Key Idea: Topic 9.1 is about what makes an environment 'extreme' — physical conditions so harsh that life and human use are very difficult. It pulls together two opposite kinds of extreme place: 9.1.1 — hot, arid & semi-arid: hot deserts (under ~250 mm of rain a year) and their semi-arid margins (~250-500 mm), where a permanent water deficit dominates — caused by sub-tropical high pressure, rain shadows, cold ocean currents and continentality. 9.1.2 — cold & glacial: glacial environments (under ice — ice sheets, mountain glaciers) and periglacial ones (frozen ground, permafrost with an active layer that thaws each summer), clustered at high latitudes and altitudes. This is Option C content, examined on Paper 1 — SL answers 2 options, HL answers 3 (same questions). Each option pairs a data-response read off a map/graph with short structured parts, then a [10] extended answer (Examine/Evaluate/Discuss).
🏜️ 9.1.1 — Hot, arid & semi-arid environments
Hot deserts have a permanent water deficit — far more potential evaporation than rainfall. Semi-arid margins get a little more rain but it is low, seasonal and unreliable, bringing drought and flash flooding. Both are extreme because water is scarce and undependable. The skill examiners test is reading a distribution map or climate table, then naming a real desert and the process that dries it.
Tip: On a distribution map or climate table, the driest site has the lowest annual rainfall and usually the largest day-night range. Read the key first, quote the units, then anchor your explanation to a named desert and its process — never just 'a desert'.
❄️ 9.1.2 — Cold & glacial environments
Glacial environments are under ice — ice sheets (Antarctica, Greenland) and mountain glaciers (the Alps). Periglacial ones are not under ice but stay frozen: they have permafrost, with a thin active layer that thaws each summer (Siberia, Alaska, northern Canada). In the data-response you Describe a distribution by latitude + compass direction, Estimate a value off a cross-section or segmented diagram, and State / calculate exact figures.
[Diagram: geo-bar-chart]
Estimate means read a value off the figure within a tolerance (e.g. about 21%). State means give the exact value shown (e.g. Arctic sea ice lost the most, ~31%). For a difference, read both values and subtract. Always describe a location by latitude and compass direction, never longitude alone.
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Exam Tips
- Option C sits on PAPER 1: SL answers 2 options, HL answers 3 — each is a data-response + short structured parts, then a [10] extended answer.
- Hot desert = under ~250 mm/yr; semi-arid = ~250-500 mm/yr. Deserts dry from sub-tropical highs, rain shadows, cold currents or continentality.
- Always name a REAL place and its process — Sahara/Sahel, Atacama, Arabian, Outback; Antarctica, the Arctic/Alaska, the Alps.
- Glacial = under ice; periglacial = permafrost (active layer thaws in summer). Describe location by latitude + compass, never longitude alone.
- Estimate = a sensible read off a figure within tolerance; State = the exact value shown. For a difference, read both and subtract.
- On the [10] Examine/Evaluate, weigh a counter (other characteristics, unreliability) and finish with a clear judgement.