Lecture 5: Plate Tectonics - Vocabulary Flashcards

Vocabulary-style flashcards covering key concepts from the plate tectonics lecture notes, including terms related to mantle convection, plate boundaries, crust types, subduction, and related Mars data from InSight.

InSight

NASA/Jet Propulsion Laboratory mission that studied Mars’ interior, revealing a molten silicate layer over the core.

Molten silicate layer

Partially molten rock above a planet’s metallic core that affects seismic wave travel.

Mantle convection

Movement of the mantle driven by heat differences, thought to drive plate tectonics through upwelling and downwelling.

Ridge push

Gravity-driven sinking of cooling lithosphere at mid-ocean ridges, pushing tectonic plates away from the ridge.

Slab pull

Sinking of cold, dense oceanic lithosphere at a subduction zone, pulling the rest of the plate with it.

Subduction zone

Plate boundary where one plate sinks beneath another into the mantle.

Accretionary wedge

Sediment and rock wedge scraped off the subducting plate at a subduction zone.

Volcanic arc

Curved chain of volcanic islands or mountains formed above a subduction zone.

Lithosphere

Rigid outer layer of Earth, comprising the crust and uppermost mantle.

Asthenosphere

Weak, partially molten layer beneath the lithosphere that allows plate movement.

Oceanic crust

Thin, dense crust (about 7 km thick) made primarily of basalt, with density ~3.0 g/cm3.

Continental crust

Thick, buoyant crust (about 40 km) made mainly of granitic rocks, density ~2.7 g/cm3.

Density

Mass per unit volume; in geology, density contrasts influence buoyancy and subduction.

Density–temperature relationship

Higher temperature → larger volume → lower density; lower temperature → smaller volume → higher density.

Mid-Ocean Ridge

Underwater mountain range where seafloor spreading occurs as plates move apart.

Seafloor spreading

Formation of new oceanic crust at mid-ocean ridges as tectonic plates diverge.

Passive margin

Continental margin with no active plate boundary; tectonically quiet region.

Active margin

Continental margin located at an active plate boundary with tectonic activity.

Divergent plate boundary

Boundary where two plates move apart; often at mid-ocean ridges or continental rifts.

Convergent plate boundary

Boundary where plates collide; includes ocean–ocean, ocean–continent, and continent–continent interactions.

Ocean–ocean convergence

Two oceanic plates converge; one subducts beneath the other, forming trenches and arcs.

Ocean–continent convergence

Oceanic plate subducts beneath continental plate; forms trenches and volcanic arcs.

Continental–continent convergence

Two continental plates collide; forms mountain belts without subduction of buoyant continental crust.

Transform plate boundary

Boundary where plates slide past one another horizontally; earthquakes common, little volcanism.

Seven major tectonic plates

Earth’s largest plates (plus many minor ones) that move a few centimeters per year.

Plate velocity

Typical movement rate of plates, measured in centimeters per year.

Age of oceanic lithosphere

Young near mid-ocean ridges, aging and cooling with distance from ridges.

Crustal thickness

Oceanic crust ~7 km thick; continental crust ~40 km thick.

Crustal densities

Oceanic crust ~3.0 g/cm3; continental crust ~2.7 g/cm3; upper mantle ~3.3 g/cm3.

Scientific method steps (observations to theories)

Make observations → formulate hypothesis → develop testable predictions → gather data → develop theories → refine or reject hypotheses.

Abyssal plain

Flat, deep ocean floor region beyond continental margins.

Planetary density contrasts and subduction

Denser plate subducts beneath less dense plate at boundary zones.