Flashcard: Earth's Interior and Surface Contrasts — 20 carte

Bimodal Altitude Distribution — definition?

Two distinct peaks: oceanic (-4500 m) and continental (+300 m).

Crust composition — continental rocks?

Primarily granite, silica-rich, coarse-grained, ~2.7 density.

Crust composition — oceanic rocks?

Mainly basalt and gabbro, mafic, denser (~2.9), fine- to coarse-grained.

Moho discontinuity — role?

Separates crust from mantle, marked by seismic velocity increase.

Gutenberg discontinuity — depth?

Approximately 2900 km, separates mantle from outer core.

Lehmann discontinuity — significance?

Divides outer liquid core from inner solid core at ~5100 km.

Seismic wave — types?

P-waves (compressional) and S-waves (shear).

Discontinuity — seismic signature?

Velocity jumps, reflections, refractions at layer boundaries.

Low Velocity Zone — location?

100-200 km depth, marks lithosphere-asthenosphere boundary.

Thermal gradient — typical value?

Approximately 30°C/km in lithosphere, ~0.3°C/km in mantle.

Heat transfer mode — dominant in mantle?

Convection, large-scale material movement.

Conduction — primary in?

Earth's crust, especially in rigid lithosphere.

Thermal anomaly — example?

Hot spots (positive), subduction zones (negative).

Mantle plume — effect?

Creates localized positive thermal anomalies, volcanic activity.

Seismic wave refraction — indicates?

Changes in wave speed at layer boundaries.

Discontinuity of Moho — depth variation?

7 km under oceans, up to 30 km under continents.

Gabbro — texture?

Coarse-grained (grenue), intrusive mafic rock.

Basalt — texture?

Fine-grained (microlitique), volcanic mafic rock.

PREM model — purpose?

Describes Earth's layered internal structure from seismic data.

Seismic shadow zone — caused by?

Refraction in the outer core, absence of S-waves.