Mass Wasting: Weathering, Erosion and Transport
From the remarkable process of plates colliding and building mountains. They are only to be dismantled by mass wasting.
By mostly water, wind and ice, mass wasting is the removal of rock due to erosion. Then, it involves the transport of sediments downhill due to gravity.
Currently, Mount Everest is thrusting upwards faster than it being eroded away. But in hundreds of millions of years time, erosion could take its toll shortening it by millimeters each year.
Another example is the Appalachian mountains which used to be 5 miles higher when Africa first collided with North America. But over 300 million years, weathering and erosion have torn them down and washed them through streams.
Mechanical, chemical and biological weathering
Weathering is the breakdown of rocks into sediments. At the same time, mechanical, chemical and biological weathering all partake in eroding rocks.
First, mechanical weathering involves erosion by physical means. For instance, freeze-thaw and exfoliation from temperature change are examples of mechanical weathering.
Second, chemical reactions can transforms a rock’s composition through chemical weathering. Most likely, this process either dissolves the minerals or converts them into other minerals.
Finally, biological weathering involves the removal of rock due to living things. For example, burrowing animals can disturb soils and rocks. Or lichen form a symbiotic relationship between fungi and algae releasing chemicals.
Surface runoff and transportation
For the water that precipitates on the land, it eventually flows back into the ocean. Minerals get washed away and transported to an outlet at the nearest ocean.
We all live in a watershed. Watersheds are like upside-down umbrellas with well-connected networks of tributaries. They zig-zag all the way to a main body of water like a river or lake. So this means that everything upstream ends up downstream.
Runoff transports minerals and salts from the surface so this is why oceans are salty and lakes and rivers have freshwater.