weathering, mass movement and runoff

What is weathering?

The breakdown or disintegration of rock in situ or close to the ground surface

What does weathering lead to as a process?

The transfer, flow, of material

When does positive feedback operate with weathering?

If the rate of debris removal exceeds the rate of weathering and mass movement

When does a negative feedback occur with weathering?

If debris removal is slow and ineffective, lead to a build up of an apron of debris (scree) that reduces the exposure of the cliff face as it extends up the cliff face.

What is mechanical weathering?

The break up of rocks without any chemical changes

What is frost shattering/freezethaw?

When water enters a crack or joint in the rock when it rains and freezes. Expands in volume forcing crack to widen and fragments of rock break away, collect at the base of cliff as scree.

What is salt crystallisation?

Water evaporates salt crystals left behind which can grow over time and exert stress on the rock causing it to break up, can also corrode rock

What is biological weathering?

The breakdown of rocks by organic activity

What are examples of biological weathering?

Plant roots grow into cliff face, water running through decaying vegetation becomes acidic, birds,

What is chemical weathering?

Chemical reaction where salts may be dissolved or a clay like deposit may result which is then easily eroded

What is carbonation?

Rainwater absorbs carbon dioxide from the air to form a weak carbonic acid, reacts with calcium carbonate in rocks to form calcium bicarbonate which is easily dissolved. Cooler the temp of rainwater, the more carbon dioxide is absorbed

What is oxidation?

The reaction of rock minerals with oxygen to form a powder leaving rocks more vulnerable to weathering

What is solution?

The dissolving of rock minerals

What is mass movement?

The downhill movement of material under the influence of gravity

What is soil creep?

Extremely slow movement of individual soil particles downhill. Precise mechanisms of movement often involves particles rising towards ground surface due to wetting or freezing and then returning vertically to the surface in response to gravity as the soil dries out or thaws. Zigzag movement similar to longshore drift.

What are mudflows?

Involves earth and mud flowing downhill. Water gets trapped in the rock increasing loss water pressure, forcing rock particles apart and leads to slope failure. Often sudden and fast flowing

What is a land slide?

Block of rock moving rapidly downhill along a planar surface. Moving material becomes mixed, frequently triggered by earthquakes or very heavy rainfall

What is a rockfall?

Sudden collapse or breaking away of individual rock fragments, steel or vertical cliffs. Often triggered by mechanical weathering

What is a landslip or slump?

The slide surface is curved rather than flat, occur in weak and unconsolidated clays and sands often when permeable rock overlies impermeable rock causing a build up of pore water pressure

What is runoff?

When overland flow occurs down a slope or cliff face small particles are moved downslope to enter the littoral zone. Transfers both water and sediment between natural systems

What is solifluction?

Similar to soil creep but specific to cold periglacial environments