On meeting the surface, the sand is projected up to several hundred metres into the atmosphere due to the large pressure changes involved on meeting the surface. 99% of the water from the mixture is lost by this point due to perspiration which results in a thick sandy cloud which rises above and can be seen from several miles away. The San Pedro-Pellado volcanic eruption in Chile however produced a sand cloud which was seen as far away as Georgia (not the American one, but the real one in Europe) which shows just how violent such eruptions can be.