| A | B |
|---|
| convergent plate boundary | Area where earth's lithospheric plates are pushed together. See subduction zone. |
| core | Inner zone of the earth. It consists of a solid inner core and a liquid outer core. |
| crust | Solid outer zone of the earth. It consists of oceanic crust and continental crust. |
| divergent plate boundary | Area where earth's lithospheric plates move apart in opposite directions. |
| earthquake | Shaking of the ground resulting from the fracturing and displacement of rock, which produces a fault, or from subsequent movement along the fault. |
| erosion | Process or group of processes by which loose or consolidated earth materials are dissolved, loosened, or worn away and removed from one place and deposited in another. |
| geology | Study of the earth's dynamic history. Geologists study and analyze rocks and the features and processes of the earth's interior and surface. |
| igneous rock | Rock formed when molten rock material (magma) wells up from the earth's interior, cools, and solidifies into rock masses. |
| lithosphere | Outer shell of the earth, composed of the crust and the rigid, outermost part of the mantle outside the asthenosphere; material found in earth's plates. |
| magma | Molten rock below the earth's surface. |
| mantle | Zone of the earth's interior between its core and its crust. |
| metamorphic rock | Rock produced when a preexisting rock is subjected to high temperatures (which may cause it to melt partially), high pressures, chemically active fluids, or a combination of these agents. |
| mineral | Any naturally occurring inorganic substance found in the earth's crust as a crystalline solid. |
| mineral resource | Concentration of naturally occurring solid, liquid, or gaseous material in or on the earth's crust in a form and amount such that extracting and converting it into useful materials or items is currently or potentially profitable. Mineral resources are classified as metallic (such as iron and tin ores) or nonmetallic (such as fossil fuels, sand, and salt). |
| other resources | Identified and undiscovered resources not classified as reserves. |
| plate tectonics | Theory of geophysical processes that explains the movements of lithospheric plates and the processes that occur at their boundaries. |
| tectonic plates (also plates) | Various-sized areas of the earth's lithosphere that move slowly around with the mantle's flowing asthenosphere. Most earthquakes and volcanoes occur around the boundaries of these plates. |
| reserves | Resources that have been identified and from which a usable mineral can be extracted profitably at present prices with current mining technology. |
| rock | Any material that makes up a large, natural, continuous part of the earth's crust. See mineral. |
| rock cycle | Largest and slowest of the earth's cycles, consisting of geologic, physical, and chemical processes that form and modify rocks and soil in the earth's crust over millions of years. |
| sedimentary rock | Rock that forms from the accumulated products of erosion and in some cases from the compacted shells, skeletons, and other remains of dead organisms. Compare igneous rock, metamorphic rock. |
| subduction zone | Area in which oceanic lithosphere is carried downward (subducted) under the island arc or continent at a convergent plate boundary. A trench ordinarily forms at the boundary between the two converging plates. |
| tectonic plates (also called plates) | Various-sized areas of the earth's lithosphere that move slowly around with the mantle's flowing asthenosphere. Most earthquakes and volcanoes occur around the boundaries of these plates. |
| transform fault | Area where the earth's lithospheric plates move in opposite but parallel directions along a fracture (fault) in the lithosphere. |
| tsunami | Series of large waves generated when part of the ocean floor suddenly rises or drops, usually because of an earthquake. |
| undiscovered resources | Potential supplies of a particular mineral resource, believed to exist because of geologic knowledge and theory, although specific locations, quality, and amounts are unknown. |
| volcano | Vent or fissure in the earth's surface through which magma, liquid lava, and gases are released into the environment. |
| weathering | Physical and chemical processes in which solid rock exposed at earth's surface is changed to separate solid particles and dissolved material, which can then be moved to another place as sediment. |
