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PAU Geología y Ciencias Ambientales (Cantabria) study materials
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PAU Geología y Ciencias Ambientales (Cantabria) practice questions

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Question 1Geology, Earth systems, resources, hazards and environmental evidence

What behavior characterizes P (primary or longitudinal) seismic waves as they travel through Earth’s interior?

  1. They propagate through both solids and liquids, compressing and dilating material in the travel direction. Correct answer.
  2. They travel only through solids and their speed drops to zero on entering the outer core.
  3. They are shear waves vibrating perpendicular to travel direction and are the slowest waves.
  4. They are exclusively surface waves causing the greatest structural damage in earthquakes.

Explanation

P waves are compressional (longitudinal) waves that can travel through solids and liquids via periodic volume/density changes, arriving first at seismographs.

Question 2Geology, Earth systems, resources, hazards and environmental evidence

In the dynamic model of Earth’s interior, how is the lithosphere defined relative to the asthenosphere?

  1. The lithosphere is a purely metallic Fe–Ni layer, while the asthenosphere is anhydrous silicates.
  2. The lithosphere comprises crust plus part of the upper mantle with rigid, brittle behavior, floating on a ductile, deformable asthenosphere. Correct answer.
  3. The lithosphere is only emergent continental crust, while the asthenosphere is all subducted oceanic lithosphere.
  4. The lithosphere lies from 2900 km depth to Earth’s center, separated by the Gutenberg discontinuity.

Explanation

Dynamically, the lithosphere is the rigid outer shell of crust plus lithospheric upper mantle, resting on the weaker, ductile asthenosphere that enables plate motion.

Question 3Geology, Earth systems, resources, hazards and environmental evidence

Which seismic fact unequivocally shows that Earth’s outer core is liquid?

  1. Sudden P-wave acceleration at 35 km depth at the Moho.
  2. Total reflection of Rayleigh waves at submarine continental margins.
  3. An S-wave shadow zone between about 103° and 142° from the epicenter because S waves cannot travel through liquids. Correct answer.
  4. Doubling of P-wave amplitude in the lower mantle due to molten-iron viscosity.

Explanation

S waves are shear waves needing rigidity; they stop at the mantle–core boundary (~2900 km), producing a wide S-wave shadow that proves the outer core is liquid.

Question 4Geology, Earth systems, resources, hazards and environmental evidence

What characterized the Variscan (Hercynian) Orogeny in Iberia’s geological evolution?

  1. Recent opening of the Cantabrian Sea in the late Neogene by Iberia separating from Europe.
  2. Build-up of Quaternary deltas in the Bay of Biscay after Pleistocene glacial retreat.
  3. Formation of extensional grabens creating the Duero and Ebro foreland basins.
  4. Late Paleozoic (Carboniferous–Permian) continental collision that consolidated the Iberian Massif as part of Pangaea. Correct answer.

Explanation

The Variscan/Hercynian orogeny at the end of the Paleozoic built the igneous–metamorphic basement of the Iberian Massif (including the Cantabrian Zone) within Pangaea.

Question 5Geology, Earth systems, resources, hazards and environmental evidence

At a convergent subduction boundary, what is the Benioff (Wadati–Benioff) plane?

  1. The inclined plane along which earthquake foci concentrate from friction of the descending slab. Correct answer.
  2. The horizontal surface separating oceanic and continental lithosphere at asymmetric ridges.
  3. A dextral transform tear linking an accretionary prism to an intraplate hotspot.
  4. The zone of pillow-lava accumulation on a mid-ocean ridge crest.

Explanation

The Wadati–Benioff zone is the inclined seismic belt marking the subducting oceanic plate’s path into the mantle, with foci deepening landward.

Question 6Geology, Earth systems, resources, hazards and environmental evidence

How did paleomagnetic anomaly studies of ocean floors support seafloor-spreading theory?

  1. They showed marine basalt lacks magnetic minerals such as magnetite.
  2. They revealed magnetization stripes symmetric and parallel to ridges with alternating normal and reversed polarity. Correct answer.
  3. They proved oceanic crust age is uniform worldwide (~4 Ga).
  4. They confirmed continental drift is driven solely by lunar/solar gravity.

Explanation

Vine and Matthews (1963) showed ridge basalts record geomagnetic polarity; symmetric stripes parallel to ridges record spreading over time.

Question 7Geology, Earth systems, resources, hazards and environmental evidence

What is the main genesis of intraplate hotspot volcanism such as the Canary Islands or Hawaii?

  1. Direct tectonic friction between colliding continental plates.
  2. Dehydration of clay minerals in deep trenches.
  3. Ascent of deep-mantle thermal plumes (possibly from the D″ layer) causing melting by overheating. Correct answer.
  4. Gravitational collapse of large salt domes in back-arc basins.

Explanation

Hotspots arise from mantle plumes: narrow hot columns rising from deep mantle that melt near the lithosphere, building volcanic chains as plates move.

Question 8Geology, Earth systems, resources, hazards and environmental evidence

During Mesozoic–Cenozoic time the Cantabrian Mountains underwent complex tectonics. Which geodynamic event drove thrusting of Cantabrian marine lithosphere and Alpine orogenic uplift?

  1. Separation of South America and opening of the South Atlantic.
  2. A late Cretaceous asteroid impact in the Bay of Biscay.
  3. Late Triassic extensional rifting and high-T metamorphism alone.
  4. N–S convergence between Eurasia and Iberia with counterclockwise Iberian rotation and partial closing of the Bay of Biscay. Correct answer.

Explanation

Alpine structure of the Cantabrian range formed during Iberia–Eurasia convergence after Cretaceous extensional opening of the Bay of Biscay, then compressional inversion and uplift.

Question 9Geology, Earth systems, resources, hazards and environmental evidence

In magmatic differentiation by fractional crystallization, how do silicates generally behave as magma temperature falls?

  1. High-T ferromagnesian minerals (e.g., olivine) crystallize first, leaving a progressively more felsic, silica-rich residual melt. Correct answer.
  2. Quartz and felsic micas crystallize first, concentrating Fe–Mg in a final pegmatitic phase.
  3. Magma composition stays identical throughout cooling with no change in crystal proportions.
  4. Plagioclase evolves from sodic (albite) to calcic (anorthite) as temperature falls.

Explanation

Bowen’s reaction series shows high-T ferromagnesians and calcic plagioclase crystallize early; residual melt becomes more silicic/felsic as those crystals are removed.

Question 10Geology, Earth systems, resources, hazards and environmental evidence

In which geodynamic setting does high-pressure, low-temperature metamorphism (blueschist and eclogite facies) develop?

  1. Thermal contact aureoles around shallow post-orogenic granite plutons.
  2. Subduction trenches, where cold oceanic lithosphere descends rapidly, raising pressure faster than temperature equilibrates. Correct answer.
  3. Mid-ocean ridges due to high-T seawater hydrothermal circulation.
  4. Subsiding sedimentary basins under purely burial metamorphism.

Explanation

HP/LT metamorphism is diagnostic of subduction: cold slabs are buried deep quickly, producing blueschists/eclogites before heating catches up.

Question 11Geology, Earth systems, resources, hazards and environmental evidence

What is the main cause of postglacial isostatic rebound in some northern continental regions?

  1. Radioactive decay of uranium and thorium in continental lithospheric mantle.
  2. Accelerated fluvial erosion of high-discharge catchments.
  3. Vertical rise of the lithosphere responding to load reduction after ice-sheet melting. Correct answer.
  4. Gravitational pull from bulging of Earth’s core.

Explanation

By isostatic equilibrium (Airy/Pratt), melting of thick Pleistocene ice sheets unloads continents so the lithosphere slowly rebounds upward.

Question 12Geology, Earth systems, resources, hazards and environmental evidence

What geological significance do ophiolite complexes obducted onto continental margins have?

  1. Fossilized thermal groundwater reservoirs at the base of platform volcanoes.
  2. Stratigraphic evidence of Cretaceous coral reefs fossilized by aerial volcanism.
  3. Glacial sedimentary deposits marking Pleistocene ice limits.
  4. Preserved fragments of oceanic lithosphere and upper mantle tectonically emplaced onto continents during collision. Correct answer.

Explanation

An ophiolite is a tectonized oceanic-lithosphere sequence (mantle peridotite, gabbro, sheeted dikes, pillow lavas, deep-marine sediments) thrust onto continents.

Question 13Geology, Earth systems, resources, hazards and environmental evidence

What tectonic stress and plate-boundary type characterize strike-slip (transform) faults?

  1. Horizontal shear stresses at conservative boundaries where lithosphere is neither created nor destroyed. Correct answer.
  2. Vertical tensional stresses at divergent boundaries generating new oceanic crust.
  3. Compressive push in deep subduction zones with massive continental-crust destruction.
  4. Purely isostatic stresses with no seismicity or relative block motion.

Explanation

Transform faults are conservative boundaries where plates slide past each other under shear; the San Andreas is a classic example.

Question 14Geology, Earth systems, resources, hazards and environmental evidence

Seismic tomography maps mantle wave-speed anomalies. How are deep-mantle high-velocity regions interpreted?

  1. Anomalously hot melt zones that slow seismic waves.
  2. Cold, dense subducted lithosphere (slabs) sinking into the lower mantle. Correct answer.
  3. Giant cavities filled with volcanic gases under extreme pressure.
  4. Supercritical-water reservoirs originating in the inner core.

Explanation

Seismic waves travel faster through colder, stiffer, denser rock, so high-velocity (often “blue”) anomalies are interpreted as cold subducted slabs.

Question 15Geology, Earth systems, resources, hazards and environmental evidence

How does a foreland sedimentary basin form in front of a collisional orogen?

  1. By extensional stretching above an asthenospheric thermal dome.
  2. By continuous wind erosion emptying soft rocks from the mountain core.
  3. By tectonic/isostatic flexure of the foreland lithosphere under the huge load of the adjacent mountain belt. Correct answer.
  4. By sudden collapse of giant volcanic calderas after supervolcano eruptions.

Explanation

Foreland basins (e.g., Ebro, Duero) form when orogenic thrust loads flex the adjacent lithosphere, creating a subsiding trough that fills with synorogenic sediment.

Question 16Geology, Earth systems, resources, hazards and environmental evidence

Which physical factor mainly controls the transition from brittle behavior (faults/seismicity) to ductile behavior (folding) in Earth’s crust?

  1. Phosphorus concentration in the rock matrix.
  2. Percentage of air trapped in microscopic pores.
  3. Orientation of Earth’s magnetic field in austral winter.
  4. Increasing temperature, lithostatic pressure, and fluids with depth, plus strain rate. Correct answer.

Explanation

Near-surface rocks fail brittlely; with depth, higher T–P and pore fluids favor ductile flow, modulated by deformation rate.

Question 17Geology, Earth systems, resources, hazards and environmental evidence

What fundamental petrogenetic process creates large anatectic granite batholiths at the roots of continental collision orogens?

  1. Anatexis/partial melting of lower continental crust from crustal thickening and radiogenic heating. Correct answer.
  2. Direct chemical precipitation of silica at abyssal hydrothermal vents during subduction.
  3. Ultra-rapid cooling of Mg-rich komatiite lavas on emergent continents.
  4. Condensation of magmatic gases exhaled directly from the liquid metallic core.

Explanation

In collision orogens (e.g., Variscan Iberian Massif), thickened crust retains radiogenic heat, exceeding metamorphic solidus and generating crustal granite melts.

Question 18Geology, Earth systems, resources, hazards and environmental evidence

In the Wilson Cycle, what geotectonic stage was the Cantabrian margin in during the Early Cretaceous before Alpine uplift?

  1. Complete continental orogenic suture with no remaining marine space.
  2. Rift and Atlantic passive-margin development with subsiding extensional basins and Urgonian marine sedimentation. Correct answer.
  3. Mature volcanic island arc from southward subduction of the African plate.
  4. Continental intraplate hotspot over an ultrapotassic anatectic dome.

Explanation

In the Early Cretaceous, Iberia separated from France as the Bay of Biscay opened; the Cantabrian realm acted as an extensional passive margin with Urgonian facies.

Question 19Geology, Earth systems, resources, hazards and environmental evidence

In the Cantabrian Zone of the Hesperian Massif, which brittle–ductile structure dominates thin-skinned tectonic style?

  1. Extensional grabens bounded by high-angle normal faults without folding.
  2. Circular evaporite diapirs with no preferred orogenic direction.
  3. Imbricate thrust nappes and fault-propagation folds detached on Lower Paleozoic or Keuper plastic horizons. Correct answer.
  4. Vertical transcurrent transforms cutting lithospheric mantle to the asthenosphere.

Explanation

The Cantabrian Zone is renowned for Variscan thin-skinned tectonics: sedimentary cover detached on plastic levels forming stacked thrusts and folds.

Question 20Geology, Earth systems, resources, hazards and environmental evidence

What thermodynamic cause triggers partial melting of mantle peridotite in subduction zones?

  1. Pure adiabatic decompression with no temperature change or fluids.
  2. Massive lithostatic-pressure increase without chemical interaction.
  3. Overheating by mechanical friction among quartz crystals in upper continental crust.
  4. Addition of water and volatiles from dehydrating subducted oceanic plate, lowering peridotite solidus. Correct answer.

Explanation

As the slab descends, hydrated minerals dehydrate; released water fluxes the mantle wedge, lowering the peridotite solidus and generating arc magmas.

Question 21Geology, Earth systems, resources, hazards and environmental evidence

What fundamental chemical reaction drives karst dissolution weathering of limestone (CaCO3)?

  1. Conversion of insoluble calcite into soluble calcium bicarbonate Ca(HCO3)2 by CO2-charged water. Correct answer.
  2. Oxidation of Fe2+ in calcite to powdery hematite.
  3. Hydration of anhydrite to fibrous gypsum expanding mineral volume.
  4. Bacterial sulfate reduction precipitating pure fluorite in limestone pores.

Explanation

Rainwater absorbs atmospheric/soil CO2 forming carbonic acid, which converts CaCO3 into soluble Ca(HCO3)2 and dissolves limestone into karst landforms.

Question 22Geology, Earth systems, resources, hazards and environmental evidence

What is physical weathering by gelifraction (frost wedging), very active on Picos de Europa summits?

  1. Feldspar dissolution by acidic night fogs.
  2. Rock breakage by pressure of water freezing in cracks and pores. Correct answer.
  3. Concentric exfoliation from direct summer solar radiation.
  4. Cliff abrasion by continuous sand-laden wind.

Explanation

Gelifraction occurs when water in joints freezes; ice expands ~9% and wedges rock apart, producing mountain scree.

Question 23Geology, Earth systems, resources, hazards and environmental evidence

What happens to a river’s erosional and transport capacity when it reaches its absolute base level of erosion?

  1. Potential energy jumps, carving very deep canyons.
  2. Vertical erosion peaks, opening giant waterfalls.
  3. Kinetic energy for vertical erosion collapses; sedimentation and lateral reworking dominate. Correct answer.
  4. Discharge instantly evaporates from rising air temperature.

Explanation

Absolute base level is sea level. As slope approaches zero near it, kinetic energy for downcutting collapses and deposition dominates.

Question 24Geology, Earth systems, resources, hazards and environmental evidence

Which marine erosional coastal landform forms when waves undercut a cliff base until the overhang collapses?

  1. A lagoon sheltered by an eolian dune barrier.
  2. A digitate delta with sinuous distributaries.
  3. An abyssal plain covered by foraminiferal muds.
  4. A wave-cut abrasion platform at the foot of the retreating cliff. Correct answer.

Explanation

Continued wave attack notches cliff bases; collapse makes the cliff retreat, leaving a rocky platform flooded at high tide-the abrasion platform.

Question 25Geology, Earth systems, resources, hazards and environmental evidence

Which exokarst landform is a closed funnel- or caldera-shaped depression formed by limestone dissolution or collapse?

  1. A doline (sinkhole). Correct answer.
  2. A lapies/karren field.
  3. A stalagmite.
  4. A glacial cirque.

Explanation

Dolines are circular/elliptical closed depressions formed by surface dissolution along converging cracks or by cave-roof collapse.

Question 26Geology, Earth systems, resources, hazards and environmental evidence

Which gravitational process is the very slow, discontinuous, almost imperceptible downslope movement of the uppermost soil?

  1. Free vertical rockfall.
  2. Soil creep / solifluction. Correct answer.
  3. A highly viscous volcanic lahar.
  4. A high-speed powder-snow avalanche.

Explanation

Creep is slow continuous downslope soil motion from expansion/contraction cycles (freeze–thaw or wet–dry), shown by tilted trees/posts.

Question 27Geology, Earth systems, resources, hazards and environmental evidence

What is the geological origin of Cantabrian rias/estuaries such as Santander or Tina Mayor?

  1. Recent Holocene volcanic extensional grabens.
  2. Submarine craters excavated by Mesozoic tsunami impacts.
  3. Paleozoic/fluvial valleys invaded by the sea during Holocene marine transgression after the last glaciation. Correct answer.
  4. Meteorite collapse craters submerged by the Gulf Stream.

Explanation

Cantabrian rias are river valleys cut at glacial lowstands and drowned by ~120 m postglacial eustatic rise.

Question 28Geology, Earth systems, resources, hazards and environmental evidence

How do stalactites and stalagmites (speleothems) grow inside a cave?

  1. By accumulation of petrified bat guano over millennia.
  2. By atmospheric moisture swelling ceiling claystones.
  3. By condensation of magmatic sulfur vapor in cold cracks.
  4. By CO2 degassing from dripwater entering the cave air, lowering solubility and precipitating CaCO3. Correct answer.

Explanation

Bicarbonate-rich water enters cave air with lower pCO2, degasses CO2, and precipitates CaCO3 drop by drop as stalactites/stalagmites.

Question 29Geology, Earth systems, resources, hazards and environmental evidence

In mountain rivers such as the Pas or Besaya, which sediment fraction moves by saltation and rolling?

  1. Bedload-gravels, cobbles, and coarse sands moving in contact with the bed. Correct answer.
  2. Suspended load-microscopic clays held by turbulence.
  3. Dissolved load-Na+, Cl−, Ca2+ ions.
  4. Floating phytodetritus on the surface.

Explanation

Bedload is coarser denser clasts that cannot stay suspended, so they roll, slide, and saltate along the bed.

Question 30Geology, Earth systems, resources, hazards and environmental evidence

Which glacial sedimentary landform is a heterogeneous, unstratified accumulation of blocks, gravels, and fines (till) molded along/in front of the ice tongue?

  1. A drumlin of cross-bedded fluvioglacial sandstones.
  2. A moraine (lateral, medial, or terminal). Correct answer.
  3. A kame of lacustrine varved silts.
  4. An esker of well-sorted cobbles.

Explanation

Moraines are ice-dumped ridges of unsorted till at ice margins (lateral) or termini (terminal), without fluvial sorting.

Question 31Geology, Earth systems, resources, hazards and environmental evidence

Santander Bay features El Puntal spit (Somo). What coastal process builds and maintains this sandy spit?

  1. Collapse of old underground mine galleries under the coast.
  2. Exclusive eolian dune supply from the Sahara.
  3. Longshore drift driven by oblique NW waves moving sand parallel to the shoreline. Correct answer.
  4. Coarse sediment discharge by gravity avalanches from abyssal canyons.

Explanation

Longshore drift from obliquely incident waves transports sand alongshore; at bay mouths energy drops and sand progrades as a spit like El Puntal.

Question 32Geology, Earth systems, resources, hazards and environmental evidence

In a well-developed soil under Cantabria’s humid oceanic climate, what characterizes Horizon B (illuviation zone)?

  1. The topmost litter/organic layer (humus).
  2. The light leached horizon where soluble minerals were stripped.
  3. Unaltered parent rock without weathering/biology.
  4. The subsurface layer where clays, Fe/Al oxides, and carbonates washed from Horizon A accumulate. Correct answer.

Explanation

Horizon B is the accumulation/illuviation zone receiving colloids, clays, and Fe–Al hydroxides from A/E above, often reddish-brown with stronger structure.

Question 33Geology, Earth systems, resources, hazards and environmental evidence

Which runoff erosion sequence on bare slopes leads to the most severe land degradation?

  1. Raindrop splash → unconcentrated sheet flow → rill erosion → deep gully formation. Correct answer.
  2. Gully formation → eolian deflation → gelifraction → mass washing.
  3. Slow solifluction → mantle subsidence → barchan dunes → leaching.
  4. Polje formation → endokarst dissolution → wave-cut platform collapse → salt corrosion.

Explanation

Hillslope water erosion starts with splash disaggregation, then sheetwash, concentrates into rills, and deepens into irreversible gullies.

Question 34Geology, Earth systems, resources, hazards and environmental evidence

How do lichens and plant roots contribute to biological rock weathering?

  1. They raise rock solar reflectance to absolute zero.
  2. They combine mechanical wedging (root pressure in joints) with chemical attack (organic acids that chelate metals). Correct answer.
  3. They synthesize primary quartz sealing all fractures against water.
  4. They absorb rock silicates and instantly convert them to nitrogen gas.

Explanation

Biological weathering is dual: roots physically wedge joints while roots/lichens secrete organic acids that chemically alter silicates and carbonates.

Question 35Geology, Earth systems, resources, hazards and environmental evidence

In an alluvial fan/debris cone at a mountain torrent mouth, how does sediment size change from apex to toe?

  1. Fines at the apex and giant blocks at the outer toe.
  2. Absolutely uniform grain size across the fan.
  3. Coarsest blocks/cobbles at the apex where slope drops abruptly; silts/sands extend toward the toe. Correct answer.
  4. Only common salt at the apex and coal at the toe.

Explanation

Leaving the mountain confinement, slope and competence drop; heavy coarse clasts dump at the apex while fines travel farther down-fan.

Question 36Geology, Earth systems, resources, hazards and environmental evidence

Why are karst aquifers (e.g., Cantabrian limestone massifs) extremely contamination-prone versus detrital aquifers?

  1. Limestone turns pollutants into highly radioactive heavy metals.
  2. They hold no water and dry out under any chemical spill.
  3. Water moves at ~1 mm/year.
  4. High conduit permeability lets water race through large underground channels with little matrix filtration or self-purification. Correct answer.

Explanation

Karst has conduit permeability: water travels rapidly through shafts and galleries without the filtration/adsorption of sandy detrital aquifers, spreading contaminants fast.

Question 37Geology, Earth systems, resources, hazards and environmental evidence

What geotechnical soil failure occurs when unconsolidated water-saturated fine sands receive a strong seismic shock?

  1. Liquefaction-pore-water pressure cancels effective stress and the soil behaves as a fluid. Correct answer.
  2. Instant cementation of sands into quartzitic sandstone.
  3. Accelerated gelivation freezing the mass in under a second.
  4. Sublimation of silicates into gaseous plasma.

Explanation

Shaking raises pore pressure in saturated loose sands until grains lose contact strength and the mass flows like a viscous fluid.

Question 38Geology, Earth systems, resources, hazards and environmental evidence

In morphometric comparison of Cantabrian vs Mediterranean catchments, which setting favors flash floods with extremely sharp hydrograph peaks?

  1. Elongate basins with low mean slope and dense forest.
  2. Rounded basins with high drainage density, steep slopes, and poor infiltration. Correct answer.
  3. Hyper-developed karst aquifers absorbing 100% of storm rain.
  4. Wide estuaries without longshore barriers.

Explanation

Rounded basins deliver runoff to the trunk simultaneously; steep impermeable slopes shorten concentration time and spike flood peaks.

Question 39Geology, Earth systems, resources, hazards and environmental evidence

What is the geological genesis of stepped coastal rasas along the Cantabrian shore at different heights above modern sea level?

  1. Eolian accumulation terraces of intense arid droughts.
  2. Normal-fault planes from Bay of Biscay tectonic sinking.
  3. Former wave-cut abrasion platforms later uplifted by Quaternary tectonic/eustatic change. Correct answer.
  4. Ancient glacial beds carved by Miocene submarine ice tongues.

Explanation

Cantabrian rasas are fossil marine abrasion platforms cut near past sea levels, then left as steps by uplift and eustatic oscillations.

Question 40Geology, Earth systems, resources, hazards and environmental evidence

How does the Chemical Index of Alteration (CIA) help reconstruct continental paleoclimates from sedimentary horizons?

  1. It quantifies amphibole proportion in HP metamorphic rocks.
  2. It calculates polar ice volume via helium isotopes.
  3. It determines neutral pH of mountain rivers at snowmelt.
  4. High CIA reflects intense leaching of mobile cations (Na+, K+, Ca2+) leaving Al2O3-rich residue-a warm hyper-humid paleoclimate signal. Correct answer.

Explanation

CIA tracks feldspar weathering to clays; warm wet climates leach bases and raise CIA toward 100, indicating tropical/hyper-humid alteration.

Question 41Geology, Earth systems, resources, hazards and environmental evidence

In Mohs hardness scale, which sequence is correct from softest to hardest among these examples?

  1. Talco (1) < Calcite (3) < Quartz (7) < Diamond (10). Correct answer.
  2. Diamond (10) < Quartz (7) < Calcite (3) < Talco (1).
  3. Gypsum (2) < Diamond (10) < Orthoclase (6) < Fluorite (4).
  4. Corundum (9) < Apatite (5) < Talco (1) < Quartz (7).

Explanation

Mohs is an ordinal 1–10 scratch-resistance scale: talc 1 … quartz 7 … diamond 10.

Question 42Geology, Earth systems, resources, hazards and environmental evidence

Which silicate subgroup has a 3D framework where every oxygen of [SiO4] tetrahedra is shared (e.g., quartz and feldspars)?

  1. Nesosilicates with isolated tetrahedra linked by metal cations.
  2. Tectosilicates. Correct answer.
  3. Single-chain inosilicates such as pyroxenes.
  4. Phyllosilicates in infinite parallel sheets.

Explanation

Tectosilicates share 100% of tetrahedral oxygens in a 3D framework; quartz and feldspars belong here.

Question 43Geology, Earth systems, resources, hazards and environmental evidence

Which sequence shows progressive regional metamorphic grade starting from an original shale/clay?

  1. Slate → Schist → Gneiss → Migmatite. Correct answer.
  2. Marble → Quartzite → Basalt → Granite.
  3. Marl → Gypsum → Halite → Sylvite.
  4. Chert → Coal → Serpentine → Eclogite.

Explanation

With rising P–T, shale evolves slate → phyllite → schist → gneiss and finally migmatite at the onset of partial melting.

Question 44Geology, Earth systems, resources, hazards and environmental evidence

What characterized Early Cretaceous Urgonian facies limestones widely developed in Cantabria?

  1. Abyssal marine muds at >5000 m in subduction trenches.
  2. Eolian loess of cold continental desert climate.
  3. Shallow warm well-lit carbonate platforms built of rudists, corals, and foraminifers. Correct answer.
  4. Glacial tills intercalated with submarine pillow basalts.

Explanation

Urgonian facies are shallow warm tropical carbonate platforms rich in rudists, corals, and orbitolinid foraminifers.

Question 45Geology, Earth systems, resources, hazards and environmental evidence

In Bowen’s Reaction Series, which minerals crystallize first on the discontinuous and continuous branches as basaltic magma cools?

  1. Discontinuous: quartz; continuous: muscovite.
  2. Discontinuous: biotite; continuous: albite.
  3. Discontinuous: orthoclase; continuous: nepheline.
  4. Discontinuous: olivine; continuous: calcic plagioclase (anorthite). Correct answer.

Explanation

At the highest temperatures (~1200 °C), discontinuous-branch olivine and continuous-branch calcic plagioclase (anorthite) appear first.

Question 46Geology, Earth systems, resources, hazards and environmental evidence

Historic Reocin Mine (Cantabria) was a major European zinc producer. What is the principal zinc ore mineral of this hydrothermal–sedimentary replacement deposit?

  1. Sphalerite/blende (ZnS) with galena (PbS) replacing Urgonian dolomite. Correct answer.
  2. Cinnabar (HgS) in high-pressure quartz veins.
  3. Chalcopyrite (CuFeS2) in deep subduction gabbros.
  4. Bauxite (Al2O3·nH2O) in Triassic lacustrine basins.

Explanation

Reocin is an epigenetic MVT-style replacement in Urgonian dolomites; the main Zn ore is caramel sphalerite (ZnS) with galena.

Question 47Geology, Earth systems, resources, hazards and environmental evidence

In what Paleozoic sedimentary setting did the major Carboniferous coal seams of the Astur–Cantabrian basin form?

  1. Hyper-saline arid dune savannas.
  2. Subsiding equatorial coastal forests with abundant tree ferns and lycophytes (limnic/paralic swamp settings). Correct answer.
  3. Deep bathyal coral reefs with methane venting.
  4. Abyssal volcanic floors during pillow-basalt eruption.

Explanation

Carboniferous coal accumulated in equatorial deltaic/coastal swamps (paralic) where lycophyte forests formed anoxic peats later buried to bituminous coal.

Question 48Geology, Earth systems, resources, hazards and environmental evidence

Which index metamorphic mineral indicates very high-grade conditions (high T and P) in pelitic rocks among Al2SiO5 polymorphs?

  1. Chlorite.
  2. Kaolinite.
  3. Sillimanite. Correct answer.
  4. Talc.

Explanation

Among andalusite, kyanite and sillimanite, sillimanite marks the highest T–P conditions of the Al2SiO5 triad in high-grade pelites.

Question 49Geology, Earth systems, resources, hazards and environmental evidence

What biological and taphonomic requirements make an excellent biostratigraphic index (guide) fossil?

  1. Very long temporal range and a tiny geographic distribution.
  2. Soft unmineralized soft-parts and exclusive lacustrine freshwater habitat.
  3. Zero mutation rate and exclusive subterranean karst-cave occurrence.
  4. Rapid phylogenetic evolution (short stratigraphic range), wide geographic distribution, and abundant fossilization. Correct answer.

Explanation

Guide fossils (e.g., ammonites, graptolites) need short chronologic ranges for fine resolution plus wide abundance and distribution for correlation.

Question 50Geology, Earth systems, resources, hazards and environmental evidence

Cantabrian coastal Flysch (e.g., San Vicente de la Barquera) consists of turbidite sequences. Which internal sedimentary structure of a Bouma sequence is typical?

  1. Upward-fining graded bedding from gradual deceleration of the turbidity current. Correct answer.
  2. Upward-coarsening grading with the largest blocks at the top.
  3. Eolian cross-lamination by submarine dunes without clay.
  4. Concentric anhydrite evaporite layers intercalated with lignite seams.

Explanation

Turbidity currents deposit coarsest grains first as they decelerate on the abyssal plain, producing classic fining-upward Bouma divisions.