Earth's Internal Heat Sources - Vocabulary

Vocabulary flashcards covering key terms from the lecture on magma, internal heat sources, and related geologic processes.

Magma

Underground molten rock and dissolved gases formed in the Earth's mantle or core; temperature about 500–1200°C; major elements include O, Si, Al, Fe, K, Na, Mg, Ca; oxygen is the most abundant element.

Lava

Magma that has erupted onto the Earth's surface.

Endogenic process

Geologic processes formed, originated, and located below the Earth's surface (e.g., tectonics, metamorphism, seismicity, magmatism).

Primordial heat

Heat left over from Earth’s formation when particles collided and differentiated the planet into layers.

Radioactive decay

Heat produced by the breakdown of radioactive elements inside the Earth.

Volcanism

All geological phenomena involving the flow and transport of igneous material from the planet’s interior toward the surface.

Extrusion

Eruption of magmatic materials that reach the surface and form volcanic landforms.

Intrusion

Magma moving upward without erupting, becoming embedded in the crust (underground solidification).

Plutonism

Magma produced by melting that cools and crystallizes underground, forming plutons.

Plutonic rocks

Rocks crystallized underground from magma (e.g., granite) before reaching the surface.

Decompression melting

Melting caused by a drop in pressure as rocks rise in the mantle, common at mid-ocean ridges.

Flux melting

Melting driven by volatiles (like H2O, CO2) that lower the rocks’ melting point, common at subduction zones.

Heat transfer melting

Melting caused by transfer of heat from hot magma to surrounding rocks, such as at hotspots.

Partial melting

Melting where minerals melt at different temperatures, producing magmas with varied compositions.

Volatile

Substances (e.g., water, CO2) that lower melting temperatures when added to rocks.

Density contrast

Difference in density between magma and surrounding country rock; greater contrast promotes faster ascent.

Viscosity

A fluid’s resistance to flow; low viscosity magma flows easily; mafic magma is less viscous than silicic due to higher temperature and lower silica.

Magma differentiation

Evolution of magma composition through processes like fractionation, assimilation, mixing, and crystal settling.

Crystal fractionation

As magma cools, early-formed crystals settle out, leaving a melt richer in silica and progressing from mafic to felsic.

Magmatic assimilation

Magma melts and incorporates surrounding country rock, altering its chemical composition.

Magma mixing

Two different magmas meet and mix to produce a hybrid composition.

Crystal settling

Dense crystals sink to the bottom of the magma chamber, leaving the melt enriched in lighter elements.

Mantle convection

Convection currents in the mantle that drive plate tectonics and moving continents.

Seafloor spreading

Magma rising at mid-ocean ridges forms new oceanic crust as it reaches the surface and cools.

Volcanites

Rocks formed when lava crystallizes at the Earth’s surface; a major category of igneous rocks.

Phreatomagmatic eruption

An eruption driven by interaction between magma and groundwater.