Earth and Environmental Science: Geosphere, Tectonics, and Rock Cycles

Comprehensive vocabulary flashcards covering the geosphere, global cycling systems, plate tectonics, rock classification, the rock cycle, and earthquake mechanics.

Geosphere

The Earth system encompassing Earth's core, molten and solid rock, soil, dirt, and sediments.

Hydrosphere

The Earth system encompassing water in all its forms.

Atmosphere

The mixture of gases surrounding the planet.

Biosphere

The Earth system comprising all life and living things.

Carbon Cycle

The biogeochemical cycle where matter is transferred and transformed through Earth's systems via four main processes: photosynthesis, consumption/assimilation, respiration and decomposition, and combustion.

Nitrogen Cycle

The matter cycling system consisting of four primary processes: ammonification, nitrogen fixation, nitrification, and denitrification.

Nitrogen Fixation

The process in the nitrogen cycle where soil bacteria convert atmospheric nitrogen ($N_2$) into forms usable by plants.

Ammonification

The decomposition process in the nitrogen cycle where decomposers break down dead matter and waste from animals into ammonia compounds.

Nitrification

The conversion process in the soil where bacteria turn ammonia into nitrites and nitrates that can be absorbed by plant roots.

Denitrification

The process in the nitrogen cycle that returns nitrogen from the soil back into the atmosphere.

Continental Drift

The theory proposed by Alfred Wegener stating that all continents were once joined into a single landmass called 'Pangea' and have drifted apart over geological time.

Pangea

The single ancient supercontinent that Alfred Wegener proposed formerly comprised all modern continents before they drifted apart.

Lithosphere

The rigid outer layer of Earth composed of the crust and the rigid upper mantle (lithospheric mantle), broken into tectonic plates that move from $0$ to about $15\,\text{cm}$ per year.

Asthenosphere

The semi-solid layer of the mantle directly beneath the lithospheric mantle upon which tectonic plates rest and move.

Oceanic Crust

A dense type of crust that is usually $5\text{--}10\,\text{km}$ thick and primarily composed of basalt.

Continental Crust

A relatively light crustal layer that is usually between $20\text{--}70\,\text{km}$ thick.

Plate Boundary

The border where two tectonic plates meet, categorised into types where plates push together, pull apart, or slide past each other.

Convection Currents

A mechanism of plate motion where a tectonic plate is dragged along by circulating mantle material, driven by hotter mantle rising and cooler mantle sinking.

Ridge Push

A driver of plate tectonics where a plate is pushed outward by the weight and elevation of an elevated mid-ocean ridge.

Slab Pull

A driver of plate tectonics where a plate is pulled downward into the mantle by the weight of its cold, dense subducting section.

Divergent Boundary

A plate boundary where two neighbouring tectonic plates move apart from one another, creating new crust.

Rift Valley

A long depression created by a divergent plate boundary within continental crust, accompanied by rising magma and volcanoes, such as the East African rift valley.

Mid-Ocean Ridge

An underwater mountain range formed at an oceanic-oceanic divergent boundary where magma rises to create new oceanic crust and drive seafloor spreading, such as the Mid-Atlantic Ridge.

Convergent Boundary

A plate boundary where two neighbouring tectonic plates collide or move toward each other, resulting in crust destruction or mountain formation.

Subduction

The process at a convergent boundary where a denser tectonic plate sinks beneath a less dense plate into the mantle.

Ocean Trench

A deep seafloor valley formed at a convergent boundary when one oceanic plate subducts beneath another into the mantle.

Transform Boundary

A boundary where two tectonic plates slide past each other horizontally without creating or destroying crust.

Minerals

Naturally occurring, inorganic solid substances that serve as the fundamental building blocks of rocks.

Rocks

Naturally formed solid masses composed of one or more minerals produced by internal or surface geological processes rather than biological actions.

Igneous Rock

A type of rock formed by the cooling and solidification of molten rock (magma or lava).

Magma

Molten rock located beneath Earth's surface.

Lava

Molten rock that has erupted onto Earth's surface.

Plutonic (Intrusive) Igneous Rock

Igneous rock formed from magma that cooled slowly beneath Earth's surface, developing large crystal sizes (e.g., granite, gabbro).

Volcanic (Extrusive) Igneous Rock

Igneous rock formed from lava that cooled quickly above Earth's surface, resulting in small crystals or no crystals (e.g., obsidian, pumice, basalt).

Mechanical Weathering

The physical breakdown of rock into smaller particles without altering its mineral chemical composition, driven by temperature change, frost action, root action, and animal burrowing.

Chemical Weathering

The breakdown of rocks into smaller particles through reactions that alter the chemical composition of minerals, driven by oxygen, rainwater, and carbon dioxide.

Erosion

The gradual wearing away and removal of rock at Earth's surface, primarily driven by water, glaciers, and wind.

Sedimentary Rock

A type of rock formed through the accumulation, compaction, and lithification of sediment layers.

Lithification

The geological process by which loose sediments undergo compaction and cementation to form solid sedimentary rock.

Strata

Distinct, parallel layers or beds of sedimentary rock found within geological formations.

Compaction

The process where sediments are squeezed together by the weight and pressure of overlying deposited layers.

Cementation

The process where dissolved minerals crystallise as water evaporates, binding sediment grains together.

Recrystallization

A process where mineral crystals in sediment change structural configuration or grow anew between sediment grains when exposed to water.

Clastic Sedimentary Rocks

Sedimentary rocks composed of weathered fragments and minerals of pre-existing rocks that have undergone deposition, compaction, and lithification.

Biological (Organic) Sedimentary Rocks

Sedimentary rocks formed from the compacted and lithified remains of once-living organisms, such as coal from plants or limestone from shells and corals.

Chemical Sedimentary Rocks

Sedimentary rocks formed when dissolved minerals precipitate out of evaporating water, such as cave stalactites and stalagmites.

Metamorphic Rock

A type of rock formed when an existing protolith is structurally altered by intense heat and/or pressure without completely melting.

Protolith

The original precursor rock—sedimentary, igneous, or metamorphic—that undergoes metamorphism to produce a metamorphic rock.

Regional Metamorphism

Metamorphism occurring over extensive geographic areas deep within the crust under intense temperature and pressure, typically displaying foliation and increased grain size.

Foliation

The parallel alignment of flaky, platy minerals into distinct layers under differential pressure during regional metamorphism.

Contact Metamorphism

Localised thermal metamorphism that occurs when rock is baked and altered by proximity to high-temperature molten magma or an igneous intrusion.

Rock Cycle

An idealised continuous series of geological processes through which any rock type can be transformed into any other rock type over time.

Earthquake

Ground tremors caused by the sudden slip of two blocks of Earth's crust past each other along a fault.

Fault

A fracture or zone of displacement in Earth's crust along which blocks of rock move relative to one another.

Focus

The underground point along a fault where the sudden slip of rock initiates during an earthquake.

Epicentre

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

Seismograph

An instrument that detects and records earthquake vibrations along three axes: east/west, north/south, and up/down.

Moment Magnitude Scale ($M_w$)

A unitless logarithmic earthquake scale where each whole-number increment indicates a tenfold ($10\times$) increase in recorded ground motion.

P-waves (Primary Waves)

The fastest seismic waves (speed approximately $10\,\text{km/s}$); longitudinal push-pull waves that travel through both the solid and liquid interior of Earth.

S-waves (Secondary Waves)

Transverse side-to-side seismic waves travelling at approximately $5\,\text{km/s}$ that move exclusively through solid Earth materials and cannot pass through liquids.

Surface Waves

The slowest seismic waves (speed approximately $4\,\text{km/s}$); Rayleigh-type rolling waves that travel strictly along Earth's exterior surface.

Seismic Lag Time

The time difference between the arrival of the first P-wave and the first S-wave on a seismogram, used to calculate distance to the earthquake epicentre.