Earth's Dynamic Layers and Tectonic Processes Vocabulary

Vocabulary flashcards covering Earth's layers, plate tectonics, folding, faulting, earthquakes, volcanoes, and human responses based on the provided lecture notes.

Crust

The outer layer of Earth, ranging from $5-70\,\text{km}$ thick, which contains landforms, rocks, and soil.

Mantle

The layer of Earth beneath the crust that is $2900\,\text{km}$ thick, mostly solid but soft, with upper parts that can partially melt into magma.

Outer core

A molten layer of Earth about $2300\,\text{km}$ thick, composed mainly of iron and nickel.

Inner core

The solid innermost layer of Earth, about $1200\,\text{km}$ thick and composed mainly of iron, with temperatures up to $7000^\circ\text{C}$.

Lithosphere

The solid outer layer of Earth that includes the crust and upper mantle, which can break under stress.

Focus

The point deep inside Earth where an earthquake begins.

Epicentre

The point on Earth's surface directly above the focus of an earthquake.

Continental crust

The crust that makes up land, ranging from $25-70\,\text{km}$ thick, with a density of $2.7\,\text{g/cm}^3$ and a composition similar to granite.

Oceanic crust

The crust that forms ocean floors, ranging from $4-10\,\text{km}$ thick, with a density of $3.0\,\text{g/cm}^3$ and a composition similar to basalt.

Ophiolites

Pieces of oceanic crust found on land, such as Macquarie Island, that help scientists study the ocean floor.

Alfred Wegener

The scientist who proposed the theory of continental drift in $1912$, suggesting all continents were once joined together.

Pangaea

An ancient supercontinent surrounded by the Panthalassa Ocean that began breaking apart about $200\,\text{million years}$ ago.

Sea-floor spreading

The process where hot mantle material rises and erupts at ocean ridges, cooling to form new oceanic crust and pushing older crust away.

Marie Tharp

A geologist and cartographer who mapped the ocean floor using sonar data, discovering a $16\,000\,\text{km}$ mountain ridge with a central rift.

Plate tectonics

The modern theory stating that Earth's lithosphere is broken into large plates that move over a weaker mantle below and interact at their boundaries.

Mantle convection currents

Slow-moving currents created when hot mantle material rises and cooler material sinks, carrying tectonic plates above them.

Slab pull

The strongest force moving tectonic plates, occurring when older, colder, denser crust sinks into the mantle like an anchor, pulling the rest of the plate.

Ridge push

A force moving tectonic plates where gravity causes warm, elevated newly formed crust at ocean ridges to move downward and outward.

Convergent boundary

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

Subduction zone

A destructive boundary region where older, heavier oceanic crust sinks beneath another plate into the mantle.

Ring of Fire

A region around the Pacific Ocean containing many subduction zones and the majority of the world's active volcanoes.

Divergent boundary

A constructive boundary where tectonic plates move apart, allowing hot mantle rock to rise and create new crust.

Mid-Atlantic Ridge

The largest divergent boundary on Earth, spreading at about $2.5\,\text{cm}$ per year.

Transform boundary

A conservative boundary where two tectonic plates slide past each other without creating or destroying crust.

Laurasia

The northern landmass formed when Pangaea broke apart about $200\,\text{million years}$ ago.

Gondwana

The southern landmass formed when Pangaea broke apart, which included Africa, South America, Antarctica, Australia, and India.

Glossopteris

A fossil seed fern found across southern continents (South America, Africa, India, Australia, New Zealand, Antarctica) that supports plate tectonics.

Fold

A bend in rock layers caused by slow, powerful tectonic compressive forces.

Anticline

An upward fold in rock layers shaped like an A.

Syncline

A downward fold in rock layers shaped like a V.

Fault

A break in Earth's crust along which movement of rocks can occur.

Compression

A tectonic force that pushes rocks together, producing reverse faults and folds.

Tension

A tectonic force that pulls rocks apart, producing normal faults, horsts, and grabens.

Shearing

A tectonic force that causes rocks to slide past each other in opposite directions, producing strike-slip faults.

Reverse fault

A fault produced by compression where one block of crust moves up relative to another.

Normal fault

A fault produced by tension where one block of crust moves down relative to another.

Strike-slip fault

A fault produced by shearing where rocks move horizontally past each other.

Graben

A sunken block of crust (rift valley) that has dropped down between normal faults due to tension.

Horst

A raised block of crust that remains higher between normal faults.

P-waves

Primary body waves that are the fastest seismic waves, moving with a push-pull compression motion through both solids and liquids.

S-waves

Secondary body waves that travel slower than P-waves with an up-and-down transverse motion and can only pass through solids.

Love waves

Slow surface waves (also called L-waves) that move the ground from side to side like a slithering snake.

Rayleigh waves

Slow surface waves that cause the ground to move in a rolling motion similar to ocean waves.

Seismograph

An instrument (also called a seismometer) that records movements and seismic waves in Earth's crust.

Richter scale

A scale ranging from $0$ to $10$ developed in $1935$ that measures earthquake magnitude, where each $1.0$ increase represents $30$ times more energy released.

Tsunami

A series of powerful ocean waves created when underwater faults move or ocean floors are displaced.

DART

Deep-ocean Assessment and Reporting of Tsunamis; an early warning system using ocean buoys to detect sea-level changes.

Volcano

A geological structure formed when molten rock beneath Earth's surface pushes through a weakness in the crust.

Magma

Molten rock located beneath Earth's surface.

Lava

Molten rock that reaches Earth's surface.

Volcanologist

A scientist who studies volcanoes.

Volcanic bomb

A large rock fragment thrown from the crater of a volcano during an eruption.

Hotspot

An area where extremely hot mantle rock rises and pushes magma upward through a plate, forming volcanic chains as the plate moves over it.

Black smoker

A seafloor vent at ocean ridges that releases superheated water containing dissolved elements.

Active volcano

A volcano that is currently erupting or has erupted recently.

Dormant volcano

A volcano that is not currently active but has erupted within the last $10\,000\,\text{years}$ and could erupt again.

Extinct volcano

A volcano that has not erupted for at least $10\,000\,\text{years}$ and is not expected to erupt again.

Natural hazard

A potentially harmful natural event.

Natural disaster

A natural hazard that causes major loss of life, property damage, or economic harm.

Seismoscope

A device invented by Zhang Heng in $132\,\text{AD}$ that detects the direction of earthquake movement without keeping a time record.

Liquefaction

A process during an earthquake where shaking causes solid ground to become soft and unstable.

Tiltmeter

A monitoring instrument that measures tiny changes in ground slope.

Strainmeter

A monitoring instrument that measures tiny changes in the shape of the ground.