Plate Tectonics and Earth’s Structure

Vocabulary flashcards covering Earth’s layers, plate tectonics, continental drift, and seafloor spreading concepts from the lecture notes.

Plate Tectonics

The theory that Earth’s outer shell is divided into moving plates of varying size and thickness.

Tectonic Plate

A rigid segment of the lithosphere that moves over the mantle, carrying continents and oceans with it.

Lithosphere

The crust plus the rigid upper mantle; it is broken into tectonic plates.

Continental Crust

The thicker part of Earth’s crust located under landmasses rather than oceans.

Oceanic Crust

The thinner part of Earth’s crust found beneath the oceans.

Upper Mantle

The thick, rocky part of the mantle directly below the crust.

Lower Mantle

The semi-solid, plastic-like rock layer beneath the upper mantle.

Mantle

A rocky layer under the crust composed of silicon, oxygen, magnesium, iron, aluminum, and calcium; convection currents move heat through it.

Convection Currents (Mantle)

Heat-driven circulation in the mantle that transfers heat from the hot inner mantle toward the cooler outer mantle.

Outer Core

A molten iron-nickel layer that surrounds the solid inner core.

Inner Core

Earth’s solid, extremely hot iron-nickel center under immense pressure.

Core

Earth’s innermost layer composed of a liquid outer portion and a solid inner portion.

Continental Drift

Early 1900s idea that continents move across Earth’s surface and were once joined as a single landmass.

Pangaea

The supercontinent proposed by Wegener in which all present continents were once joined together.

Seafloor Spreading

Process in which molten rock rises at mid-ocean ridges, forms new oceanic crust, and pushes plates apart.

Rift Valley (Mid-Ocean)

The split at the crest of an underwater ridge where magma breaks through during seafloor spreading.

Mid-Ocean Ridge System

A global chain of underwater mountains where the youngest oceanic rocks are found.

Subduction Zone

A plate boundary where one tectonic plate slides beneath another, illustrated by triangles pointing in the direction of subduction.

Continents

The seven large landmasses—Africa, Antarctica, Asia, Europe, North America, South America, and Australia.

Oceans

The five major bodies of salt water—Pacific, Atlantic, Indian, Arctic, and Southern—covering more than 70 % of Earth’s surface.

Landforms

Natural surface features such as mountains, hills, plateaus, and plains.

Crust

Earth’s rigid, rocky outer surface composed mainly of basalt and granite; thinner under oceans.

Plate Motion Effects

Volcanoes, earthquakes, mountain ranges, and islands result from the movement of tectonic plates.

Earth’s Layers

From outside to inside: crust, mantle, outer core, and inner core.