Chapter 1 Vocabulary
| Word | Definition |
|---|---|
| abyssal plain | A very level area of the deep-ocean floor, usually lying at the foot of the continental rise. |
| asthenosphere | A subdivision of the mantle situated below the lithosphere. This zone of weak material exists below a depth of about 100 kilometers and in some regions extends as deep as 700 kilometers. The rock within this zone is easily deformed. |
| catastrophism | The concept that Earth was shaped by catastrophic events of a short-term nature. |
| continental shelf | The gently sloping submerged portion of the continental margin, extending from the shoreline to the continental slope. |
| continental slope | The steep gradient that leads to the deep-ocean floor and marks the seaward edge of the continental shelf. |
| craton | The part of the continental crust that has attained stability; that is, it has not been affected by significant tectonic activity during the Phanerozoic eon. |
| Earth system science | A field that aims to study Earth as a system composed of numerous interacting parts, or subsystems. |
| historical geology | A major division of geology that deals with the origin of Earth and its development through time. Usually involves the study of fossils and their sequence in rock beds. |
| lithosphere | The rigid outer layer of Earth, including the crust and upper mantle. |
| mantle | The 2885-kilometer thick layer of Earth located below the crust. |
| nebular hypothesis | A model for the origin of the solar system that assumes a rotating cloud of dust and gases that contracted to produce the Sun and planets. |
| oceanic ridge | A continuous mountain ridge on the floor of all the major ocean basins and varying in width from 500 to 5000 kilometers. The rifts at the crests of these ridges represent divergent plate boundaries. |
| relative dating | Rocks are placed in their proper sequence or order. Only the chronological order of events is determined. |
| seafloor spreading | The hypothesis first proposed in the 1960s by Harry Hess that suggested that new oceanic crust is produced at the crests of mid-ocean ridges, which are the sites of divergence. |
| seamount | An isolated volcanic peak that rises at least 1000 meters above the deep ocean floor. |
| shield | A large, relatively flat expanse of ancient metamorphic rock within the stable continental interior. |
| stable platform | That part of the craton that is mantled by relatively undeformed sedimentary rocks and underlain by a basement complex of igneous and metamorphic rocks. |
| superposition, law of | In any undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below. |
| transform fault | A major strike-slip fault that cuts through the lithosphere and accomodates motion between two plates. |
| transition zone | The lowest portion of the upper mantle. |
| uniformitarianism | The concept that the processes that have shaped Earth in the geologic past are essentially the same as those operating today. |