Chapter 7 - Mass Movement

Question 1

Mass movement

Answer 1

Is the movement of loose earth materials (soil, stones, mud(regolith)) down a slope under the influence of gravity.

Question 2

Causes of mass movement

Answer 2

Slope - the steeper, the faster
Water - makes soil heavier, acts like a lubricant
Lack of vegetation - roots of plants hold soil in place
People - digging and drilling disturbs ground

Question 3

Soil creep

Answer 3

Slow mass movement. Caused by water and gravity. Faster at surface, slower deep down

Question 4

Evidence of soil creep

Answer 4

Fences and trees bend downhill
Terracettes (natural steps) form
Walls collapse from pressure of soil behind them

Question 5

Landslide

Answer 5

Rapid movement of loose rock and soil down a slope.
Caused by undercutting (wearing away of material at the base), coastal erosion and earthquakes.
Heavy rain loosens soil -> landslide
Buildings can be buried
People can be killed
Roads blocked off so it’s hard to get help

Question 6

Coastal cliff collapse

Answer 6

Waves wear away the base causing it to collapse

Question 7

Bogbursts

Answer 7

Fast movements of bog down a slope.
Loosened by heavy rainfall or work on mountaintop wind turbines when vegetation is removed
Like a river of turf or peat flowing down a hill

Question 8

Mudflows

Answer 8

Fast movements of mud down a slope

Caused after heavy rainfall or volcanic activity

Question 9

Lahar

Answer 9

When lava melts snow to make a river of mud

Question 10

Case study mudflow

Answer 10

Nevado del Ruiz is snow covered volcanic mountain in Columbia.
Erupted in 1985 and hot ash and rocks melted the snow
Water picked up soil and rocks to form lahars
23,000 people were killed when the lahar in the Lagunilla River destroyed the town and 5000 homes were covered