California Geology Concepts Study Guide

Comprehensive vocabulary flashcards covering Earth structure, plate tectonics, seismic wave propagation, mineral properties, rock types, metamorphic grades, and geochronological concepts.

Seismic

Relating to, caused by, or subject to an earthquake or other earth vibrations.

P wave

A primary body wave that arrives first and can travel through both solid and liquid material.

S wave

A secondary body wave that comes after a P wave and can only travel through solid material.

Body wave

Earthquake vibrations, specifically P waves and S waves, that travel through the interior of the Earth.

Focus (earthquake location)

The exact location under the surface or crust of the Earth where an earthquake initially hits.

Accretion

A gradual increase, growth, or buildup of size, mass, or layers through a slow, natural accumulation of materials, such as in an accretionary wedge.

Differentiation

The separation of a mixed planetary material into two distinct geological reservoirs.

Chondrite

A type of stony meteorite that has never been melted, containing small, rounded mineral grains called chondrules.

Siderophile

Elements that have a strong chemical affinity for iron ("love iron").

Lithophile

Elements that have a strong chemical affinity for rocks ("love rocks").

Moho

The compositional boundary and mineral transition separating the Earth's mantle from the crust.

Piercing point

A geologic feature or rock body cut and potentially offset or moved by a fault.

Pangaea

The supercontinent where all continental masses were originally joined together before being split apart by plate tectonics.

Spreading center

A divergent plate boundary that splits apart and generates new rock from solidifying magma.

Magma

Molten rock that flows beneath the crust of the Earth.

Subduction zone

A convergent boundary where a denser tectonic plate plunges beneath a less dense plate, typically creating a volcanic arc.

Tectonic plate

A large, solid slab of rock composed of both oceanic and continental lithosphere.

Inner core

A solid ball of metal at Earth's center composed of an iron-nickel alloy that is neither brittle nor ductile.

Outer core

A liquid layer composed of iron and nickel that is neither brittle nor ductile.

Mantle

A mostly solid planetary layer rich in iron and magnesium silicate rock, comprising an upper and lower mantle, exhibiting both brittle and ductile behavior.

Crust

The outermost solid rocky layer of Earth composed of silicate minerals, separated from the underlying mantle by the Moho.

Lithosphere

The rigid, brittle, solid outer layer of the Earth consisting of the crust and uppermost solid mantle.

Aesthenosphere

The weak, ductile, semi-fluid layer of Earth's upper mantle situated directly beneath the rigid lithosphere.

Slab pull

A gravitational force in subduction zones where a cold, dense plate is pulled downward into the mantle beneath a less dense plate.

Ridge push

A gravitational driving force at spreading ridges that pushes tectonic plates apart as magma ascends to the surface and cools into solid rock.

Seafloor magnetic anomalies

Symmetrical patterns of alternating magnetic stripes preserved in oceanic crust, formed by seafloor spreading in tandem with periodic magnetic field reversals.

Mineral

A naturally occurring solid formed by geologic processes, characterized by a well-defined crystal structure and a fairly well-defined chemical composition.

Crystal lattice

The three-dimensional, repeating geometric arrangement of atoms, ions, or molecules within a crystalline solid.

Amorphous

The condition of a mineral or solid that lacks an ordered crystalline structure, such as natural glass.

Polymorph

A mineral that shares the exact same chemical composition as another mineral but features a different internal crystal structure.

Solid solution

A condition where two or more elements or ions randomly substitute for each other within a mineral's crystal structure without changing that structure.

Complete solid solution

A solid solution where two endmember components mix in a solid state to form a single homogeneous crystal lattice across all possible concentrations.

Incomplete solid solution

A solid solution where a solute dissolves into a solvent crystal lattice only up to a specific concentration limit rather than mixing completely in all proportions.

Olivine

A common green magnesium-iron silicate abundant in low-silica mafic and ultramafic igneous rocks, believed to be the most abundant mineral of Earth's upper mantle.

Silicate

Chemical compounds composed fundamentally of silicon, oxygen, and various metals.

Igneous rock

Rock formed through the cooling and solidification of rock that has melted within the Earth.

Sedimentary rock

Rock created by the accumulation and consolidation of materials layered on top of each other over time.

Metamorphic rock

Rock altered from preexisting parent rock through the direct application of intense heat and pressure.

Metamorphic facies

A set of distinct mineral assemblages in metamorphic rocks that form under predictable, similar ranges of pressure and temperature.

Metamorphic grade

A measure of the intensity of temperature and pressure experienced by a rock during metamorphism, indicating how much it has changed from its protolith.

Geothermal gradient (Geotherm)

The rate at which Earth's temperature increases with increasing depth toward the core, often plotted as a depth-temperature curve.

Foliation

Any repetitive, penetrative planar fabric or layered structural alignment found in metamorphic rocks.

Phyllite

A fine- to medium-grained foliated metamorphic rock.

Schist

A medium-grade metamorphic rock characterized by visible, platy mineral grains that impart a scaly, sparkly, and layered appearance.

Gneiss

A high-grade, coarse-grained metamorphic rock defined by alternating light and dark mineral bands.

Radiometric dating

A geochronological method that determines the age of rocks, minerals, or organic materials using the ratio of unstable parent isotopes to stable daughter isotopes.

Uranium-lead dating

A specific radiometric dating technique based on the radioactive decay chain from uranium to lead used to date geological materials.

Stable isotope

Non-radioactive forms of chemical elements that possess identical proton counts but varying neutron counts, which do not undergo radioactive decay.

Radiogenic isotope

An isotope that is produced directly by the radioactive decay of an unstable parent isotope.

Half life

The specific amount of time required for an unstable substance or parent isotope to decay to half of its initial quantity.

Closed system

A system in which only energy can transfer in and out, while matter remains contained.

Concordia

A reference curve used in uranium-lead dating diagrams to distinguish concordant isotopic systems from those that have experienced lead loss.

Discordant

A geological arrangement occurring when alternating bands of different rock types run perpendicular or at an angle to the coast or landscape feature.

Craton

An ancient, stable part of continental crust and lithospheric mantle that has survived without experiencing significant deformation.