Introduction to Earth and Earth's Interior

Vocabulary practice flashcards covering introductory geology, planetary formation, density evidence, and Earth's compositional and mechanical layers based on GEOL 1403 Lesson 1.

Geology

The science of Earth that studies Earth's origin, history, materials, processes, and how the planet changes over time.

Big Bang

The event about $13.8\text{ billion}$ years ago in which time, space, energy, and matter began as the universe rapidly expanded from an extremely hot, dense state.

Solar Nebula Theory

The model describing how our solar system formed about $4.6\text{ billion}$ years ago when a cloud of interstellar gas and dust collapsed into a rotating disk.

Planetesimal

A small body formed from dust and gas in the young solar system.

Protoplanet

A growing planetary body made from colliding planetesimals.

Differentiation

The process driven by gravity in early Earth where materials separated by density, causing dense iron and nickel to sink toward the center while lighter silicates, water, and gases moved upward.

Earth's Average Density

The overall density of Earth, averaging about $5.51\,\text{g/cm}^3$, which reveals that Earth's interior must contain material denser than common surface rocks ($2.5-3.0\,\text{g/cm}^3$).

Seismic Wave

A vibration that travels through Earth after rock breaks and slips along a fault, used by scientists to infer internal boundaries and layer properties.

Mohorovicic Discontinuity (Moho)

The boundary between the crust and mantle where seismic P-waves speed up sharply.

Compositional Layers

The division of Earth's interior based on chemical makeup, consisting of the crust, mantle, and core.

Mechanical Layers

The division of Earth's interior based on physical behavior, consisting of the lithosphere, asthenosphere, mantle below the asthenosphere, outer core, and inner core.

Crust

Earth's outermost solid compositional layer, made mostly of silicate rock and serving as the primary source of Earth's surface resources.

Continental Crust

The thick ($30-70\,\text{km}$), old (up to $4.4\text{ billion}$ years), and less dense ($\sim 2.7\,\text{g/cm}^3$) crustal layer beneath land and shallow seas, composed of mixed rock types.

Oceanic Crust

The thin ($7-10\,\text{km}$), young ($180\text{ million}$ years old or younger), and denser ($\sim 3.0\,\text{g/cm}^3$) crustal layer beneath the deep-ocean floor, composed mostly of mafic basalt and gabbro.

Mantle

The thick silicate rock layer between the crust and core that is about $2,900\,\text{km}$ thick, making up $82\%$ of Earth's volume and $68\%$ of its mass.

Peridotite

An ultramafic rock rich in olivine and pyroxene that serves as the main rock of Earth's mantle.

Core

Earth's central compositional layer, composed mostly of iron with some nickel, accounting for $16\%$ of Earth's volume and $32\%$ of its mass.

Outer Core

The liquid mechanical layer of circulating iron alloy whose motion generates Earth's magnetic field.

Inner Core

The solid innermost mechanical layer, kept solid by enormous pressure despite temperatures of roughly $5,000-7,000\,^\circ\text{C}$.

Lithosphere

The cool, strong, and rigid mechanical layer consisting of the crust plus the uppermost mantle.

Asthenosphere

The hot, weak, plastic, and highly viscous solid mechanical layer located directly beneath the lithosphere in the upper mantle.

Anthropogenic

Caused by humans, such as climate change resulting from burning fossil fuels.

Aquifer

Rock or sediment that stores and carries groundwater.

Basalt

Dark, fine-grained mafic igneous rock common in oceanic crust.

Gabbro

Coarse-grained mafic igneous rock found in oceanic crust with a chemical composition similar to basalt.

Mafic

Silicate material or rock rich in iron and magnesium.

Ultramafic

Rock with very high magnesium and iron content, such as mantle peridotite.

Silicate

Mineral material built mainly from silicon and oxygen.

Viscous

Resistant to flowing.