary at which tectonic plates collide |
| transform boundary | a boundary at which tectonic plates slide past each other, moving in opposit directions |
| earthquake | a movement of Earth's crust that occurs when rocks in the crust suddenly shift, realeasing stored energy |
| seismic waves | vibrations that carry the energy released during an earthquake |
| tsunami | a large sea wave generated by an underwater earthquake, volcano, or landslide |
| stress | the forces of deformation acting on the rocks of Earth's crust |
| fault | a break in Earth's crust |
| fold | a bend in layers of rock |
| focus | the location beneath Earth's surface where an earthquake begins |
| epicenter | the point on Earth's surface directly above the focus of an earthquake |
| P waves | primary waves; longitudinal waves caused by earthquakes |
| S waves | secondary waves; transverse waves caused by earthquakes |
| surface waves | a transverse wave that develops when a seismic wave reaches Earth's surface |
| seismograph | a device that can detect and record seismic waves |
| volcano | a mountain that forms when magma reaches the surface |
| magma chamber | pocket in which magma collects before a volcanic eruption |
| pipe | a narrow vertical channel through which magma rises to Earth's surface |
| vent | an opening in the ground where amgma escapes to Earth's surface |
| crater | a bowl-shaped pit at the top of the central vent in a volcano |
