Geology, Plate Tectonics, Seismology, and Volcanism

Vocabulary flashcards covering core geological concepts, historical figures, plate tectonics, seismic phenomena, and volcanology.

Henri Bequerel

Scientist who discovered that some atoms break down in a predictable fashion known as radioactivity.

Alfred Wegener

Scientist who proposed the theory of continental drift, supported by the jigsaw fit of continents, glacial terrain fit, fossil stratigraphy, and the supercontinent Pangea.

Elastic deformation

Deformation occurring at low applications of stress where the rock changes shape temporarily but returns to its original shape when the stress is released.

Focus

The point beneath Earth's surface where rock breaks under stress and causes an earthquake.

Epicenter

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

Nuée ardente

A fast-moving, dense cloud of hot pyroclastic materials and gases ejected from a volcano.

Repose

The period of time between volcanic eruptions.

Fractional crystallization

The process where mineral crystals form in cooling melt; crystals heavier (higher specific gravity) than the melt fall toward the base of the magma chamber, forming rocks composed almost entirely of these minerals.

Ultra-low Velocity Zone (ULVZ)

A discontinuous zone at the core-mantle boundary characterized by large reservoirs of magma where seismic waves slow down; associated with plumes and hot spots.

Nicolaus Steno

Scientist recognized as the father of stratigraphy; proposed fundamental geological principles based on the idea that sedimentary layers are deposited flat over wide areas, with older layers at the base.

Thomas Burnet

Geological thinker who believed in the literal biblical translation of creation and assumed Earth's uneven surface features were caused by the global flood.

Archbishop Ussher

Cleric who calculated from biblical birth and death records that Earth was created at sunset on October 22nd, 4004 BC.

Catastrophism

An attempt to recognize geological processes while confining them to biblical chronology; posited that Earth's history consists of unique, unpredictable catastrophic events without natural evolution.

Baron Cuvier

Naturalist who recognized repeated series of sediment layers and interpreted them as evidence of successive flood stages tied to Noah's Ark.

James Hutton

Considered the father of modern geology; introduced the concept of gradualism, discovered and defined unconformities, and disregarded religious dates while remaining a deist.

Leonardo da Vinci

The first thinker noted for recognizing the basic concept of uniformitarianism, though he did not name or develop it.

Charles Lyell

Geologist who authored the influential book 'Principles of Geology'.

Angular unconformity

A type of unconformity where the rock beds lying above and below the erosional boundary have different slopes or angles.

Disconformity

A type of unconformity where sedimentary beds above and below the erosional surface remain parallel, but represent a gap in time.

Non-conformity

A type of unconformity where sedimentary layers lie over or are intruded by igneous or crystalline rocks.

Hugo Benioff

Geophysicist who developed and applied seismographs to accurately determine earthquake locations.

Dynamo model

The model explaining planetary magnetic fields as generated by electric currents moving within a molten iron core.

Rayleigh waves

Surface seismic waves that cause the ground to move in an up-and-down, rolling motion.

Richter magnitude scale

An early earthquake scale based on distance and amplitude that is not valid for magnitudes above 8.

Seismic gap

An area along an active fault that has not experienced earthquake activity for a prolonged period, used to forecast future earthquakes.

Assimilation

The process by which ascending hot magma penetrates fractures, loosens blocks of host rock, and melts them into the magma.

Unconformity

A geological horizon representing a time break where erosion took place before newer strata were deposited.

William Smith

The first person to identify matching strata across different parts of a country by analyzing their fossil content.

Eras

Long intervals of geologic time.

Isotope

Atoms of the same element that have the same number of protons but differ in their number of neutrons.

Half-life

The period of time required for half of the radioactive parent nuclei in a sample to decay into daughter products.

Harry Hes

Geologist who discovered that mid-ocean ridges represent spreading centers where new ocean floor is built and crust moves outward in opposite directions.

Vine and Matthews

Researchers who studied Earth's magnetic reversals through the analysis of basalt strips and rock magnetism.

Paleomagnetism

The study of Earth's magnetic field through history via the analysis of magnetic minerals preserved in rocks.

Subduction zones

Convergent plate boundaries where oceanic plates are pushed downward into the upper mantle and destroyed.

Seismic tomography

An imaging method that detects cooler ocean floor slabs as they sink toward the core-mantle boundary.

Aulacogen

A failed rift arm of a triple junction rift system in plate tectonics.

Stress

The force or energy imposed on a body of rock.

Strain

A change in the shape or volume of rock caused by stress.

Ductile deformation

Permanent change in the shape of a rock that remains even after the applied stress is released.

P waves

Compressional primary seismic waves that compress and expand the ground, capable of traveling through all states of matter.

S waves

Secondary shear seismic waves that displace the ground up and down or side to side.

Love waves

Surface seismic waves that move horizontally across the surface like a slithering snake.

Inertia

The tendency of an object to resist a change in motion, providing a brief delay before vibrations move large masses during an earthquake.

Modified Mercalli intensity scale

A subjective scale used to evaluate earthquake damage and shaking intensity felt by observers.

Moment magnitude scale

An earthquake scale calculated from total released energy, determined by fault rupture area, offset amount, and rock strength.

Paleoseismology

The study of prehistoric earthquakes, dating seismic events that occurred up to 50,000 years ago.

Megathrust earthquake

A massive earthquake occurring along the broad interface boundary zone between a subducting plate and an overriding plate.

Tsunami

A series of large ocean waves radiating outward from a point of sudden, large vertical displacement of water.

Run-up

The maximum vertical height of a tsunami wave reaching onto land above sea level.

Imamura-Iida scale

A tsunami magnitude scale calculated as a function of the maximum wave height measured in the open ocean.

Draw down

The noticeable receding of seawater at the coastline immediately preceding the arrival of a tsunami wave.

Hazard maps

Cartographic tools used for regional land-use decisions, such as siting hospitals, schools, homes, and nuclear power plants safely.

MORB

Mid-ocean ridge basalt.

Peridotite

Mantle rock located in the asthenosphere that undergoes partial melting to yield basaltic magma.

Viscosity

A fluid's resistance to flow, determined by factors such as temperature, dissolved volatile content, silica content, and crystal proportion.

Ring of Fire

A prominent belt of active volcanoes grouped along convergent plate boundaries around the Pacific Ocean.

Plutonic rocks

Igneous rocks produced by magma cooling and solidifying beneath Earth's surface.

Pahoehoe

Basaltic lava characterized by a smooth, billowy, or ropy surface texture.

Andesite

Intermediate volcanic rock formed through moderate magmatic modification.

Rhyolite

Felsic volcanic rock with high silica and volatile content formed from extensive modification of magma.

Magma chamber

A subsurface reservoir beneath a volcano where molten rock accumulates prior to an eruption.

Magma mixing

The interaction that occurs when an incoming bleb of basaltic magma blends with a modified magma pool already situated in a magma chamber.

Giant resurgent calderas

Massive collapse features that form over continental mantle plumes due to the regional evacuation and collapse of extensive magma chambers.

Plinian eruption

An explosive volcanic eruption where gas and tephra flow straight out through the top of the volcano.

Pelean eruption

A volcanic eruption characterized by explosive lateral blasts erupting out the side of the volcano.

Volcanic Explosivity Index (VEI)

A relative scale measuring volcanic eruption explosiveness, where each successive integer indicates a ten-fold increase in eruptive power.

Aerosols

Microscopic droplets of acid formed in the atmosphere from volcanic gas emissions.