GEOL 1006: The Earth's Interior and Surface Processes

Comprehensive vocabulary review flashcards covering historical and physical geology, minerals, the rock cycle, igneous processes and rocks, volcanism, and weathering processes.

Physical Geology

The division of geology that examines the materials composing Earth and seeks to understand the processes that operate beneath and upon its surface.

Historical Geology

The branch of geology that aims to understand the origin of Earth and its development through time by establishing an orderly chronological arrangement of past physical and biological changes.

Catastrophism

The doctrine dominant in the 17th and 18th centuries stating that Earth's landscapes and features were shaped primarily by sudden, worldwide catastrophes.

Uniformitarianism

The fundamental geological principle proposed by James Hutton in 1788 stating that the physical, chemical, and biological laws that operate today have also operated in the geological past, summarized as 'the present is the key to the past.'

Law of Superposition

The relative dating principle stating that in an undisturbed sequence of sedimentary rocks or surface deposits, the oldest layers are at the bottom and the youngest are on top.

Principle of Fossil Succession

The principle stating that fossil organisms succeed one another in a definite and determinable order, allowing any time period to be recognized by its fossil content.

Nebular Theory

The scientific explanation proposing that our solar system evolved approximately $5\text{ billion years ago}$ from the gravitational collapse of a rotating interstellar cloud composed mostly of hydrogen and helium.

Continental Drift

The hypothesis proposed by Alfred Wegener in 1915 suggesting that all continents were once assembled into a single supercontinent that later broke apart and drifted to their current positions.

Pangaea

The proposed supercontinent that began breaking apart approximately $200\text{ million years ago}$ into smaller continental masses.

Glossopteris

A late Paleozoic fossil fern with large seeds incapable of long-distance transport, whose widespread discovery across Africa, Australia, India, South America, and Antarctica supported Wegener's continental drift hypothesis.

Mesosaurus

A small, aquatic, fish-eating reptile from the late Paleozoic found exclusively in South America and southern Africa, providing paleontological evidence that the continents were once joined.

Oceanic Crust

Earth's basaltic outer layer averaging $7\text{ km}$ in thickness, with an average density of approximately $3.0\text{ g/cm}^3$, consisting of rocks typically aged $180\text{ million years}$ or less.

Continental Crust

Earth's outer rock layer averaging $35\text{ km}$ thick (reaching up to $70\text{ km}$ in mountainous regions), with an average density of approximately $2.7\text{ g/cm}^3$ and a composition grading from granitic rocks near the surface to basaltic rocks at depth.

Mantle

A solid, ductile rocky shell extending to a depth of approximately $2,900\text{ km}$ and comprising $82\%$ of Earth's volume, dominantly composed of the ultramafic rock peridotite with an average density around $3.3\text{ g/cm}^3$.

Earth's Core

Earth's dense innermost layer composed primarily of an iron-nickel alloy with minor amounts of oxygen, silicon, and sulfur, exhibiting densities ranging from $11\text{ g/cm}^3$ to $14\text{ g/cm}^3$.

Lithosphere

Earth's relatively cool, rigid, and brittle outer mechanical shell comprising the crust and uppermost mantle, averaging $100\text{ km}$ in thickness (ranging from $5\text{ km}$ to $250\text{ km}$).

Asthenosphere

A soft, weak mechanical layer in the upper mantle beneath the lithosphere, extending to roughly $410\text{ km}$ depth, where high temperatures promote minor partial melting that allows overlying tectonic plates to move independently.

Mesosphere (Lower Mantle)

The solid, rigid mantle zone situated between $410\text{ km}$ and $2,900\text{ km}$ depth, where extreme confining pressures counteract heat effects to gradually increase mechanical rock strength downward.

Outer Core

A liquid layer of iron-nickel alloy approximately $2,270\text{ km}$ thick whose convective currents generate Earth's magnetic field.

Inner Core

A solid metallic sphere at Earth's center with a radius of $1,216\text{ km}$, maintained in a solid crystalline state by intense confining pressure.

Divergent Boundary

A plate boundary where tectonic plates pull apart, causing hot mantle material to upwell, melt, and generate new oceanic crust along oceanic ridges through seafloor spreading.

Convergent Boundary

A plate boundary where two lithospheric plates move together, leading to subduction (consumption of oceanic lithosphere into the mantle) or continental collision and mountain building.

Transform Boundary

A plate boundary where plates grind past one another horizontally along faults without creating or destroying lithosphere.

Rock Cycle

The continuous geological framework illustrating how internal and external Earth processes transform materials between igneous, sedimentary, and metamorphic rock types.

Mineral

Any naturally occurring, inorganic solid that possesses an orderly internal crystalline structure and a definite chemical composition.

Rock

Any solid mass of mineral or mineral-like matter that occurs naturally as an aggregate of minerals or non-mineral materials as part of Earth.

Ionic Bond

A chemical bond formed when one or more valence electrons are transferred between atoms, producing positively charged cations and negatively charged anions that attract one another into an electrically neutral crystal lattice.

Covalent Bond

A chemical bond formed by the sharing of electron pairs between adjacent atoms, producing strong, durable, and chemically inert structures.

Polymorph

Minerals that share identical chemical compositions but possess entirely different internal crystalline structures and physical characteristics due to different conditions of formation (e.g., diamond and graphite).

Crystal Habit

The external shape or geometric expression of a mineral that reflects its orderly internal arrangement of atoms when allowed to grow unconstrained.

Lustre

The appearance or quality of light reflected from the surface of a mineral, broadly categorized into metallic, sub-metallic, and non-metallic (such as vitreous, pearly, silky, resinous, or earthy).

Streak

The colour of a mineral in its finely powdered form, typically obtained by rubbing it across an unglazed porcelain plate, providing a more reliable diagnostic property than overall crystal colour.

Hardness

A mineral's resistance to scratching or abrasion, quantified numerically relative to reference minerals on the Mohs scale.

Cleavage

The tendency of a mineral to break cleanly along predictable planes of weak atomic bonding, producing characteristic smooth surfaces.

Conchoidal Fracture

A smooth, curved, shell-like breaking pattern exhibited by minerals and rocks (such as quartz and obsidian) that lack internal planes of weakness.

Specific Gravity

A dimensionless number representing the ratio of a mineral's weight to the weight of an equal volume of pure water at $4\,^{\circ}\text{C}$.

Silicon-Oxygen Tetrahedron

The fundamental anionic complex building block of all silicate minerals, consisting of four oxygen ions ($O^{2-}$) covalently bonded around a central silicon ion ($Si^{4+}$), represented by the formula $(\text{SiO}_4)^{4-}$.

Polymerization

The process by which silica tetrahedra link together by sharing one, two, three, or all four of their corner oxygen atoms to form single chains, double chains, sheets, or three-dimensional frameworks.

Ferromagnesian Silicates

Dark-coloured silicate minerals containing substantial iron ($Fe^{2+}$) or magnesium ($Mg^{2+}$) cations in their crystalline structure, characterized by higher specific gravities ($3.2$ to $3.6$).

Olivine

A high-temperature, dark olive-green ferromagnesian silicate group consisting of isolated tetrahedra linked by iron and magnesium ions, displaying conchoidal fracture and forming a dominant component of the upper mantle.

Pyroxene

A group of complex ferromagnesian silicate minerals (such as augite) structured as single chains of silica tetrahedra that exhibit two cleavage planes intersecting at approximately $90^{\circ}$.

Amphibole

A group of dark ferromagnesian silicates (commonly hornblende) composed of double chains of silica tetrahedra that produce two cleavage directions intersecting at $60^{\circ}$ and $120^{\circ}$.

Biotite

A dark, iron-rich sheet silicate belonging to the mica family that exhibits excellent cleavage in one direction, yielding shiny, flexible sheets.

Non-ferromagnesian Silicates

Silicate minerals that lack abundant iron and magnesium and are typically light in colour, lower in density (specific gravity averaging $\sim 2.7$), and enriched in aluminum, potassium, calcium, and sodium.

Muscovite

A light-coloured, pearly silicate mineral of the mica group with a sheet structure that provides excellent cleavage in one direction, commonly appearing clear to translucent.

Feldspar

The most abundant mineral group in Earth's crust, characterized by a three-dimensional framework structure with two planes of cleavage at or near $90^{\circ}$, subdivided into potassium feldspar and plagioclase feldspar.

Quartz

A hard, chemically resistant three-dimensional network silicate composed entirely of silicon and oxygen ($\text{SiO}_2$), bound by strong covalent bonds and lacking cleavage.

Magma

Completely or partially molten rock generated by the partial melting of Earth's mantle or crust, consisting of a liquid silicate melt, crystallized mineral solids, and dissolved volatiles.

Lava

Molten rock that reaches and extrudes onto Earth's surface, where loss of volatiles and cooling occur.

Geothermal Gradient

The gradual increase in temperature with increasing depth beneath Earth's surface, averaging roughly $25\,^{\circ}\text{C/km}$ in the upper crust.

Decompression Melting

The process of magma generation triggered when ascending mantle rock moves upward to lower confining pressures without losing substantial heat, causing its melting point to drop below its actual temperature.

Felsic (Granitic) Composition

Igneous rock composition enriched in light-coloured silicates (quartz and potassium feldspar), typically containing $65\%$ to $75\%$ silica ($\text{SiO}_2$) by weight and less than $10\%$ dark minerals.

Mafic (Basaltic) Composition

Igneous rock composition containing abundant dark ferromagnesian silicates and calcium-rich plagioclase feldspar, typically containing $45\%$ to $55\%$ silica ($\text{SiO}_2$) by weight.

Bowen's Reaction Series

A systematic sequence describing the predictable temperatures and orders at which specific silicate minerals crystallize from a cooling basaltic magma, or melt during heating.

Crystal Settling

A magmatic differentiation mechanism wherein early formed, dense minerals sink to the base of a magma chamber, chemically segregating crystals from the remaining liquid.

Assimilation

The magmatic process in which ascending magma incorporates and melts surrounding host rock, thereby altering the bulk chemical composition of the melt.

Aphanitic Texture

A fine-grained igneous rock texture formed by rapid cooling at or near Earth's surface, in which mineral crystals are too small to be identified without microscopic aid.

Phaneritic Texture

A coarse-grained igneous texture developed deep underground by slow cooling, characterized by intergrown mineral crystals that are roughly equal in size and visible to the unaided eye.

Porphyritic Texture

An igneous rock texture featuring two distinct crystal sizes, consisting of large isolated crystals (phenocrysts) set within a fine-grained or glassy groundmass, reflecting a multi-stage cooling history.

Glassy Texture

An amorphous igneous texture produced when extremely rapid quenching or high silica viscosity prevents ions from arranging into an orderly crystalline lattice, forming volcanic glass.

Pegmatite

An exceptionally coarse-grained igneous rock composed of interlocking crystals greater than $1\text{ cm}$ in diameter, formed during the final, volatile-rich stages of magma crystallization.

Granite

A phaneritic, felsic intrusive igneous rock composed predominantly of quartz (about $20\%$) and potassium/sodium feldspar (about $65\%$), with minor amounts of muscovite, biotite, or amphibole.

Rhyolite

A fine-grained (aphanitic), felsic extrusive igneous rock that is the volcanic compositional equivalent of granite, commonly displaying buff, pink, or light grey hues.

Obsidian

A dark volcanic glass of felsic composition formed when highly viscous, silica-rich lava is quenched almost instantaneously.

Basalt

A dark green to black, fine-grained (aphanitic) mafic extrusive igneous rock composed primarily of pyroxene and calcium-rich plagioclase feldspar, comprising the upper oceanic crust.

Gabbro

A coarse-grained (phaneritic) mafic intrusive igneous rock that is the plutonic equivalent of basalt, forming the deep underlying component of oceanic crust.

Dyke

A tabular, discordant intrusive igneous body that cuts perpendicularly or obliquely across bedding surfaces and structural layering of the host rock.

Sill

A tabular, concordant intrusive igneous pluton injected parallel to existing sedimentary bedding planes or volcanic layering.

Batholith

A massive, discordant plutonic body with an areal surface exposure exceeding $100\text{ km}^2$, often forming the core of major mountain belts.

Viscosity

The internal resistance of a fluid to flow, directly controlled in magma by temperature, volatile content, and silica concentration.

Pahoehoe Flow

A fluid basaltic lava flow that forms a smooth, billowy, or ropy surface crust as the underlying molten stream continues to advance.

Aa Flow

A basaltic lava flow characterized by a rough, jagged surface of broken, spiny blocks with gas vesicles, moving with high friction.

Pillow Lava

Tubular, elongated, bulbous lava masses formed when fluid basaltic lava is extruded subaqueously into water, causing its exterior skin to rapidly quench and rupture repeatedly.

Lava Tube

A cave-like, insulated tunnel formed beneath a hardened lava crust that allows molten lava to flow long distances away from the eruptive vent without significant cooling.

Nuée Ardente

A highly destructive, incandescent pyroclastic flow consisting of hot gases, ash, and pumice fragments that travels downslope at speeds exceeding $100\text{ km/h}$.

Lahar

A destructive mudflow or debris flow occurring on volcanic slopes, triggered when volcanic ash and debris become saturated by torrential rains or melted glacial ice and snow.

Shield Volcano

A broad, gently sloping, slightly domed volcanic structure built from successive accumulations of low-viscosity, fluid basaltic lava flows with minimal pyroclastic material.

Cinder Cone

A small, steep-sided, symmetrical volcano built from loose pyroclastic ejecta (mostly vesicular scoria lapilli) accumulated at its angle of repose, typically produced by a single short-lived eruptive phase.

Composite Volcano (Stratovolcano)

A large, nearly symmetrical, steep-sided volcano constructed of alternating layers of andesitic-to-felsic lava flows and explosive pyroclastic deposits.

Caldera

A large circular or subcircular collapse depression at a volcano's summit or across a volcanic field with a diameter exceeding $1\text{ km}$, formed by subterranean drainage or evacuation of an underlying magma chamber.

Weathering

The physical disintegration and chemical decomposition of rocks and minerals at or near Earth's surface as they adjust to ambient atmospheric conditions.

Mechanical Weathering

The physical disintegration of rock into smaller fragments without altering its underlying chemical or mineralogical composition.

Chemical Weathering

The chemical breakdown and decomposition of rock-forming minerals into one or more new compounds through contact with water, atmospheric gases, and organic substances.

Differential Weathering

The variation in the rate and degree of weathering exhibited across rock bodies caused by differences in rock composition, mineral hardness, fracturing, and local exposure.