Rain, wind and ice constantly wear down the Earth's land surface and transport the resulting broken down rock and soil to the oceans in a process called erosion.
Left unchecked, erosion would transport all the Earth's dry land into the oceans, leaving a water world. It is only the movement of the Earth's plates, which builds mountains, that stops this happening.
Geologists are quite precise about what erosion is: The term erosion only covers the transportation of Earth materials. Rock and soil are altered while still in place by a process referred to as weathering. Weathering often makes rock and soil susceptible to erosion.
Image: The wind eroded ridges in this image are known as yardangs. These examples are in the Dasht-e Lut desert, Iran. (credit: George Steinmetz/SPL)
Dramatic footage from the centre of the storm demonstrates the abrasive force of sand.
Two of the major challenges of filming a sand storm are keeping the equipment (and the crew) from being sand-blasted and getting the light right. In order to make the storm appear as impressive on film as it does in reality, the light needs to hit the sand storm at the right angle making position and time of day critical. It took 3 weeks and 10 storms to get these shots.
Timelapse illustrates the erosive power of wind as it creates weird rock formations.
A combination of specialist tracking timelapse and digital stills photography captured these dramatic scenics as marble towers are sand-blasted into ever more bizarre shapes by desert winds.
A beautiful rock formation in Arizona shows the wind's power.
Dr Iain Stewart visits The Wave, a rock formation in Arizona sculpted by the wind. This beautiful place is an important illustration of how the wind shapes the Earth.
Wind transports large amounts of nutrient-rich dust around the planet.
Dr Iain Stewart explains how wind transports large amounts of nutrient-rich dust around the globe. This dust fertilizes the oceans and plants on land.
Shifting continents caused the Mediterranean to dry out.
Dr Iain Stewart explains how, six million years ago, the continents of Europe and Africa moved together and cut off the Mediterranean Sea. He also explains how rivers erode the land and bring salt to the oceans.
In geomorphology and geology, erosion refers to the actions of exogenic processes (such as water flow or wind) which remove soil and rock from one location on the Earth's crust, then transport it to another location where it is deposited. Eroded sediment may be transported just a few millimetres, or for thousands of kilometres.
While erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. Excessive (or accelerated) erosion causes both 'on-site' and 'off-site' problems. On-site impacts include decreases in agricultural productivity and (on natural landscapes) ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the eventual end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of water bodies, as well as sediment-related damage to roads and houses. Water and wind erosion are now the two primary causes of land degradation; combined, they are responsible for about 84% of the global extent of degraded land, making excessive erosion one of the most significant environmental problems world-wide.
Intensive agriculture, deforestation, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion. However, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils.