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All 12 Flashcards — Mass movement processes
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Question
Define mass movement.
Answer
The **downhill movement of rock, soil and debris under gravity**, when the driving force beats the resisting force.
Question
What is slope stability?
Answer
How resistant a slope is to failing — high friction and strong material make a slope stable.
Question
What is a slip surface?
Answer
The curved or flat plane along which material **breaks away and moves** during a mass movement.
Question
Primary vs secondary hazard?
Answer
A **primary** hazard is the original event (e.g. an earthquake); a **secondary** hazard is one it triggers (e.g. a rock fall).
Question
Which mass movement is the slowest?
Answer
**Soil creep** — only millimetres a year; spotted from tilted poles, curved trunks and terracettes.
Question
Which mass movements are fastest / wettest?
Answer
**Debris flows** (very high water content) and **rock falls** (very fast) — both move almost instantly.
Question
Why does water content speed a mass movement?
Answer
Water **adds weight** and **lubricates the slip surface**, lowering friction, so material moves faster.
Question
Two physical factors that speed mass movement?
Answer
Water content and gradient (also sediment size, geology and bare vegetation).
Question
Two human activities that destabilise a slope?
Answer
Undercutting the base and deforestation (also building, waste heaps, disturbing drainage).
Question
When is a rock fall a secondary hazard?
Answer
When it is **triggered** by another event — an earthquake or heavy rain dislodging loose cliff blocks.
Question
Name a real triggered mass-movement disaster.
Answer
Nevado del Ruiz 1985 lahar (Armero), or the Vargas 1999 debris flows, Venezuela.
Question
What does an Outline [2] answer need?
Answer
A valid factor (1 mark) **plus** development of how it works — the mechanism (1 mark).
Read the notes
Full study notes for Mass movement processes
Topic 10.1 hub
Geophysical systems
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Geography exam skills
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