geomorphic processes Flashcards
what is weathering?
in a glacial areas some types of weathering are particular significant and therefore influence the formation of glacial landforms
uses heat energy to produce physically or chemically altered materials from surface or near surface rock
what is physical weathering?
The breakdown of rocks without chemical change. Usually, this is caused by abrasion.
what is freeze thaw weathering?
Water enters cracks/joints and expands by 10% when it freezes. In confined spaces this exerts pressure on the rock, causing it to split or pieces to break off, even in very resistant rocks
the more frequent the more effective the process will be
what is frost shattering?
at extremely low temps, water trapped in rock pores freezes and expands
this creates stress which disintegrates rock to small particles
what is pressure release?
when the weight of overlying ice in a glacier is lost due to melting, the underlying rock expands and fractures parallel to the surface
this is significant in the exposure of sub-surface rocks such as granite and is also known as dilation
parallel fracture sometimes called pseudo-bedding planes
what is chemical weathering?
decomposition of rock caused by chemical reactions between elements of the weather and some minerals within the rock.
may reduce the rock to its chemical constituents or alter the chemical and mineral composition of the rock
what do chemical weathering processes produce?
weak residue of different material that may then be easily removed by erosion or transportation processes
what does the temperature do to chemical reaction?
the rate of most chemical reactions are faster when the temperature is higher
where are most chemical weathering processes more effective?
in warm or hot climates and regions
how do some weathering processes effect the atmosphere?
when rocks are in contact with weakly acidic water
one issue with climate change and increasing levels of atmospheric CO2 is that rain and therefore ice is becoming more acidic
what is oxidation?
a chemical process that weathers certain types of rock and involves the absorption of oxygen from either the air or water by rock minerals
what is carbonation?
Rainwater absorbs CO2 and forms carbonic acid. The acid dissolves alkaline rocks such as chalk, creating calcium bicarbonate which is washed away in the solution.
is reversible
what is a solution?
the chemical weathering process by which rock minerals are dissolved
what is hydrolysis?
a chemical reaction between rock minerals and water
silicates combine with water producing secondary minerals such as clays
what is hydration?
water molecules added to rock minerals create new minerals of a larger volume
can cause surface flacking in many rocks, partly because some minerals also expand by about 0.5% during the chemical change as well because they absorb water
what is biological weathering?
the breakdown of rocks through the chemical and physical action of living organisms e.g growth of plant roots
why is plant and animal activity limited by glacial landscapes?
low temperatures
what is the effect of tree roots?
grow into cracks or joints in rock and exert outward pressure
similar effects to freeze-thaw
when trees topple their roots can exert leverage on the rock and soil, bringing them to the surface and exposing them to further weathering
what are organic acids?
produced during the decomposition of plant and animal litter cause soil water to become more acidic and react with some minerals in a process called chelation
what is chelation?
a type of chemical weathering caused by acids derived from rainwater and dead organic material
what is mass movement?
The downhill movement of weathered material due to the force of gravity
what is the most significant mass movement process?
the most significant mass movement processes are those acting on steep slopes which lead to the addition of material to the glacier below, loading it with debris and providing the tools of abrasion
what is rock fall? (mass movement)
on slopes of 40 degrees or more, especially if the surface is bare, rocks may become detached from the slopes by physical weathering processes
these fall to thee foot of the slope under gravity and then transport processes may then remove thus material or it may accumulate as a relatively straight, lower angled slope
what are slides in mass movements?
-may be linear with movement along a straight line slip plane such as a fault or a bedding plane between layers of rock, or rotational slip with the movement taking plane along a curved slip plane
-rotational slides are also known as slumps
how can slides occur in glaciated landscapes systems?
slides may occur due to steepening or undercutting of Valley sides by erosion at the base of the slope, adding to the downward forces
