Earth Science: Interior Layers and Plate Tectonics

Vocabulary flashcards covering key terms, compositional layers, rock types, and plate tectonic boundary types based on the lecture transcript.

Continental Crust

The lowest density layer of Earth ($2.8\,g\,cm^{-3}$), typically $0$ to $50\,\text{miles}$ thick with an average of $25\,\text{miles}$, composed mainly of silica-rich granitic rocks, quartz, and feldspar that is never recycled back into the mantle.

Oceanic Crust

A silicate layer denser than continental crust ($3\,g\,cm^{-3}$), ranging from $0$ to $6\,\text{miles}$ in thickness, mass-produced at divergent boundaries and composed primarily of dark, fine-grained basalt rich in iron and magnesium silicates.

Mantle

The silicate layer beneath the crust comprising $67.1\%$ of Earth's mass and $84\%$ of its volume, measuring $1,800\,\text{miles}$ in thickness with densities ranging from $3.3\,g\,cm^{-3}$ at the top to $6\,g\,cm^{-3}$ at the base.

Outer Core

A layer accounting for almost a third of Earth's mass, composed of a liquid molten iron alloy where moving currents generate Earth's magnetic field.

Inner Core

The solid, crystalline iron center of Earth, roughly the size of the Moon, making up $1.7\%$ of Earth's mass and representing Earth's hottest layer where extreme pressure prevents melting.

Peridotite

A coarse-grained rock characteristic of the mantle, consisting of dense green iron-magnesium silicate crystals and darker mineral grains that cooled slowly underground.

Basalt

A fine-grained, dark lava rock rich in iron and magnesium silicates that is characteristic of oceanic crust, formed when ocean water rapidly cools molten rock at seafloor spreading centers.

Granite

A coarse-grained igneous rock rich in silicon, oxygen, quartz, and feldspar that is characteristic of the continental crust.

Geotherm

The curve on Earth interior charts representing the actual temperature profile of Earth's layers from the surface to the center of the Earth.

Asthenosphere

A weak, deformable, partially molten zone within the upper mantle located between $60$ and $108\,\text{miles}$ depth over which Earth's tectonic plates move.

Lithosphere

The rigid, solid outer layer of Earth composed of the entire crust and the uppermost mantle, broken into approximately $15$ tectonic plates.

Divergent Plate Boundaries

Seafloor spreading centers where tectonic plates pull apart, exposing the asthenosphere to mass-produce standard $6\,\text{mile}$ thick oceanic crust and generating shallow-origin earthquakes.

Convergent Plate Boundaries

Plate boundaries where tectonic plates collide, categorized into oceanic-oceanic, oceanic-continental, and continental-continental collisions.

Transform Boundaries

Lateral or horizontal plate boundaries where plates slide past each other, producing shallow earthquakes but no volcanism.

Steady State Earth

The concept that Earth maintains a constant size because the creation of new oceanic crust at divergent boundaries is balanced by the subduction and recycling of old oceanic crust at convergent boundaries.

San Andreas Fault

A major transform plate boundary between the Pacific Plate and North American Plate in California that experiences shallow earthquakes but no volcanism because the North American plate overran the East Pacific Rise.

Tibetan Plateau

The highest plateau on Earth, supported by a buoyant $50\,\text{mile}$ thick continental crust resulting from the continental-continental collision of the Indian and Eurasian plates.

Himalayas

A non-volcanic mountain range formed as a crumpled zone of folded and faulted rocks created by the continental-continental convergence of the Indian plate sliding under Southern Eurasia.