Mass Mass MovementMovement

MudflowMudflow

Angle of slope > 10°

Start of Mudflow Toe marks final resting place

•Input of precipitation above the hollow increases weight and lubrication of topsoil

Diagram of Mudflow

Downslope movement of saturated soil lobe

Description of MudflowDescription of Mudflow

Flows take place gradually, possibly faster at one time in the year than another

Encouraged by wet winters mudflows emerge from the base of a rotational slip and slowly spread and pour over earlier, lower slips and flows into the sea.

Mudflow can travel extremely fast at more than 10ft/s.

An example of mudflowAn example of mudflow ‘‘I saw a great mass of upper Greensand densely I saw a great mass of upper Greensand densely

covered with bushes and trees slowly crawling covered with bushes and trees slowly crawling downwards from the highest terrace, while below a river downwards from the highest terrace, while below a river of liquid mud was slipping over the low cliff above the of liquid mud was slipping over the low cliff above the beach…the main movement in the night must have been beach…the main movement in the night must have been very rapid, as by daylight a huge fan of debris, crested very rapid, as by daylight a huge fan of debris, crested with uprooted trees, had pushed across the beach to with uprooted trees, had pushed across the beach to beyond the low water neap tides.’beyond the low water neap tides.’

Source: Quoted in D. Brunsden and A. Goudie:Source: Quoted in D. Brunsden and A. Goudie:

Classic Coastal Landforms of DorsetClassic Coastal Landforms of Dorset

Conditions for mudflowConditions for mudflowMaterials involved:

• A mixture of mud and water

•Soil and rock

Conditions needed:

•Heavy rainfall for long period of time

•Both gravity and slope angle play a part

•Slope angle must be greater than 10°

Vegetation and human factors:

•There are no human factors

•Soil becomes saturated

Mudflow

Cows