Plate Tectonics and Seismology Lecture Notes

These vocabulary flashcards cover early and modern geological theories, the internal structure of the Earth, plate boundary evidence, and the mechanics and measurement of earthquakes.

Geology

The study of the Earth’s structure, the rocks it is composed of, and the processes by which it changes.

Static Earth Theory

An early theory suggesting that Earth and its continents have changed through periodic expansion and contraction, which caused earthquakes and volcanoes.

Catastrophism

The idea that violent geological upheavals, such as volcanoes and floods, were the main driving force for past change on Earth.

Uniformitarianism

A theory proposed by James Hutton stating that geological processes happening today have been the same throughout Earth's history, summarized as "the present is the key to the past."

Law of Superposition

A principle used by Charles Lyell stating that younger layers of sediments rest on top of older layers.

Continental Drift

A theory proposed by Alfred Wegener in the 1900s suggesting that Earth's continents move across the ocean over time and were once joined together.

Pangaea

The name of the supercontinent where all of Earth's continents were once joined together according to Alfred Wegener.

Plate Tectonics Theory

The modern theory replacing continental drift which states the Earth’s crust consists of giant tectonic plates moved by convection currents in the molten magma.

Crust

The outermost layer of rock on the Earth.

Asthenosphere

The mobile upper portion of the Earth's mantle.

Mesosphere

The rigid lower layer of the Earth's mantle.

Outer Core

The liquid layer of the Earth composed of nickel and iron.

Inner Core

The solid ball of iron located at the center of the Earth.

Convection

The process where hotter, less dense material in the lower mantle moves upward while cooler, more dense material moves downward; it is the main driving force for plate movement.

Subduction

A process occurring when a more dense tectonic plate collides with a less dense plate and is forced down into the mantle.

Mid-ocean Ridges

Underwater mountain ranges formed where oceanic tectonic plates spread apart due to pressure from mantle convection.

Paleomagnetism

The study of the alignment of magnetic particles in rocks, which reveals that Earth's magnetic field direction has reversed many times in the past.

Earthquake

An event during which the ground shakes, often caused by the sudden movement of tectonic plates.

Fault

The point within Earth where tectonic plates move against each other and where earthquakes are most likely to occur.

Focus

The location within the Earth where energy is released and serves as the source of seismic waves.

Epicenter

The location on Earth’s surface directly above an earthquake focus.

Body Waves

Seismic waves that move through Earth's interior, categorized as Primary (P) waves and Secondary (S) waves.

Primary (P) Waves

Longitudinal body waves that travel fastest, arrive first, and can travel through both solids and liquids.

Secondary (S) Waves

Transverse body waves that travel slower than P waves, arrive second, and can travel through solids but not liquids.

Surface Waves

Seismic waves that move across the Earth’s surface, categorized as Love (L) waves and Rayleigh (R) waves.

Love (L) Waves

Surface waves that exhibit side-to-side motion.

Rayleigh (R) Waves

Surface waves that exhibit a rolling motion similar to an ocean wave.

Seismometer

An instrument that detects and records seismic waves.

Triangulation

A method using three seismograph stations to locate the epicenter of an earthquake by finding the intersection of circles representing distance.

Amplitude

The maximum displacement that occurs during a vibration, used to calculate an earthquake’s magnitude.

Richter Scale

A base-ten logarithmic scale where each whole-number increase represents a $10$ times increase in ground motion and approximately $30$ times more energy release.

S-wave Shadow

An area on the side of Earth opposite to a seismic source where S-waves do not appear, proving that the Earth's outer core is liquid.