A broad, relatively flat region of the ocean that lies at least 4.5 km below sea level.
apparent polar wander patch
A path on the globe along which a magnetic pole appears to have wandered over time; in fact, the continents drift, while the magnetic pole stays fairly fixed.
The idea that continents have moved and are still moving slowly across the Earth's surface.
a narrow band of vertical fractures in the ocean floor; fracture zones lie roughly at right angles to a mmid ocean ridge.
transform vault: the actively slipping part of a fracture zone
The difference between the expected strength of the Earth's magnetic field at a certain location and the actual measured strength of the field at that location.
The change of the Earth's magnetic polarity; when a reversal occurs, the field flips from normal to reversed polarity, or vice versa.
mid ocean ridges
A 2-km-high submarine mountain belt that forms along a divergent oceanic plate boundary.
The Earth's outer shell is broken into rigid plates that move, these moving plates change the face of the Earth.
mantle is transferred to the surfaces and back down again
interior and surface of the Earth are in constant motion
explains earthquakes, volcanoes, and continental drift
sea floor spreading
The gradual widening of an ocean basin as new oceanic crust forms at a mid-ocean ridge axis and then moves away from the axis.
The rate at which sea floor moves away from a mid-ocean ridge axis, as measured with respect to the sea floor on the opposite side of the axis.
The process by which one oceanic plate bends and sinks down into the asthenosphere beneath another plate.
A deep elongate trough bordering a volcanic arc; a trench defines the trace of a convergent plate boundary.
a seamount that had a coral reef growing on top of it, so that now it is flat-crested
a wedge-shaped mass of sediment and rock scraped off the top of a downgoing plate and accumulated on the overriding plate at a convergent plate margin
the layer of the mantle that lies between 100-150 km and 350 km deep; this layer is relatively soft and can flow when acted on by force. flows plastically
the cloud of suspended minerals formed where hot water spews out of a vent along a mid-ocean ridge; the dissolved sulfide components of the hot water instantly precipitate when the water mixes with seawater and cools
the process by which a continent stretches and splits along a belt; if successful, this process separates a larger continent into two smaller continents separated by a divergent boundary
convergent plate boundary
a boundary at which two plates move toward each other so that one plate sinks (subducts) beneath the other; only oceanic lithosphere can subduct
divergent plate boundary
a boundary at which two lithosphere plates move apart from each other; they are marked by mid-ocean ridges
a relatively narrow, distinct belt of earthquakes that defines the position of a plate boundary
a narrow band of vertical fractures in the ocean floor that lie roughly at right angles to a mid-ocean ridge
global positioning system
a satellite system people can use to measure rates of movement of the Earth's crust relative to one another, or simply to locate their position on the Earth's surface
a location at the base of the lithosphere, at the top of a mantle plume, where temperatures can cause melting
the relatively rigid, nonflowable, outer 100-150- thick layer of the Earth; comprising the crust and the top part of the mantle
mid ocean ridge
a 2-km-high submarine mountain belt that forms along a divergent oceanic plate boundary
glass-encrusted basalt blobs formed when magma is extruded on the sea floor and cools very quickly
plate boundary volcano
a volcanic arc or mid-ocean ridge volcano, formed as a consequence of movement along the border between two adjacent lithosphere plates
a region away from the plate boundaries that consequently experiences few earthquakes
the crest of a mid-ocean ridge; the ridge axis defines the position of a divergent plate boundary
slab pull force
the force that downgoing plates (or slabs) apply to oceanic lithosphere at a convergent margin
the process by which one oceanic plate bends and sinks down into the asthenosphere beneath another plate
theory of plate tectonics
the theory that the outer layer of the Earth (the lithosphere) consists of separate plates that move with respect to one another
a fault marking a transform plate boundary; along mid-ocean ridges; these are the actively slipping segment of a fracture zone between two ridge segments
a deep elongate trough bordering a volcanic arc; defines the trace of a convergent plate boundary