I don’t know the Greek for this phenomenon but occasionally in the Spring, atmospheric dust carried aloft across the Mediterranean from North Africa, is brought to earth by rainfall. That happened this morning at dawn, and we awoke to muddy mess on our balconies. Obviously dirt that remains in the atmosphere for thousands of miles and across a body of water as big as the Med is powder-fine, and it makes a sort of mud that settles in the smallest niches.
greekdreaming 
That dust is nasty stuff. It often drifts west to the Caribbean Sea. It presents a health hazard like smog to people and also to coral. The dust contains minerals and microbes. African Locusts have even been known to be carried across the Atlantic on that wind to the Caribbean! The Puerto Rican weather reports will announce if there is a danger present for activities outdoors due to the stuff. A principle problem with that dust is that, by the time it crosses the Atlantic, only the very fine particle remain and those are easily ingested.
Here is a USGS link to more info: http://gallery.usgs.gov/videos/223#.T5G8So63I7A
Thanks for this. From my vantage point here, I’d had no idea the dust had been studied at all.