Also, the heavier dust particulates generally do not get as high in the air leaving the finer particulates up high. Furthering the idea that by moving the intake up higher less dust is making it to the air cleaner, and the dust that does is make it to the air cleaner is finer and potentially less damaging to the air cleaner. Dust will still make it in, just less of it. My first run out in the desert after I got my Tacoma was with the factory air cleaner (it was new). I was out in the desert for about 3 hours following another truck. The air cleaner was completely clogged with dust and needed to be replaced by the time I got home. Later after adding a snorkel I went on a 4 day 1000+ mile trip across the entire state of Utah on dirt roads with 5 other trucks. Lots of dust the entire trip. When I got home and checked the air cleaner it was a little dusty but not bad at all. I shook it out and reinstalled it. Snorkel definitely made a difference on the amount of dust that made it into the intake system.
Oh, and a prefilter will make it even better.