Wind erosion and sediment loss

As the name suggests, wind is the transport agent in wind erosion. The speed of the wind must surpass a threshold in order to move sediments (called the Friction Threshold Velocity). Large particles (>90µm) are usually the first particles to move, hopping along the soil surface. Each time a large particle bounces off the surface, more sediment is disturbed and released into the airstream, a bit like an avalanche.

The smaller particles are lighter and therefore can be held a lot higher aloft. It is this fine fraction (particles <20µm) which is called ‘dust’ and can travel a great distance in the air. Australian dust has been tracked to New Zealand and Antarctica. Dust also contains a lot of soil nutrients (organic matter and clay) thus depleting the nutrients at the source (where the dust originated) and enriching nutrients at the sink (where the dust is deposited). For example, oceanic dust deposits are an important source of nutrient iron for marine organisms.
Measuring sediment loss is problematic. A dust event could encompass one paddock, or paddocks across the entire eastern Australia. Measurement of how ‘deep’ (high) the dust plume extends is difficult, relying on meteorological studies or observations from airplane pilots.