Extremadura PAU Geology and Environmental Sciences Exam flashcards

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

Uniformitarianism

Principle stating that the same physical, chemical and biological processes observed today operated in the geological past, so ancient rocks can be explained by present-day processes acting over long times.

S-wave shadow zone

Region on the opposite side of the Earth from an earthquake where no S waves are recorded, because shear waves cannot pass through the liquid outer core.

Isostasy

Model in which rigid lithospheric plates float in gravitational equilibrium on the denser asthenosphere; thicker, less dense continental crust stands higher than oceanic crust.

Mohs hardness scale

Relative scale from 1 (talc) to 10 (diamond) ranking minerals by which can scratch which; used to identify minerals in hand specimens alongside cleavage, lustre and streak.

Bowen's reaction series

Sequence in which minerals crystallize from cooling magma: olivine, pyroxene and amphibole first at high temperature, then biotite, feldspars, muscovite and quartz last.

Foliation

Parallel alignment of platy minerals such as mica and chlorite under directed pressure, producing the layered appearance of slate, schist and gneiss in regional metamorphism.

Clastic sedimentary rock

Rock made of fragments of pre-existing rocks classified by grain size: conglomerate (gravel), sandstone (sand) and shale (silt and clay), usually cemented by calcite or silica.

Seafloor spreading

Process at mid-ocean ridges where new basaltic crust forms from upwelling magma and moves away symmetrically, recorded by magnetic stripes and increasing sediment thickness with distance.

Wadati-Benioff zone

Inclined zone of deepening earthquake foci that traces a subducting slab from the ocean trench down hundreds of kilometres into the mantle.

Magma viscosity

Resistance to flow controlled mainly by silica content and temperature; high-silica, cooler magma is viscous and erupts explosively, whereas basaltic magma flows easily.

Metamorphic facies

Set of mineral assemblages that record a specific range of pressure and temperature, such as greenschist, amphibolite, granulite, blueschist and eclogite.

Elastic rebound

Explanation of earthquakes: strain accumulates in rocks on either side of a locked fault until strength is exceeded, the fault slips and stored energy radiates as seismic waves.

Hydrolysis weathering

Chemical reaction of minerals with water, notably converting feldspars into clay minerals and dissolved ions; dominant in warm, humid climates and a key step in soil formation.

Karst landscape

Landscape formed by dissolution of limestone, with caves, sinkholes, dolines and disappearing streams; underground drainage replaces surface rivers and water flows rapidly through conduits.

Cross-bedding

Inclined layers within a sedimentary bed formed by migrating dunes or ripples; the dip direction indicates the ancient current or wind direction.

Graded bedding

Layer in which grain size decreases upward, deposited by a waning current such as a turbidity current; the sequence records decreasing transport energy.

Coriolis effect

Apparent deflection of moving air and water caused by Earth's rotation: to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, shaping winds and currents.

Greenhouse effect

Process in which atmospheric gases absorb outgoing infrared radiation and re-emit part toward the surface, keeping mean surface temperature about 33 degrees Celsius warmer than without an atmosphere.

Albedo

Fraction of incoming solar radiation reflected by a surface; ice and snow have high albedo, oceans and forests low albedo, so ice loss creates a positive warming feedback.

El Niño–Southern Oscillation

Coupled ocean-atmosphere cycle in the tropical Pacific: weakened trade winds warm eastern Pacific waters during El Niño, altering rainfall worldwide; La Niña is the cool opposite phase.

Thermohaline circulation

Global deep-ocean circulation driven by differences in temperature and salinity, which set water density; it transports heat between latitudes over timescales of centuries.

Aquifer

Geological formation with sufficient porosity and permeability to store and transmit usable quantities of groundwater; confined aquifers lie beneath an impermeable layer.

Spring tide

Unusually high and low tides occurring at new and full moon, when the gravitational pulls of the Sun and Moon align and reinforce each other.

River regime

Pattern of seasonal variation in a river's discharge, described as nival, pluvial or mixed according to whether snowmelt, rainfall or both dominate the flow.

Soil profile horizons

Vertical sequence of soil layers: O organic litter, A humus-rich topsoil, E leached horizon, B accumulation horizon, C weathered parent material and R bedrock.

Soil salinization

Accumulation of soluble salts in the upper soil from irrigation with saline water and high evaporation in arid climates, reducing fertility and crop yields.

Ecological succession

Progressive change in community composition over time, from pioneer species on bare substrate to a more stable climax community, reset by disturbances such as fire.

Dehesa

Extensive Iberian agrosilvopastoral system of scattered holm and cork oaks with grassland, grazed by livestock and important for steppe birds and soil conservation.

Acid mine drainage

Pollution formed when sulfide minerals such as pyrite oxidize in contact with water and air, producing acidic, metal-rich runoff that damages rivers and groundwater.

Environmental impact assessment

Procedure that predicts the environmental effects of a proposed project before approval, compares alternatives and defines mitigation and monitoring measures with public participation.

Ecological footprint

Area of biologically productive land and water needed to supply a population's resources and absorb its wastes, expressed in global hectares.

Risk versus hazard

Hazard is the potentially damaging event; risk combines hazard probability with exposure and vulnerability, so the same hazard can produce very different risk.

Desertification

Land degradation in arid and semi-arid zones caused by drought and human pressure such as overgrazing, deforestation and poor irrigation, reducing soil productivity.