Physical Weathering Of A Rock Flashcards
Name the 3 types of physical weathering
Freeze-thaw action
Onion weathering (exfoliation)
Crystallisation of salts
Give 3 characteristics of physical weathering
Weathering is an exogenic force (happens on the surface)
The chemical composition does not change
Mechanical weathering breaks down rocks into smaller pieces called regolith
What is regolith
The smaller rocks formed from mechanical weathering
How does physical weathering break down rocks
It’s puts rocks under great pressure causing them to break and split apart
Where can freeze-thaw action be seen
Swiss alps and comeragh mountains Co.Waterford
Explain how freeze-thaw action occurs
During day rainwater seeps into cracks of rock
It freezes at night and expands by 10%
Over time this weakens the rock and shatters it
What happens to the rock after freeze-thaw action
The regolith will move down the slope under the influence of gravity this is known as mass movement
The weathered rock is known as scree and will gather at the foot of the slope
What is a benefit of scree
It can protect the lower slopes of the mountain from further weathering
Where does freeze-thaw action usually occur
In areas where temps vary above and below freezing point
Artic and temperate zones such as Ireland and mountain tops
Also places where water is present
How much does the water expand by and what does this expansion do
It expands by 10%
This puts the rock under great pressure and enlarges the expansion
What happens during the day when the water melts
The pressure is released
Where does exfoliation take place
In hot dry climate where temp difference between day and night Varys greatly (diurnal range)
Give an example of a place where exfoliation takes place
Arizona where temps vary from 50 during day to below 0 at night
Explain how exfoliation takes place
> extreme heat causes rock to expand
when the rock cools it contracts
this leads to the outer layers of the rock to shatter
What happens to the rocks that have shattered from exfoliation
They drop to the ground and collect at the base of the rock where they form scree
This scree is then weathered
