Weathering and the River Valley Flashcards
Define weathering
The breakdown of rocks in situ
Name three types of weathering
Mechanical, Chemical and Biological
Define mechanical weathering
Breakdown of rocks without changing its chemical composition
Define biological weathering
Break down of rocks by living things
Define chemical weathering
Breakdown of rocks by changing its chemical composition
Example of Mechanical weathering
Freeze - Thaw weathering
Example of biological weathering
Plants roots break down rocks by growing into cracks and pushing them apart.
Example of chemical weathering
Carbonation
Define carbonation weathering
A type of chemical weathering. Rain water has carbon dioxide which makes it weak carbonic acid. Carbonic acid reacts which rock containing calcium carbonate such as limestone. The rocks are then dissolved by the rain water.
Define freeze thaw weathering
It occurs when temperatures alternate below and above 0 degrees. Water gets into rocks with cracks. When the water expands it puts pressure on to rock. When it water thaws it release pressure on to the rock. Repeated freezing and thawing widens the crack and causes the rock to break up.
Define course
The path of a river as it flows downhill
Name the three different courses of the river
Upper course, middle course and lower course. With upper nearest to source and lower nearest to mouth (ending) of river.
What happens when you go down a river (upper course to middle course to lower course)?
. Gradient goes from steep to medium to gentle
. V shaped valley becomes wider and less steep
. Channel becomes deeper and wider
Define channel
The water in a river (refer to diagram on CGP book.)
Name two types of profiles
Long profile and short profile
