paper 1

river processes, natural hazards unit

Erosion

A process which wears away and removes material by a force such as wind, water or air

Hydraulic action

The force of the river against the banks can cause air to be trapped in cracks and crevices casuong the rocks to break apart. The pressure weakens the banks and gradually wears it away.

Abrasion

When rocks grind along the river bank and bed chipping away at solid rock, creating small particles that can be carried along and smooth out the bed and banks.

Solution - erosion

When the water dissolves certain types of rocks e.g. limestone

Attrition

When rocks that the river is carrying knock against each other. They break apart to become smaller and more rounded

Lateral erosion

Sideways erosion by a river on the outside of a meander channel. It eventually leads to the widening of the valley and contributes to the formation of the flood plain.

Vertical erosion

Downward cutting action of a river that deepens its bed, often forming a V-shaped valley.

Transportation

Eroded material is moved from one place to another

Traction

The rolling of boulders and pebbles along the river bed.

Saltation

Small pebbles and stones are bounced along the river bed

Suspension

Lighter sediment is suspended (carried) within the water

Solution - transportation

The transport of dissolved chemicals

Deposition

River loses energy and drops sediment

natural hazard

natural event which interacts with people

tectonic hazard

movement of tectonic plates

atmospheric hazard

changes in weather conditions and pressure

geomorphological hazard

changes on the earths surface (landslides)

biological

involving living organisms(wildfires)

earthquake

vibrations of the earths lithosphere due to tension release processes

mercalli scale

subjective and measures the damage and is I - XII

richter

scientific and measures the magnitude, the scale is logarithmic so each stage is 10x worse than the last (1-10)

primary effects

effects that occur immediately as a direct result of the event

secondary effects

subsequent effects of the event but can be more devastating

immediate responses

responses undertaken immediately or in the hours and days after the event

long-term responses

responses undertaken in the weeks, months and even years after the event

Global Circulation model

cells of air redistributing heat around the earth so the poles dont get too cold and the equator doesnt get so hot