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33 Cards in this Set

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what is compression
Stress that reduces the volume or length of a rock, as that produced by the convergence of plate margins.
what is a continental collision
The convergence of two continental plates, resulting in the formation of mountain ranges
what is continental drift
The plate tectonics theory in earth science explains (among other things) “continental drift” – which itself is an earlier theory focusing on the jigsaw-puzzle-fit of South America and Africa.
what is a convection cell
The cycle of movement in the asthenosphere that causes the plates of the overlying lithosphere to move. Heated material in the asthenosphere becomes less dense and rises toward the solid lithosphere, through which it cannot rise further. It therefore begins to move horizontally, dragging the lithosphere along with it and pushing forward the cooler, denser material in its path. The cooler material eventually sinks down lower into the mantle, becoming heated there and rising up again, continuing the cycle.
what is convergence
The coming together of two lithospheric plates. Convergence causes subduction when one or both plates is oceanic, and mountain formation when both plates are continental.
what is a passive continental margin
A border that lies between continental and oceanic lithosphere, but is not a plate margin. It is marked by LACK of seismic and volcanic activity.
what is plate tectonics
The theory that the Earth's lithosphere consists of large, rigid plates that move horizontally in response to the flow of the asthenosphere beneath them, and that interactions among the plates at their borders cause most major geologic activity, including the creation of oceans, continents, mountains, volcanoes, and earthquakes
what is the principle of uniformitarianism
The scientific law stating that the geological processes taking place in the present operated similarly in the past and can therefore be used to explain past geologic events.
what is a hot spot
An area in the upper mantle, ranging from 100 to 200 kilometers in width, from which magma rises in a plume to form volcanoes. A hot spot may endure for 10 million years or more. The Hawaiian Islands developed over a hot spot . . . which is NOT at a plate margin.
what is lava
Magma that comes to the Earth's surface through a volcano or fissure
what is the lithosphere
A layer of solid, brittle rock making up the outer 100 kilometers of the Earth, encompassing both the crust and the outermost part of the upper mantle. The crust can be continental or oceanic.
what is magma
Molten (melted) rock that forms naturally within the Earth. Magma may be either a liquid or a fluid mixture of liquid, crystals, and dissolved gases.
what is the mantle
The middle layer of the Earth, lying just below the crust and consisting of relatively dense rocks.
what is an ocean trench
A deep, linear, relatively narrow depression in the sea floor, formed by the subduction of an oceanic plate.
what is rifting
The tearing apart of a plate to form a depression in the Earth's crust and often eventually separating the plate into two or more smaller plates
what is sea floor spreading
The formation and growth of oceans that occurs following rifting and is characterized by eruptions along mid-ocean ridges, forming new oceanic lithosphere, and expanding ocean basins.
what is subduction
The sinking of an oceanic plate edge as a result of convergence with a plate of lesser density. Subduction often causes earthquakes and creates volcano chains
what is topography
The set of physical features, such as mountains, valleys, and the shapes of landforms, that characterizes a given landscape
what is transform motion
The movement of two adjacent lithospheric plates in opposite directions along a parallel line at their common edge. Transform motion often causes earthquakes.
what is uniformitarianism
The hypothesis that current geologic processes, such as the slow erosion of a coast under the impact of waves, have been occurring in a similar manner throughout the Earth's history and that these processes can account for past geologic events
what is catastrophism
The hypothesis that a series of immense, brief, worldwide upheavals changed the Earth's crust greatly and can account for the development of mountains, valleys, and other features of the Earth.
what is a volcanic arc
A chain of volcanoes fueled by magma that rises from an underlying subducting plate
rocks on continents . . . what are they like?
continental rock is rich in silica and aluminum - it is not as dense as rock forming the ocean floor. It is sometimes called "sial".
what is rock on the ocean floor like?
ocean floor rock is rich in iron and magnesium - it is more dense than rock forming the continents. It is sometimes called "sima".
what type of rock is found in the lithosphere
continental, or oceanic, or both
what is the focus of an earthquake
The precise point WITHIN the Earth's crust or mantle where rocks begin to rupture or move in an earthquake
what is the epicenter of an earthquake
The point ON the Earth's surface that is located directly above the focus of an earthquake
what is a mid-ocean ridge
A continuous mountain range with a central valley, located on the ocean floor where two tectonic plates move away from each other allowing molten rock from the Earth's interior to move toward the surface.
what is the asthenosphere
A layer of soft but solid, mobile rock comprising the lower part of the upper mantle from about 100 to 350 kilometers beneath the Earth's surface.
what is the major evidence to support the plate tectonic theory
topographic: Coastal mountain ranges near subduction zones and offshore ocean trenches; mid-oceanic ridges

distribution of earthquakes:
Most earthquakes occur in narrow zones at mid-ocean ridges or in the Benioff Zone (descending band of earthquakes)

distribution of fossils:
re-connecting continents matches up fossil deposits
If ocean floors are being created continually, why doesn’t the earth get larger and wider?
The Earth does not get bigger with sea floor spreading because subduction occurs at convergent boundaries.
who was Hugo Benioff
In 1954, Hugo Benioff published a study of earthquakes near ocean trenches showing that the earthquake foci became deeper as epicenters were further inland
Except for reports of one death in an earthquake in Montreal in 1732, nobody has ever been killed by an earthquake in Canada. Why?
earthquakes aren't that intense in Candada. Canada is not near a subduction zone or a mid-ocean ridge where the most intense earthquakes occur.