Andalusia PAU Geology and Environmental Sciences flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Divergent plate boundary

A boundary where two plates move apart, creating new oceanic lithosphere at mid-ocean ridges with normal faulting, shallow earthquakes and tholeiitic basaltic volcanism.

Subduction zone magmatism

Water released from the descending slab lowers the mantle peridotite solidus, generating calc-alkaline andesitic to granitic magmas that build volcanic arcs above the Wadati-Benioff zone.

Bowen's reaction series

The sequence in which silicate minerals crystallise from cooling magma, from olivine and Ca-plagioclase at high temperature to quartz, K-feldspar and muscovite at low temperature.

Blueschist facies

A metamorphic facies formed at high pressure and low temperature, typical of subduction zones, characterised by glaucophane, lawsonite and jadeite in mafic protoliths.

Brittle-ductile transition

The depth range in the crust where deformation changes from fracturing and faulting to ductile flow, typically around 10-15 km depending on temperature and rock type.

Anticline versus syncline

An anticline is an upward-arching fold with the oldest strata in its core; a syncline is a downward-arching fold with the youngest strata in its core.

Mohs hardness scale

A relative scale from 1 (talc) to 10 (diamond) ranking minerals by resistance to scratching; fingernail is about 2.5, copper coin 3.5, steel knife 5.5, glass 5.5-6.

Silicate tetrahedron

The SiO4 structural unit in which one silicon atom is surrounded by four oxygen atoms; its polymerisation as isolated, chain, sheet or framework structures defines the main mineral groups.

Phaneritic versus aphanitic texture

Phaneritic igneous rocks have visible crystals formed by slow cooling at depth; aphanitic rocks have crystals too small to see, formed by rapid cooling at or near the surface.

Clastic sedimentary rock classification

Clastic rocks are classified by grain size: conglomerate and breccia (coarse), sandstone (medium), siltstone and shale (fine); rounding, sorting and cement record transport and diagenesis.

Foliated metamorphic rocks

Rocks with a planar fabric formed under directed pressure: slate, phyllite, schist and gneiss in order of increasing metamorphic grade and crystal size.

Principle of superposition

In an undisturbed sequence of sedimentary rocks, each layer is older than the one above it and younger than the one below it, giving relative ages.

Index fossil criteria

A fossil useful for correlation must have a short stratigraphic range, wide geographic distribution, be abundant and identifiable, and be independent of facies.

End-Permian mass extinction

The largest known extinction, about 252 million years ago, eliminating roughly 90% of marine species, linked to Siberian Traps volcanism, warming and ocean anoxia.

Unconformity types

Angular unconformity: tilted strata overlain by flat-lying beds; disconformity: erosion surface between parallel beds; nonconformity: sedimentary rocks over igneous or metamorphic basement.

Radiocarbon dating limit

Carbon-14 dating applies to organic remains younger than about 50,000 years because of its 5,730-year half-life; older material requires uranium-series, potassium-argon or other methods.

Porphyry copper deposit

A large low-grade copper-molybdenum-gold deposit formed by hydrothermal fluids around a felsic porphyritic intrusion, typically associated with subduction-related magmatic arcs.

Aquifer porosity versus permeability

Porosity is the fraction of rock volume that can store water; permeability is the ability to transmit it. High porosity without connected pores gives poor permeability.

Landslide classification

Mass movements are classified by material (rock, debris, earth) and mechanism: falls, topples, slides (rotational or translational), flows and creep, with velocity as an additional descriptor.

Return period

The average interval between events of a given magnitude; the annual exceedance probability equals one divided by the return period, so a 100-year flood has 1% annual chance.

Strike and dip notation

Strike is the compass direction of a horizontal line on a bedding plane; dip is the angle of steepest descent perpendicular to strike, recorded with its direction.

Troposphere

The lowest atmospheric layer, where temperature decreases with height at about 6.5 °C per kilometre and where most weather, clouds and water vapour occur.

Thermohaline circulation

Deep ocean circulation driven by density differences from temperature and salinity, with cold salty water sinking in the North Atlantic and driving a global conveyor belt.

Soil profile horizons

Vertical sequence O (organic litter), A (humus and topsoil), B (subsoil accumulation), C (weathered parent material) and R (bedrock), shaped by climate, organisms, relief and time.

Albedo

The fraction of incoming solar radiation reflected by a surface; snow and ice have high albedo, oceans and forests low albedo, affecting the planetary energy budget.

Photochemical smog

A brownish haze formed when nitrogen oxides and volatile organic compounds react in sunlight, producing tropospheric ozone, aldehydes and peroxyacetyl nitrate.

Eutrophication

Nutrient enrichment of water by nitrogen and phosphorus, causing algal blooms, oxygen depletion, fish kills and loss of biodiversity in lakes, rivers and coastal seas.

BOD5

Biochemical oxygen demand measured over five days: the oxygen consumed by microorganisms decomposing organic matter in a water sample, indicating organic pollution load.

Acid deposition

Sulphur dioxide and nitrogen oxides oxidise to sulphuric and nitric acids, lowering rain pH below 5.6 and causing soil acidification, aluminium mobilisation and freshwater damage.

Environmental Impact Assessment

A procedure that predicts environmental effects of a proposed project before approval, through screening, scoping, baseline study, impact prediction, mitigation, public consultation and monitoring.

Risk equation

Risk is the product of hazard, exposure and vulnerability: hazard is the probability of a damaging event, exposure the people or assets present, vulnerability their susceptibility to damage.

Natura 2000 network

A European network of protected areas comprising Special Protection Areas under the Birds Directive and Special Areas of Conservation under the Habitats Directive.