Earth Structure Key Words Flashcards
Discontinuity
A zone within the earth where a sudden change in physical properties occur
Asthenosphere
A layer within the upper mantle where there is 5% partial melting as a result of the intersection of the geothermal gradient and the melting curve of peridotite
Ophiolites
Sections of the earths oceanic crust that have been tectonically moved into continental crust
Peridotite
An ultramafic igneous rock composed of the minerals olivine and pyroxene
Rhied
A non-molten solid that deforms by viscous or plastic flow in response to an applied force
Seismic tomography
A technique for 3D imagining of the subsurface of the earth using seismic waves
Xenoliths
Pieces of rock within an igneous rock which have not been derived from the original magma but have been introduced from elsewhere. These are usually from the surrounding country rock
Low velocity zone
Is characterised by low seismic velocities
Lithosphere
The upper rigid layer of the crust and upper mantle
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
Isostasy
The theoretical state of equilibrium between the earth lithosphere and asthenosphere such that the lithosphere ‘floats’ at an elevation that depends on its thickness and density. The less dense continents rise to a higher elevation than the dense oceanic floors although the pressure exerted on the underlying asthenosphere is the same
Kimberlite pipes
The result of explosive volcanism from deep mantle sources
Gravity anomalies
Gravity itself cannot be used to identify a particular rock type because too many variables are involved. It is more useful to plot the variations in values from place to place
Palaeomagnetism
Ancient magnetism preserved in rocks
