Geology 101: Plate Tectonics and Earth's Systems Flashcards

Vocabulary practice flashcards covering key terms and definitions from Geology Day 1 lecture notes on Earth's systems, interior structure, continental drift, and plate tectonics.

Magnetosphere

The magnetic field that surrounds the Earth.

Geosphere

The solid Earth.

Atmosphere

The envelope of mixed gases that surrounds the Earth.

Hydrosphere

The Earth's liquid water.

Cryosphere

The Earth's frozen water.

Biosphere

All the Earth's living organisms and the regions they occupy.

Theory

An idea that has been supported by an abundance of evidence, has passed definitive tests, and has not yet fully failed a test.

Scientific Law

Statements that apply without exception for a given range of conditions, such as Newton's law of gravity.

Pangaea

A supercontinent hypothesized by Alfred Wegener where all Earth's continents were once joined together around 250 million years ago.

Mesosaurus

A freshwater reptile from the Permian period (~290 million years ago) whose fossils were found in both Africa and South America at the same time, supporting continental drift.

Continental Drift

The hypothesis that continents occupied different locations on Earth's surface in the geologic past.

Crust

The outermost chemical layer of Earth, comprising dense mafic oceanic crust ($7\text{--}10\,\text{km}$ thick) and less dense continental crust ($25\text{--}70\,\text{km}$ thick).

Mantle

The layer between Earth's crust and core that is ~$2900\,\text{km}$ thick and makes up 84% of Earth's volume.

Outer Core

A liquid iron alloy layer between $2900\,\text{km}$ and $5155\,\text{km}$ depth where rapid convection generates Earth's magnetic field.

Inner Core

A solid iron alloy sphere starting at $5155\,\text{km}$ depth that grows as the outer core cools and solidifies at a rate of about $1\,\text{mm}$ per year.

Differentiation of the Earth

The process early in Earth's history where melting allowed denser metallic material to sink to the center to form the core while lighter material formed the rocky mantle.

Moho

The boundary within the mantle defining the transition between Earth's crust and mantle.

Internal Energy

Heat stored in the Earth that drives internal processes such as volcanism.

External Energy

Energy arriving at Earth's surface from external sources, such as solar radiation.

Geothermal Gradient

The rate at which temperature increases with depth inside Earth, averaging about $25\,^\circ\text{C/km}$.

Mantle Convection

Slow, solid-state circulation of rock in Earth's mantle driven by density differences, where heated material rises and cooler material sinks.

Lithosphere

A rigid layer comprising the crust and the uppermost mantle that bends or breaks when force is applied.

Asthenosphere

The ductile layer of the mantle directly below the lithosphere that is hot enough to flow slowly when subjected to force.

Oceanic Lithosphere

Thin, dense lithosphere composed predominantly of mafic rock.

Continental Lithosphere

Thick, less dense lithosphere composed of felsic and intermediate rock.

Theory of Plate Tectonics

The theory that Earth's lithosphere is divided into discrete plates that move relative to each other over the asthenosphere.

Seafloor Spreading Hypothesis

The hypothesis that new ocean crust is continuously formed at mid-ocean ridges and spreads laterally away, widening ocean basins.

Subduction

The process by which older, denser oceanic lithosphere slides down into the mantle at deep-sea trenches beneath an overriding plate.

Divergent Boundary

A plate boundary where two tectonic plates move away from each other.

Convergent Boundary

A plate boundary where two tectonic plates move toward each other.

Transform Boundary

A plate boundary where two tectonic plates slide horizontally past one another along a vertical fault plane.

Hotspot

A fixed location within the mantle over which tectonic plates move, producing volcanic chains such as the Hawaiian Islands.

Volcanic Arc

A chain of volcanoes formed on an overriding plate along a subduction zone, which can be continental or an island arc.

Passive Margin

The stable geological transition boundary between continental crust and oceanic crust within a single plate that is not an active plate boundary.

Continental Shelf

The underwater edge of a continent covered by a shallow layer of ocean water.

Accretionary Prism

A wedge-shaped mass of sediment and crust scraped off as the downgoing plate slides against the overriding plate at a subduction zone.

Wadati-Benioff Zone

A zone of earthquakes occurring along the inclined interface of a subducting oceanic plate.

Fracture Zone

A feature laterally continuous with transform boundaries that exists within a single plate rather than between two moving plates.

Slab Pull

The gravitational force developed as cold, dense oceanic lithosphere sinks into the asthenosphere, pulling the rest of the tectonic plate with it.

Ridge Push

The force driving plate motion developed due to the higher elevation of mid-ocean ridges compared to bordering abyssal plains.

Asthenosphere Shear

The drag force exerted on the base of tectonic plates by convective motion in the asthenosphere.

Triple Junction

A location where three tectonic plate boundaries intersect.

Linear Island Chains

Chains of submarine volcanoes and islands created as a tectonic plate moves over a fixed hotspot.

Mountain Belts

Prominent mountain ranges created by tectonic forces at convergent plate boundaries, such as Denali, the Andes, and the Himalayas.