weathering Flashcards
define weathering
it is an exogenic force that is responsible for shaping the landscape on the earths surface
what are the types of physical weathering
freeze thaw action
exfoliation
what is nessicary for freeze thaw action to occur
adequate supply of water
rock has pre existing fractures or joints
tempretures regulary rise and fall above freezing
desrcibe the process of freeze thaw action
in the day rain water seeps into cracks /joints
in the night it freezes- widening the crack
water expands 10%
causes stress on crack or joint
in the day it melts ice and the water seeps deeper into the joint/crack
repeated freeze thaw cycles enlarge
rocks break apart forming scree
by how much does water expand when it turn to ice
10%
what is exfoliation
it is the process by which layers of rock are peeled away due to repeated expansion and contraction. Occurs in regions with a large diurnal range
what is a diurnal range
it is the difference between the lowest and highest daily tempreture range - desert
explain exfoliation process
in the day tempreyures in the desert exceed 40 degrees cuasing outer layers of rock to expand
as temps fall in the night the outer layers contract
repeated expansion and contraction weaken the outer layers so they crack and peel away layer by layer over repeted heat cycles
what are the types of chemcial weathering
carbonation
hydration
oxidation
hydrolysis
what rock does carbonation effect
limestone and chalk
calcium carbonate rocks
what is hydrolysis
reaction between minerals in rock and acidic rain water
descirve the process of hydrolysis
minerlas in the rock like feldspar turn softer into a weaker materical of kaolin clay due to the carbonic acid in rain. It turns it tinto kaloin which doesnt bond well and breask down easily.
It causes more resistant materiers like quartzite to move down hill
what kind of rock mineral is affected by hydrolysis
feldspar turns into kaolin clay
what increases the rate of hydrolysis
wetter and warmer climates
what is oxidationr
reaction between oxygen and minerals in the rock
describe the process of oxidation
oxygen is disccolved in water and reacts with metals in rock usually iron. It produces oxide susually iron oxide which gives rocks a reddish colour. It is eefective in breaking down basalt as it has a high iron content
what is hydration
is the absorbtion of water by rock minerals
describe the process of hydration
when minerlas absorb water they exapnd which cuases stress in the rocks. It cuases them to fracture and shatter as they become hydrated. Shale is very prone to this
what climate would be prone to hydration
humid climate
what is doming
as overlying materials are rmeoved there is less pressure on underlying rock
as the underlying layers expand the overlying layers fracture and form scree
the expanding layers lead to the formation of a dome mountain
what is block disintegration
in desrts sometime freeze thaw action happens in the night and exfoliation in the day leading to more rapid weathering, causing rock to break into large rectangular blocks (block disintegration)
what is chemical weatehring
it is the breakdown of rock through decomposition caused by chemical reactions between rock minerlas and the earths environment
