2B.6 Flashcards
What is a sub-aerial process?
Process that occur on the cliff face rather than the cliff foot.
Are mass movements and weathering sub aerial processes?
Ye at coasts
What is weathering?
The breakdown of rocks in situ by mechanical, chemical or biological agents.
How is weathering different from erosion?
Because erosion is rather the breakdown and removal of rock by an external agent (winds/waves/rivers/ice)
What are mass movements?
The movement of rocks/sediment downslope due to gravity.
How are weathering and mass movements linked?
Weathering often triggers many mass movements.
What influences how vulnerable a cliff is to mass movements?
Lithology and structure of a cliff
Weathering processes = loosening of cliff faces
Water = saturate soil or not?
Angle of slope
What are the types of weathering?
Mechanical (physical)
Biological
Chemical
What are types of mechanical weathering?
Freeze thaw
Salt crystallisation
Wetting and drying
What are the types of chemical processes?
Carbonation
Oxidation
What are the types of biological weathering?
Plants roots
Rock boring
Seaweed acids
What is freeze-thaw weathering?
Water into cracks freezes expands (9%) causing pressure into rocks cracking them apart. Most vulnerable are well jointed rocks.
Happens in fluctuating temperature areas. And is repeated. Can cause large rock falls on jagged cliff faces.
What is salt crystallisation weathering?
Water spray hits cliffs which gets into cracks evaporates leaving salt which expands exerting pressure breaking apart well jointed rocks ie Limestone happening in hotter climates. This creates scree at cliff foots.
What is wetting and drying weathering?
Rocks rich in clay expand when wet and contract when dry which repeats causing them to spit. This makes the cliff vulnerable to slumping.
What is carbonation weathering?
Rocks ie limestone being slowly dissolved as it reacts with weak carbonic acid in rainwater. This widens gaps on flat surfaces ie wave-cut platforms making them vulnerable to other processes
What is oxidation?
When oxygen mixes with iron in a rock causing it to rust making rocks weaker ie sandstones and shows are vulnerable. This causes crumbling because of weak intermolecular links.
What is plant root weathering?
Roots growing into cracks slowly widening areas which can be effective on vegetated faces. Ie trees being removed = destabilised. This leads to rock falls
What is rock boring weathering?
Small scale organisms dig into rocks secreting acids that dissolve rocks. Sedimentary rocks are vulnerable as they are weaker. Holes make it vulnerable to further weathering
What is seaweed acids weathering?
When plants ie kelp contain acids ie sulphuric acids which can burst into rocks dissolving them. This can lead to crumbling..
What are the types of mass movements events?
Rock falls or talus slopes. Rotational slumping Flow Block falls Soil creep
What are rock falls mass movements?
When freeze-thaw weathering gets int steep slopes (75°) only a rock
What is rotational slumping mass movements?
Unconsolidated rock is impermeable and malleable allowing slip lanes which are curved by having low pore pressure.
What is flow mass movements?
Saturated soil is exceeded infiltrated soil leading to release of water causing leakages.
Clay becomes softer (wetting and drying)
What are block falls mass movements?
In jointed rocks planes are parallel to slopes.
More water reduces friction which increases sliding
In some events rocks can slide over underlying rocks
What is soil creep mass movements?
When there is a slow continual process that soil individual particles move downhill due to gravity
