Layers of Earth and Plate Tectonics - Vocabulary Flashcards

A set of vocabulary flashcards covering Earth’s layers, lithosphere, mantle, core, seismic waves, plate tectonics, volcanoes, and related concepts from the lecture notes.

Crust

The outermost solid shell of Earth, including continental and oceanic crust; thickness roughly 0–100 km at the surface.

Oceanic Crust

Thinner, more dense crust beneath the oceans, composed mainly of basalt.

Continental Crust

Thicker, less dense crust that floats higher than oceanic crust and is primarily granitic.

Mantle

Layer beneath the crust, divided into upper and lower mantle; lies between the crust and outer core.

Asthenosphere

Part of the upper mantle just below the lithosphere that is ductile and can flow, enabling plate movement.

Lithosphere

Rigid outer shell of Earth, comprising the crust and the upper mantle; about 80 km thick, varies by region.

Moho (Mohorovičić Discontinuity)

Boundary between the crust and the mantle.

Outer Core

Liquid iron–nickel layer surrounding the inner core; convection here generates Earth’s magnetic field.

Inner Core

Solid iron–nickel sphere at the center of Earth.

Plate Tectonics

Theory that Earth’s lithospheric plates move and interact, shaping volcanoes, mountains, and earthquakes.

Convection (Mantle)**

Heat-driven movement within the mantle that drives plate motion.

Lithosphere vs. Mantle distinction

Lithosphere is the rigid outer shell (crust + upper mantle); underlying mantle is the rigid but more ductile layer that enables movement.

Plate Boundaries

Locations where tectonic plates meet and interact; types include divergent, convergent, and transform.

P-Waves (Primary Waves)

Fastest seismic waves; travel through solids, liquids, and gases; compress and expand the material.

S-Waves (Secondary Waves)

Slower seismic waves; travel only through solids; cause shear motion perpendicular to travel direction.

Love Waves

Surface seismic waves that move ground side-to-side; often highly destructive.

Rayleigh Waves

Surface seismic waves that roll in an elliptical motion; can cause significant ground movement.

Seismograph

Instrument used to detect and record seismic waves, aiding epicenter location.

Epicenter

Point on Earth’s surface directly above the earthquake’s starting point.

Volcano

A vent or fissure through which magma erupts; can be active, dormant, or extinct.

Active Volcano

A volcano that has erupted recently or is likely to erupt again.

Dormant Volcano

A volcano that has not erupted for a long time but may erupt in the future.

Extinct Volcano

A volcano that is not expected to erupt again.

Volcanic Arc

A chain of volcanoes formed above a subducting plate, common around the Pacific Ring of Fire.

Volcanic Distribution

Volcanoes are mainly located along plate margins and subduction zones; may be active, dormant, or extinct.

Mountain Range

A series of mountains formed by plate movements (divergence or convergence).

Major Tectonic Plates

Seven large plates: North American, South American, Eurasian, Pacific, Indo-Australian, African, and Antarctic.

Intermediate/Minor Plates

Smaller plates such as Philippine, Caribbean, Cocos, Nazca, Juan de Fuca, Scotia, Arabian.

Pangaea

Hypothesized supercontinent that existed ~250 million years ago and began breaking apart.

Panthalassa

The global ocean that surrounded Pangaea.

Pacific Ring of Fire

A volcanic arc around the rim of the Pacific Ocean, driven by subduction and plate interactions.

Plate Movement

Plates move slowly and continuously along plate margins due to convection in the mantle.

Crust vs Mantle Relationship

Crust is the outermost layer; mantle lies beneath it; the lithosphere includes crust plus the upper mantle.

Evidence for Plate Tectonics (Wegener/Drift)**

Conceptual evidence from continental drift (Wegener) and studies of the ocean floor supporting plate movement.

Upper Mantle

Section of the mantle just below the crust and above the transition zone.

Lower Mantle

Portion of the mantle below the transition zone, extending toward the outer core.

Shallow Earthquakes

Earthquakes with depths 0–100 km.

Intermediate Earthquakes

Earthquakes with depths 100–300 km.

Deep Earthquakes

Earthquakes with depths greater than 300 km.

Divergent Plate Boundary

Plate margins where plates move apart, often with seafloor spreading.

Convergent Plate Boundary

Plate margins where plates come together, often forming mountains or subduction zones.

Transform Plate Boundary

Plate margins where plates slide past one another horizontally.