Physical processes and landscapes
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Define weathering (in a desert).
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All Flashcards in Topic 9.2
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9.2.112 cards
Define weathering (in a desert).
The breakdown of rock **in place** (no transport), by heat, salt or chemical action.
What is aeolian action?
**Wind** action - the wind **erodes** (abrasion, deflation), **transports** and **deposits** sand.
Define abrasion (wind).
Wind-blown sand **sandblasts** rock, wearing it away - strongest near the ground where most sand is carried.
Define deflation.
Wind **lifts and removes** loose sand, lowering the surface into a hollow or leaving desert pavement.
How does a sand dune form?
By **aeolian deposition** - wind carrying sand slows or hits an obstacle and drops its load; the dune then migrates.
Two desert weathering processes?
**Exfoliation** (heating/cooling peels off layers) and **salt crystal growth** (crystals prise rock apart); also granular disintegration, hydrolysis.
How does a rock pedestal form?
Wind **abrasion is strongest near the ground**, wearing the base thin while the top survives - a mushroom shape.
Name a water-formed desert landform + process.
An **alluvial fan** - a flash-flooded channel leaves the mountains, slows, and deposits a fan of sediment.
What controls which sand dune forms?
The **sand supply, wind (strength/direction) and vegetation** - read off the triangular graph.
Why does vegetation matter for dunes?
It **slows the wind** and roots **bind the sand**, so sand is deposited and the dune is anchored.
Wind vs water - which makes what?
**Wind**: dunes, pedestals, yardangs, deflation hollows. **Water**: wadis, alluvial fans, playas, mesas/buttes.
What does a top [10] water-vs-wind essay need?
Two+ landforms tied to processes, **named deserts**, a weighing of water vs wind (incl. over time), and a clear judgement.
9.2.212 cards
Define permafrost.
Ground that stays **frozen for two or more years**; the surface **active layer** thaws each summer.
What is freeze-thaw weathering?
Water freezes in rock cracks, **expands ~9% and shatters** the rock into angular fragments.
Define plucking.
Meltwater freezes onto rock and the **moving ice pulls it away**, eroding the glacier bed.
Define abrasion.
Rock frozen into the ice **grinds the bedrock smooth**, like sandpaper.
What is solifluction?
The waterlogged **active layer creeping slowly downslope** over frozen ground in summer.
What is mass balance?
The balance of **accumulation (snow gained) vs ablation (ice lost)** — it decides if a glacier advances or retreats.
How does a corrie form?
Snow collects in a hollow -> freeze-thaw + **plucking** steepen the back wall -> **abrasion** deepens the floor -> a rock lip + **tarn** remain.
Why do most corries face north/east?
Those slopes are **shaded and coldest**, so snow survives longest and ice can form and erode there.
Name three periglacial landforms.
Patterned ground (frost heave), **solifluction lobes**, and **pingos** (ground-ice domes).
Why does permafrost make Arctic extraction hard?
Heat **thaws the frozen ground**, which subsides and weakens, so pipelines fracture and foundations tilt.
Glacial vs periglacial — the difference?
**Glacial** = moving ice erodes (plucking/abrasion); **periglacial** = freezing/thawing of water in permafrost builds landforms.
What does a top [10] glacial essay need?
Named landforms developed (corrie, arete, trough), a real example, a weighing of the processes, and a clear judgement.
Topic 9.2 study notes
Full notes & explanations for Physical processes and landscapes
Geography exam skills
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