Unit 1 Module 3 Key Words

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Continental Drift
The large-scale horizontal movement of continents during geological time
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Tillites
Ancient glacial deposits preserved within a rock sequence
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Evaporites
Minerals formed by the evaporation of saline water - e.g. halite (rock salt) and gypsum
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Apparent Polar Wandering Curve
Depicted by a line on a map which joins up the apparent positions of the magnetic north pole over time
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Magnetometer
Towed behind a ship to measure changes in magnetism - It can detect the strength and direction of the magnetic field
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Gravimeter
Can be towed behind a ship to measure changes in gravity
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Mafic
Igneous rocks with 45% to 52% silica (such as basalt)
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Pelagic
Applied to organisms living in, and sediment deposited from, the main body of sea water
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Planktonic
Applied to organisms that float in sea water
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Clastics
Sediments made up of fragments of pre-existing rock
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Continents
Situated on crust with an average thickness of 35km - Mean composition close to that of granite
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Ocean Basins
Situated on crust with an average thickness of 7km - Formed mainly of rocks with a basaltic composition
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Shallow-Focus Earthquakes
0 – 70 km deep
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Intermediate Focus Earthquakes
70 – 300 km deep
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Deep-Focus Earthquakes
300 – 720 km deep
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Benioff Zone
Marks a plane along which earthquakes are generated
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Subduction Zone
Where the downward movement of an oceanic lithospheric plate, beneath another plate, is ‘destroyed’ by partial melting as it descends into the mantle
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Lithosphere Plate
A layer or shell of the crust and upper mantle, in which the rocks are rigid and brittle - The base is taken as the 1300'C isotherm and varies in thickness
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Continental Plate
Carries a continent but will also have oceanic crust
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Oceanic Crust
Has no continental material
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Divergent Margins
Also called constructive as new material is added to the crust
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Convergent Margins
Also called destructive as oceanic crust is ‘lost’ along the subduction zones
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Hot Spot
A volcano within a plate which is the surface expression of a mantle plume
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Mantle Plume
A stationary area of high heat flow in the mantle which rises from great depths and produces magma that feeds hot spot volcanoes
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Diapir
A body of lower density, buoyant material rising upwards (in the same way as hot wax does in a larva lamp)
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Seismic Tomography
A computer imaging technique, based on seismic wave velocities
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Other cards in this set

Card 2

Front

Ancient glacial deposits preserved within a rock sequence

Back

Tillites

Card 3

Front

Minerals formed by the evaporation of saline water - e.g. halite (rock salt) and gypsum

Back

Preview of the back of card 3

Card 4

Front

Depicted by a line on a map which joins up the apparent positions of the magnetic north pole over time

Back

Preview of the back of card 4

Card 5

Front

Towed behind a ship to measure changes in magnetism - It can detect the strength and direction of the magnetic field

Back

Preview of the back of card 5
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