Introduction to Geology: Comprehensive Student Review

Vocabulary-based flashcards covering introductory geology, planetary formation, plate tectonics, mineralogy, petrology, and historical dating methods.

Geology

The study of the earth and extra terrestrial bodies, derived from the words "Geo" (Earth) and "logos" (discourse).

Physical Geology

A main branch of geology that deals with rocks, minerals, and the physical processes that occur around them.

Historical Geology

A main branch of geology focused on the origins and evolution of Earth through time.

Catastrophism

A school of thought from the $16th-17th$ Century which suggested that sudden, worldwide catastrophes changed the earth's physical features.

Uniformitarianism

The principle that physical, chemical, and biological processes operating today also operated in the past, summarized by the phrase "present is the key to the past."

Actualism

The modern belief that present processes can explain the past, though not necessarily at the same rate, intensities, or conditions.

Singularity

An infinitely small region of zero volume and no dimensions from which the entire universe is said to have originated.

Big Bang Theory

Proposed by Georges Lemaitre in the $1920s$, it states the universe expanded from an initial state of extremely high density and temperature.

Epoch of Recombination

A phase in the early universe occurring approximately $300,000$ years after the Big Bang when light first began to appear.

Hubble's Law

The observation that galaxies move away from each other at a distance proportional to their distance, leading to a redshift in the light spectrum.

Cosmic Microwave Background Radiation

The relic electromagnetic radiation or "afterglow" from the Epoch of Recombination, currently measuring approximately $2.725$ Kelvin.

Big Bang Nucleosynthesis

The formation of the primordial elements hydrogen ($H$), helium ($He$), and trace amounts of beryllium ($Be$) and lithium ($Li$).

Nebular Hypothesis

The theory that the solar system formed approximately $4.571$ BYA from a giant rotating cloud of gas and dust.

Stellar Nucleosynthesis

The process of nuclear fusion within stars where hydrogen and helium are converted into heavier elements up to iron ($Fe$) and nickel ($Ni$).

Planetesimals

Kilometer-sized building blocks formed from the protoplanetary disk that eventually coalesce to become planetary embryos.

Frost Line

The specific distance from the Sun cold enough for volatiles like water and ammonia to condense into solid ice.

Iron Catastrophe

The differentiation process where heavy siderophile metals like $Fe$ and $Ni$ sank to the center to form the core, while lithophiles rose to form the mantle and crust.

Giant Impact Hypothesis

The theory that a collision between proto-earth and a planetesimal named Theia around $4.5$ BYA resulted in the formation of the Moon.

Great Oxidation Event

A significant rise in atmospheric oxygen around $2.4$ BYA caused by cyanobacteria, leading to the mass extinction of anaerobic bacteria.

Radiometric Dating

A technique used to measure the abundance of radioactive isotopes to determine the age of Earth's materials based on half-life and decay.

Mohorvicic Discontinuity

The boundary layer located between the Earth's crust and the mantle.

Asthenosphere

A weak, viscous, and ductile layer of the mantle that allows for the movement of the overlying lithosphere.

Gutenberg Discontinuity

The boundary layer located between the Earth's mantle and the outer core.

Lehmann Discontinuity

The boundary layer found between the Earth's liquid outer core and the solid inner core.

Isostasy

The principle of gravitational equilibrium where the low-density crust floats above the high-density mantle rocks.

Orogenesis

The geological process of mountain building.

Continental Drift Hypothesis

Proposed by Alfred Wegener, suggesting that the continents move laterally and were once joined in a supercontinent called Pangaea.

Panthalassa

The massive super-ocean that surrounded the supercontinent Pangaea.

Seafloor Spreading

The process proposed by Harry Hess where the seafloor moves laterally away from mid-ocean ridges due to mantle upwelling.

Curie Point

The specific temperature at which a material loses its permanent magnetism.

Wilson Cycles

The geological cycle involving the opening and closing of ocean basins over time.

Mineral

A naturally occurring, inorganic, homogenous solid with a definite chemical composition and an ordered internal structure.

Polymorphism

The ability of a chemical substance to exist in multiple forms or crystal structures, such as diamond and graphite.

Cleavage

The tendency of a mineral to break along planes of weak atomic bonds.

Silicon Tetrahedron

The basic building block of rock-forming silicate minerals, represented as $SiO_4^{4-}$.

Anatexis

The process of partial melting of the mantle that leads to the generation of magma.

Geothermal Gradient

The natural increase in temperature with depth below the Earth's surface, averaging $25-30$ $^{\circ}C/km$.

Flux Melting

A process occurring in subduction zones where the addition of volatiles like water lowers the melting temperature of rocks.

Bowen Reaction Sequence

A model describing the sequence in which minerals crystallize from a cooling magma melt.

Phaneritic

An igneous rock texture featuring visible, coarse-grained crystals formed by the slow cooling of magma underground.

Aphanitic

A fine-grained igneous rock texture where crystals are microscopic, resulting from rapid cooling at the surface.

Pyroclastic Density Currents (PDCs)

High-velocity avalanches of hot gases and volcanic ash that are the deadliest volcanic hazards.

Metamorphism

The transformation of a parent rock (protolith) into a new form due to heat, pressure, and chemically active fluids without melting.

Metasomatism

A metamorphic process involving the exchange of ions through hydrothermal solutions that changes the chemical composition of a rock.

Foliation

The planar arrangement of mineral grains or crystals in a metamorphic rock, often caused by directed compression.

Goldich Stability Series

A method of predicting weathering potential where minerals formed at higher temperatures are generally more susceptible to chemical weathering.

Lithification

The transformation of loose sediments into solid sedimentary rock through compaction and cementation.

Diagenesis

The collective physical, chemical, and biological processes that affect sediments after deposition but before metamorphism.

Unconformity

A gap in the rock record representing a period of erosion or non-deposition.

Milankovitch Cycles

Periodic variations in Earth's orbit and axial tilt, including eccentricity, precession, and obliquity, that influence long-term climate.