As our learning objective mentioned earlier, Earth's surface is constantly changing. Many processes change Earth's landscape instantaneously, right in front of our very eyes, while others take place gradually, over time. Erosion and weathering are just a couple of examples of these slow processes.
Erosion is the process by which soil, rock or other surface substrate is transported across Earth's surface by natural processes such as wind, water or gravity, and deposited elsewhere.
- Water collected on a surface congeals, flows and washes away topsoil, creating sheet erosion
- Water is also an erosion agent in streams or rivers where it transports particles downstream, cuts the channel deeper with water flow, cuts the channel wider with water flow, and erodes a channel up-slope from the source of the headwaters.
- Wind erosion refers to the power of blowing particles to erode rocks and sand.
Weathering is a process that often acts along with erosion to help shape Earth's surface. While erosion is the process that transports the particles, weathering is the process that creates the particles . Weathering is when nature breaks rocks and soil down into smaller particles, or changes the actual composition of the landscape. Weathering can be physical, chemical or biological.
- Physical weathering is when rock is broken down through Earth's natural processes. An example of physical weathering is when water seeps into the cracks of rocks, freezes into ice, and therefore expands forcing the rock to break.
- Chemical weathering is when reactions between two things cause a change in rocks composition (what something is actually made of). An example of chemical weathering is when acid rain dissolves underground rock, causing it to collapse and make a hole in Earth's surface.
- Biological weathering is when animals or other living organisms cause a breakdown of rock or change in the composition of rock. An example of biological weathering would be an animal digging a burrow, causing an increase in pressure and nearby rock to break.