Chapter 2 Vocabulary
| Word | Definition |
|---|---|
| continental drift | A hypothesis, credited largely to Alfred Wegener, which suggested that all present continents once existed as a supercontinent. Further, beginning around 200 million years ago, the supercontinent began breaking into smaller continents, which then "drifted" to their present positions. |
| convection | The transfer of heat by the mass movement or circulation of a substance. |
| convergent plate boundary | A boundary in which two plates move together, resulting in oceanic lithosphere being thrust beneath an overriding plate, eventually to be reabsorbed into the mantle. It can also involve the collision of two continental plates to create a mountain system. |
| Curie point | The temperature above which a material loses its magnetization. |
| deep-ocean trenches | A narrow, elongated depression of the seafloor. |
| divergent plate boundary | A boundary in which two plates move apart, resulting in upwelling of material from the mantle to create a new seafloor. Also called spreading center. |
| fracture zone | A linear zone of irregular topography on the deep-ocean floor that follows transform faults and their inactive extensions. |
| hot spot | A concentration of heat in the mantle, capable of producing magma, that, in turn, extrudes onto Earth's surface. |
| island arc | A chain of volcanic islands generally located a few hundred kilometers from a trench where there is active subduction of one oceanic plate beneath another. |
| magnetic reversal | A change in Earth's magnetic field from normal to reverse or vice versa. |
| magnetometer | A sensitive instrument used to measure the intensity of Earth's magnetic field at various points. |
| mantle plume | A mass of hotter-than-typical mantle material that ascends toward the surface, where it may lead to igneous activity. |
| paleomagnetism | The natural remnant magnetism in rock bodies. It can be used to determine the location of the magnetic poles and the latitude of the rock at the time it was magnetized. |
| Pangaea | The proposed supercontinent that 200 million years ago began to break apart and form the present landmasses. |
| partial melting | The process by which most igneous rocks melt. Since individual minerals have different melting points, most igneous rocks melt over a temperature of a few hundred degrees. |
| ridge push | A mechanism that may contribute to plate motion. It involves the oceanic lithosphere sliding down the oceanic ridge under the pull of gravity. |
| rift valley | A long, narrow trough bounded by normal faults. It represents a region where divergence is taking place. |
| slab pull | A mechanism that contributes to plate motion in which cool, dense oceanic crust sinks into the mantle and "pulls" the trailing lithosphere along. |
| subduction zone | A long, narrow zone where one lithospheric plate descends beneath another. |
| supercontinent | A large landmass that contains all, or nearly all, of the existing continents. |
| theory of plate tectonics | A well-tested theory proposing that Earth's outer shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself. |
| transform fault | A major strike-slip fault that cuts through the lithosphere and accommodates motion between two plates. |