Eduqas A-level Geology · F2

Surface and internal processes of the rock cycle

Exam-style questions with answers for F2 Surface and internal processes of the rock cycle in Eduqas A-level Geology (spec A480QS). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below.

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Question 1 · Spec F2, Key Idea 1 · Energy sources
Compare the external and internal energy sources that drive the rock cycle. [2 marks]
Answer:
External: solar energy drives the water cycle, weathering and erosion (1); internal: primordial heat and radioactive decay drive igneous, metamorphic and tectonic processes (1).
Question 2 · Spec F2, Key Idea 1 · Physical weathering
Explain how freeze-thaw weathering breaks down jointed rock. [3 marks]
Answer:
Water enters joints and cracks (1); it freezes and expands by about 9% (1); repeated freezing and thawing widens the cracks until angular fragments break off (1).
Question 3 · Spec F2, Key Idea 1 · Physical weathering
Explain how insolation weathering breaks down rock. [2 marks]
Answer:
Repeated heating and cooling cause minerals to expand and contract at different rates (1); setting up stresses that loosen grains or flakes of rock (1).
Question 4 · Spec F2, Key Idea 1 · Chemical weathering
Describe the products of hydrolysis of feldspar. [2 marks]
Answer:
Clay minerals such as kaolinite (1); and ions in solution, such as K⁺, with some silica (1).
Question 5 · Spec F2, Key Idea 1 · Chemical weathering
Explain how carbonation dissolves limestone. [2 marks]
Answer:
Carbon dioxide dissolves in rainwater to form weak carbonic acid (1); which reacts with calcium carbonate to form soluble calcium hydrogencarbonate (1).
Question 6 · Spec F2, Key Idea 1 · Chemical weathering
Explain why iron-rich rocks develop a red-brown weathered surface. [2 marks]
Answer:
Iron in minerals is oxidised from Fe²⁺ to Fe³⁺ (1); forming red-brown iron oxides or hydroxides (1).
Question 7 · Spec F2, Key Idea 1 · Biological weathering
Describe one physical and one chemical effect of organisms on weathering. [2 marks]
Answer:
Physical: plant roots grow into cracks and widen them (1); chemical: organic acids from roots or decay dissolve or alter minerals (1).
Question 8 · Spec F2, Key Idea 1 · Erosion
Distinguish between abrasion and attrition. [2 marks]
Answer:
Abrasion is the wearing of a surface by sediment carried against it (1); attrition is the wearing of the particles themselves as they collide (1).
Question 9 · Spec F2, Key Idea 1 · Transport
Describe the four ways sediment is transported by a river. [4 marks]
Answer:
Traction: rolling along the bed (1); saltation: bouncing (1); suspension: fine particles carried in the water (1); solution: dissolved ions (1).
Question 10 · Spec F2, Key Idea 1 · Deposition
Explain why coarse sediment is deposited first as a current slows. [2 marks]
Answer:
The current loses energy and competence (1); so it can no longer carry the largest particles, while fine particles stay suspended (1).
Question 11 · Spec F2, Key Idea 1 · Deposition
Explain why clay is deposited where rivers enter the sea. [2 marks]
Answer:
Ions in seawater cause clay particles to stick together (flocculate) (1); the larger flocs settle out more quickly (1).
Question 12 · Spec F2, Key Idea 1 · Sandstone description
State four grain properties to record before interpreting a sandstone's environment. [4 marks]
Answer:
Any four from: grain size (1); roundness (1); sphericity (1); sorting (1); mineral composition (1); type of cement or matrix (1).
Question 13 · Spec F2, Key Idea 1 · Sandstones
Describe how arkose differs from a mature quartz sandstone. [2 marks]
Answer:
Arkose contains more than 25% feldspar (1); a mature quartz sandstone is almost all quartz with little unstable material (1).
Question 14 · Spec F2, Key Idea 1 · Sandstones
State three features that identify greywacke. [3 marks]
Answer:
Poor sorting with angular grains (1); rock (lithic) fragments (1); more than 15% fine-grained matrix (1).
Question 15 · Spec F2, Key Idea 1 · Rudites
Distinguish between conglomerate and breccia. [2 marks]
Answer:
Both contain clasts larger than 2 mm (1); conglomerate clasts are rounded, breccia clasts are angular (1).
Question 16 · Spec F2, Key Idea 1 · Mudrocks
Distinguish between shale and mudstone. [2 marks]
Answer:
Shale is fissile and splits into thin layers parallel to bedding (1); mudstone is massive and does not split this way (1).
Question 17 · Spec F2, Key Idea 1 · Limestones
Identify a limestone made of rounded, concentrically coated grains and state its environment. [2 marks]
Answer:
Oolitic limestone (1); formed in warm, shallow, agitated, carbonate-rich seas (1).
Question 18 · Spec F2, Key Idea 1 · Limestones
State the evidence for a biogenic origin of shelly limestone. [1 mark]
Answer:
It is mostly made of recognisable shell fragments or other skeletal remains.
Question 19 · Spec F2, Key Idea 1 · Limestones
Describe chalk and its environment of deposition. [2 marks]
Answer:
A fine-grained white limestone made of microscopic coccoliths (1); deposited in a warm, clear, deep marine environment with little land-derived sediment (1).
Question 20 · Spec F2, Key Idea 1 · Evaporites
Explain how evaporite rocks form. [2 marks]
Answer:
Evaporation of seawater or lake water concentrates dissolved ions (1); until minerals such as gypsum and halite precipitate (1).
Question 21 · Spec F2, Key Idea 1 · Sedimentary structures
Distinguish between graded bedding and cross-bedding. [2 marks]
Answer:
Graded bedding shows grain size decreasing upwards within a bed (1); cross-bedding shows inclined layers formed by migrating ripples or dunes (1).
Question 22 · Spec F2, Key Idea 1 · Sedimentary structures
State the origin of symmetrical and asymmetrical ripple marks. [2 marks]
Answer:
Symmetrical ripples form by oscillating wave action (1); asymmetrical ripples form by a current flowing in one direction (1).
Question 23 · Spec F2, Key Idea 1 · Palaeocurrents
An asymmetrical ripple has a gentle western slope and a steep eastern slope. State the current direction and explain your answer. [2 marks]
Answer:
West to east (1); sediment moves up the gentle stoss side and avalanches down the steep lee side (1).
Question 24 · Spec F2, Key Idea 1 · Sedimentary structures
State what desiccation cracks show about the environment. [1 mark]
Answer:
Wet sediment was exposed to the air and dried out, for example on a floodplain or tidal flat.
Question 25 · Spec F2, Key Idea 1 · Sedimentary structures
Explain how load casts and flame structures form. [2 marks]
Answer:
Dense sand is deposited on soft, water-rich mud and sinks into it as bulges (load casts) (1); the mud is squeezed up between them as flames (1).
Question 26 · Spec F2, Key Idea 1 · Environments
State two features that distinguish desert (aeolian) sand from river sand. [2 marks]
Answer:
Any two from: very well sorted (1); well rounded, frosted grains (1); large-scale dune cross-bedding (1); red iron oxide coatings (1).
Question 27 · Spec F2, Key Idea 1 · Maturity
State what high compositional maturity shows about a sediment. [2 marks]
Answer:
Unstable minerals and rock fragments have been removed by weathering and transport (1); leaving mostly resistant quartz (1).
Question 28 · Spec F2, Key Idea 1 · Lithification
Explain the roles of compaction and cementation in lithification. [2 marks]
Answer:
Compaction squeezes grains together and reduces pore space as sediment is buried (1); cement, such as calcite or silica, precipitates from pore water and binds grains (1).
Question 29 · Spec F2, Key Idea 2 · Lava
Distinguish between aa and pahoehoe lava. [2 marks]
Answer:
Aa has a rough, jagged, clinkery surface (1); pahoehoe has a smooth, ropy surface (1).
Question 30 · Spec F2, Key Idea 1 · Graphic logs
State four features recorded on a graphic log. [4 marks]
Answer:
Any four from: bed thickness on a vertical scale (1); grain size (1); lithology (1); sedimentary structures (1); nature of contacts (1); fossils (1).
Question 31 · Spec F2, Key Idea 2 · Igneous structures
Explain why columnar jointing in basalt is not made of giant crystals. [2 marks]
Answer:
The columns are formed by contraction joints as the lava cools (1); the crystals within them are very small because cooling was fast (1).
Question 32 · Spec F2, Key Idea 2 · Igneous rocks
A coarse-grained rock contains quartz, feldspar and mica. Identify it and explain its crystal size. [2 marks]
Answer:
Granite (1); large crystals show slow cooling deep in the crust (1).
Question 33 · Spec F2, Key Idea 2 · Igneous rocks
Explain how gabbro, dolerite and basalt are related and how they differ. [2 marks]
Answer:
They have the same mafic composition (1); but are coarse, medium and fine grained respectively because of different cooling rates (1).
Question 34 · Spec F2, Key Idea 2 · Igneous rocks
State the mineralogy of peridotite. [2 marks]
Answer:
Mostly olivine (1); with some pyroxene and no feldspar or quartz (1).
Question 35 · Spec F2, Key Idea 2 · Igneous textures
Explain how a porphyritic texture forms. [2 marks]
Answer:
Large phenocrysts grow during slow cooling at depth (1); the remaining magma then cools quickly, forming a fine-grained groundmass (1).
Question 36 · Spec F2, Key Idea 2 · Igneous textures
Explain how vesicles form in lava. [2 marks]
Answer:
Gas bubbles come out of solution as pressure falls (1); and are trapped as the lava solidifies (1).
Question 37 · Spec F2, Key Idea 2 · Lava
State what pillow lavas show about the eruption environment. [2 marks]
Answer:
They form when lava erupts under water (1); and its surface is rapidly chilled into pillow-shaped lobes (1).
Question 38 · Spec F2, Key Idea 2 · Igneous structures
State two pieces of field evidence that distinguish a sill from a lava flow. [2 marks]
Answer:
A sill bakes the rocks above and below it, while a lava flow bakes only the rock below (1); a lava flow may have a vesicular or weathered top, and its upper contact is not chilled against overlying rock (1).
Question 39 · Spec F2, Key Idea 2 · Igneous structures
Distinguish between a dyke and a sill. [2 marks]
Answer:
A dyke is discordant and cuts across bedding (1); a sill is concordant and parallel to bedding (1).
Question 40 · Spec F2, Key Idea 2 · Volcanic hazards
Explain how a lahar forms. [2 marks]
Answer:
Water from heavy rain, melted ice or a crater lake mixes with ash and loose debris (1); forming a dense mudflow that travels rapidly down valleys (1).
Question 41 · Spec F2, Key Idea 2 · Magma generation
Explain how decompression melting occurs at divergent plate boundaries. [2 marks]
Answer:
Rising mantle experiences a fall in pressure (1); so its melting point (solidus) falls and it partially melts without extra heat (1).
Question 42 · Spec F2, Key Idea 2 · Volcanic hazards
Explain why viscous, gas-rich magma erupts explosively. [2 marks]
Answer:
High viscosity stops gas escaping easily (1); so pressure builds until the gas expands violently, shattering the magma into ash and pyroclastic flows (1).
Question 43 · Spec F2, Key Idea 2 · Metamorphism
Explain how metamorphism differs from melting. [2 marks]
Answer:
Metamorphism changes minerals and textures in the solid state (1); in response to changes in temperature, pressure or stress, without melting (1).
Question 44 · Spec F2, Key Idea 2 · Metamorphism
Compare the textures of contact and regional metamorphic rocks. [2 marks]
Answer:
Contact metamorphic rocks are non-foliated, such as hornfels, or show spots (1); regional metamorphic rocks are foliated, with cleavage, schistosity or gneissose banding (1).
Question 45 · Spec F2, Key Idea 2 · Metamorphic rocks
Name the parent rocks of marble and metaquartzite. [2 marks]
Answer:
Marble forms from limestone (1); metaquartzite forms from quartz sandstone (1).
Question 46 · Spec F2, Key Idea 2 · Metamorphic grade
Describe the sequence of rocks formed from mudstone with increasing regional metamorphic grade. [3 marks]
Answer:
Slate, with fine slaty cleavage (1); schist, with visible aligned micas (schistosity) (1); gneiss, with coarse light and dark bands (1).
Question 47 · Spec F2, Key Idea 3 · Deformation
Distinguish between elastic and plastic (ductile) deformation. [2 marks]
Answer:
Elastic deformation is recovered when the stress is removed (1); beyond the elastic limit, plastic deformation is permanent (1).
Question 48 · Spec F2, Key Idea 3 · Folds
Distinguish between a syncline and a synform. [2 marks]
Answer:
A synform is a fold that closes downwards, whatever the ages of the beds (1); a syncline has the youngest beds in its core (1).
Question 49 · Spec F2, Key Idea 3 · Faults
Identify a fault where the hanging wall has moved down relative to the footwall and state the stress that caused it. [2 marks]
Answer:
A normal fault (1); caused by tension (extension) (1).
Question 50 · Spec F2, Key Idea 3 · Unconformities
Describe the sequence of events that forms an angular unconformity. [3 marks]
Answer:
Deposition and lithification of the lower beds (1); folding or tilting, uplift and erosion (1); deposition of younger beds on the erosion surface (1).

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