Earth’s Dynamic Crust: Volcanoes, Earthquakes, and Mountain Ranges – Key Vocabulary

32 vocabulary flashcards covering Earth structure, plate motions, boundary types, and related geologic features

Crust

Earth’s thin, outermost solid layer

Mantle

Semi-solid layer beneath the crust composed of hot rock that slowly flows

Outer Core

Liquid layer of molten iron and nickel surrounding the inner core

Inner Core

Solid metallic center of the Earth, mostly iron and nickel

Lithosphere

Rigid layer made of the crust and uppermost mantle; broken into tectonic plates

Asthenosphere

Plastic, semi-fluid portion of the upper mantle on which plates float

Tectonic Plate

Large, rigid piece of the lithosphere that moves over the asthenosphere

Plate Tectonics Theory

1960s theory stating that Earth’s lithospheric plates move due to mantle convection, slab pull, and ridge push

Continental Drift Theory

Alfred Wegener’s 1912 idea that continents once formed Pangaea and have since drifted apart

Pangaea

Supercontinent that began breaking apart about 200 million years ago

Convection Currents

Mantle circulation in which hot material rises and cool material sinks, driving plate movement

Slab Pull

Force exerted by a sinking, subducting plate that drags the rest of the plate downward

Ridge Push

Gravity-driven force that moves plates away from elevated mid-ocean ridges

Divergent Boundary

Plate boundary where plates move apart, creating mid-ocean ridges and new crust

Mid-Ocean Ridge

Undersea mountain chain formed at a divergent boundary where magma creates new seafloor

Seafloor Spreading

Process of new oceanic crust forming at mid-ocean ridges and moving outward

Convergent Boundary

Plate boundary where plates move toward each other, often causing subduction or collision

Oceanic–Oceanic Convergence

Collision of two oceanic plates where the denser plate subducts, forming trenches and volcanic island arcs

Volcanic Island Arc

Curved chain of volcanic islands created above a subducting oceanic plate

Ocean Trench

Deep linear depression in the ocean floor at a subduction zone

Oceanic–Continental Convergence

Subduction of an oceanic plate beneath a continental plate, forming trenches and continental volcanic arcs

Continental Volcanic Arc

Line of volcanoes on a continent formed above a subducting oceanic plate

Continental–Continental Convergence

Collision of two continental plates, producing thickened crust and fold mountains

Fold Mountains

Large mountain ranges formed by crustal compression and folding (e.g., Himalayas)

Transform Boundary

Plate boundary where plates slide horizontally past each other, generating faults and earthquakes

Fault

Fracture in Earth’s crust along which movement has occurred

San Andreas Fault

Major transform fault in California where the Pacific Plate slides past the North American Plate

Earthquake

Sudden release of energy in Earth’s crust causing ground shaking, usually at plate boundaries

Triangulation Method

Technique using data from three or more seismic stations to locate an earthquake’s epicenter

Major Tectonic Plates

The seven largest plates: Pacific, North American, South American, African, Eurasian, Antarctic, Indo-Australian

Pacific Plate

Earth’s largest tectonic plate, mostly oceanic, bounded by many active margins