Wikipedia....Always take it with a grain of salt. I have seen articles there that are quite well done (usually in areas I have had formal training in....archaeology and history of ancient cultures).

That said, Wikipedia should be taken as any research; one voice of many. Research, form an opinion and look for additional arguments that either backs up or contradicts the findings.

That said, with regards to desert forming, remember, the true definition of a desert is an area with either little rainfall or an area that loses more water than it receives. Technically, the Arctic/Antarctic are cold deserts, with the Antarctic desert being the worlds largest, larger even than the Sahara.

Not all deserts look like Arizona/Sahara/Mongolian. For instance, the Okanagan region in British Columbia is a Desert, even with its pine trees, and scrubs because of it's low yearly precipitation.

So, because you are understandably reluctant to accept Wikipedia, the following takes you to the University of California's Paleontology Museum's website with articles on the various biomes of earth:

http://www.ucmp.berkeley.edu/exhibit...es/deserts.php