Plate Tectonics

These flashcards cover key terms and concepts related to plate tectonics, the structure of the Earth, and the geological processes involved.

Inner Core

The central part of the Earth, extending from a depth of about 5,150 km to the Earth’s center, composed primarily of solid iron.

Outer Core

A liquid layer of the Earth that extends from 2,900 km to about 5,150 km beneath the surface, mainly composed of liquid iron and nickel.

Mantle

The thickest layer of the Earth, making up around 75% of its volume, consisting primarily of silicate rocks rich in iron and magnesium.

Lithosphere

The rigid, outermost layer of the Earth, composed of the crust and the uppermost mantle.

Asthenosphere

The semi-molten part of the mantle that acts as a lubricant for the lithosphere to slide on.

Crust

The solid outer layer of the Earth that lies on top of the lithosphere.

Oceanic Crust

Much thinner crust beneath the oceans, averaging 8 km in thickness, composed mainly of heavier rocks like basalt.

Continental Crust

Thicker crust beneath continents, typically 45 km, composed mainly of lighter rocks like granite.

Plate Tectonics

The theory that explains how the Earth's plates move and interact, resulting in geological phenomena such as earthquakes and volcanoes.

Subduction

A process occurring at convergent boundaries where one plate sinks under another, usually the oceanic plate under the continental plate.

Divergent Plate Boundary

A constructive plate boundary where two plates move away from each other, allowing magma to rise and create new land.

Transformative Plate Boundary

A boundary where two plates slide past one another, characterized by friction that can cause earthquakes.

Continental Drift

The theory proposed by Alfred Wegener that continents are constantly moving and were once joined as a supercontinent called Pangea.

Convection Currents

The movement of magma resulting from heating and cooling that drives the movement of tectonic plates.

Mid-Atlantic Ridge

A geological feature formed by seafloor spreading, where tectonic plates separate, resulting in new land formation.

Folds

Bends in rock layers that occur due to compression when two tectonic plates collide.

Caledonian Orogeny

The mountain-building event that formed the mountains of Northern Ireland and parts of Eastern Canada.

Armorican Orogeny

The mountain-building event caused by the collision of the Eurasian and African plates, affecting southern Ireland.

Lithification

The process by which sediments are compacted and cemented to form sedimentary rocks.

Seafloor Spreading

The process of new oceanic crust forming at mid-ocean ridges as tectonic plates move apart.