Look closely at Oceano Dunes sand and you will see particles of various sizes and materials. These particles were eroded over time from the California coastline and inland coastal mountains and washed into the ocean. Ocean sand accumulated on the beach and was carried inland by winds to form coastal dunes. High winds blow the larger, heavier particles across the dune surface in a process known as saltation. This causes smaller, lighter particles to be broken off the larger ones. When wind speed is high enough the smaller particles are carried into the air and away in a dust plume. On an undisturbed dune, native vegetation and a natural surface crust limit the effect of wind, thereby stabilizing the dunes and limiting how much dust is carried into the air and away from the dunes. Intense vehicle activity in the Oceano Dunes SVRA has destroyed the natural fore-dunes and natural vegetation. Vehicle activity continually breaks up the natural crust throughout the riding areas. This has allows much more dust to be emitted from the dunes than would naturally occur. This fact has been proven by measurements and studies commissioned by the State Parks OHMVR Division and performed by the respected Desert Research Institute. In similar wind conditions, the active riding area of the SVRA emits a much more concentrated dust plume than the non-riding Oso Flaco area to the south, where the fore-dunes, natural vegetation and surface crust have been restored. The difference is clearly visible in the dust plume photograph above. The SVRA is just to the right of where the dust plume enters the picture. The vegetated dune area along the coast at the top of the picture shows no distinctly visible plume coming from that area. The Oceano Dunes SVRA is the only place in California where off-highway motor vehicle activity is permitted. No other coastal dune area in California emits PM10 in concentration as high as those from the Oceano Dunes SVRA active riding areas.