Classification of mass movement according to cause, liquidity, speed of onset, duration, extent and frequency

what are landslides and rockfalls

a weakness point in a slope causes material above it to crash down at high speeds. land can be destabilised by heavy rainfall or earthquakes and can trigger tsunamis or block waterways to create lakes

what are mudflows

clay rich soil that is not bound by plant matter becomes saturated and flows. they behave like a liquid so often follow river valleys. lahars are a type of mudflow

what is soil creep

shear stress is not strong enough to cause a landslide or rockfall so land slowly inches forward over years or centuries

what are the three types of soil creep (3)

continuous, seasonal according to soil moisture, progressive in the build up to another mass movement

what is a slump

when a layer of a slope slips downwards. they form in sediment rich soils that behave as a coherent body

what is the role of gravity in mass movements

it is the initial force that pulls earth down or props it up

what is the role of pore pressure in mass movements

it destabilises slopes when it increases such as in saturated soil

what is the role of slope angle in mass movements

steeper slopes are more likely to trigger landslides

what is shear strength

how much the earth resists being moved

what is shear stress

the combination of forces encouraging earth to move

what are the two ways mass movements can be classified (2)

moisture, speed