Lecture 8: Plate Tectonics

This flashcard set explores plate tectonics and boundaries, earthquakes, and Earth's layers. It includes key concepts about tectonic plate movements, types of plate boundaries, earthquake mechanics, and the structure of Earth's interior.

Accretion

The gradual accumulation of sediments, volcanic material, or other geological matter, which can lead to the formation of landforms such as deltas, sandbars, and alluvial fans.

Accretion Wedge

A zone where material is scraped off of a subducting plate and compressed into the continental margin; oldest material at top, youngest at bottom (reverse of superposition).

Active margin

A continental margin characterized by significant tectonic activity, such as earthquakes, volcanic eruptions, and mountain building, occurring at the boundaries of converging, diverging, or transforming tectonic plates.

Alfred Wegener

German meteorologist who proposed the hypothesis of Continental Drift and used the similarity of coast lines to propose a past supercontinent; coined the term Pangea.

Apparent polar wandering

The perceived movement of Earth's magnetic poles relative to a continent, caused by the drift of tectonic plates rather than actual pole movement.

Arthur Holmes

Hypothesized convection currents in the mantle as a mechanism for continental drift; observations not available to test his hypothesis.

Asthenosphere

A weak, hot, and semi-fluid layer of the Earth's mantle beneath the lithosphere that allows tectonic plates to move.

Bathymetry

The measurement of ocean floor topography.

Body waves

Seismic waves that travel through the Earth's interior. They are responsible for the initial shaking felt during an earthquake.

Climate belts

Regions with similar climate conditions, like temperature and rainfall, influenced by their distance from the equator and other factors.

Compressional

A force that squeezes rocks together, causing them to fold, break, or become denser; often happens at places where tectonic plates collide.

Continental Drift

The idea that Earth's continents have moved over time and were once joined together in a single supercontinent.

Convection currents

Rising and sinking cycle of mantle material driven by heat from Earth's core, influencing plate tectonics.

Convergent plate boundaries

Tectonic plate boundaries where plates move towards each other, leading to mountain formation, subduction zones, or island arcs; compression.

Core

The innermost layer of the Earth, consisting mainly of iron and nickel, and is divided into a solid inner and a liquid outer; generates a magnetic field.

Crust

The outermost layer of the planet, consisting of solid rock; divided into continental and oceanic types.

Dipole

Two ends of opposite polarity

Divergent plate boundaries

Tectonic plate boundaries where plates move apart, creating features like mid-ocean ridges and rift valleys; tension.

Earthquake

The shaking of the ground caused by the sudden release of energy from deep within the Earth.

Extension

The stretching and thinning of crust.

Fossil distribution

Identical or similar fossils are found on widely separated continents.

Geophysics

The study of the Earth's physical properties and processes using principles of physics.

Hot spots

Areas of volcanic activity not at plate boundaries, formed by rising plumes of hot material from the mantle; eventually forms a volcano.

Lithosphere

The strong, cold, and rigid outer layer of the Earth, consisting of the crust and the upper part of the mantle.

Magnetic field

The region around the Earth or a rock body where magnetic forces are present, often generated by the movement of molten iron in the Earth's core.

Magnetic field reversal

When the Earth's magnetic north and south poles switch places.

Mantle

The thick layer of rock between the Earth's crust and core, involved in tectonic activity and heat transfer.

Metamorphism

The process where existing rocks are changed into new types of rocks through heat, pressure, or chemical reactions.

Mid-ocean ridge

Underwater mountain ranges formed by divergent tectonic plates where new oceanic crust is created.

Mohorovicic discontinuity (Moho line)

The boundary between Earth's crust and mantle; it marks a change in the speed of seismic waves.

Mountains

Large landforms that rise prominently above their surroundings, typically formed by tectonic forces or volcanic activity.

P-wave

A fast moving seismic wave that compresses and expands the ground as it travels through solids and liquids; rises first.

Paleomagnetism

The study of the Earth's past magnetic fields recorded in rocks.

Pangea

Supercontinent; means “all of earth”.

Partial melting

The process where only a portion of a rock melts, forming magma while the rest remains solid.

Passive margin wedge

A sedimentary accumulation formed when plates gradually sink as the hot oceanic crust shrinks and subsides.

Planetary differentiation

The process by which a planet separates into different layers, such as the core, mantle, and crust, based on the density and composition of its materials.

Plate tectonics

The theory that the Earth's outer shell is divided into several large, moving plates that interact at their boundaries, causing geological activities like earthquakes and volcanism.

Rift

A linear zone where the Earth's crust is being pulled apart, leading to the formation of a valley or a rift zone.

S-wave

A slow seismic wave that moves perpendicular to direction of motion and travels only through solids; rises second.

Seafloor spreading

New oceanic crust forms and spreads, expanding the ocean floor.

Seismic waves

Waves of energy released during an earthquake, used to determine Earth’s internal zones' location, thickness, and properties.

Seismogram

A record of the ground motions caused by seismic waves.

Seismometer

An instrument that detects and measures these vibrations.

Shadow zones

Areas on Earth's surface where seismic waves from an earthquake are not detected due to refraction and reflection by Earth's layers.

Sonar

A technique that uses sound waves to map and explore underwater features, such as the seafloor and submerged structures.

Striations

Grooves or scratches on rocks caused by the movement of glaciers or other geological processes.

Strike-slip

A type of fault movement where two blocks of rock slide past each other horizontally along the fault line.

Subduction

The process where one tectonic plate is forced beneath another into the Earth's mantle.

Surface waves

Large motion waves that travel through outer crust (solid); main cause of destruction during earthquakes.

Transform plate boundaries

Tectonic plate boundaries where plates slide past each other horizontally, causing strike-slip faults and shallow earthquakes.

Trench

A deep, narrow depression in the ocean floor, often formed by the subduction of one tectonic plate beneath another.

Volcanic arc

A chain of volcanoes formed above a subduction zone where one tectonic plate is forced under another, causing magma to rise and create volcanoes.