填空题 Few of us realize how dust storms in the Sahara Desert can affect us directly in this country, but in fact, 1 can be felt many miles away. This has become more apparent in recent years as 2 with which dust storms occur has risen sharply. To understand how this situation 3 , you need to know something about the desert landscape. Under normal circumstances, there is 4 and lichen lying on top of the soft sand. The winds that 5 , although they may be powerful, don"t blow away the sand because the crust 6 . But this protective covering, which has been in place for thousands of years, 7 , especially over the last decade or so. One reason for this is that people who 8 nowadays prefer jeeps to camels, and these vehicles are 9 . Of course, there are other contributing factors as well, the main two being 10 and deforestation on a large scale.
But how is it that these dust storms 11 ? Well, storms in the Sahara send dust 12 , and it can descend many thousands of miles away. If you 13 , you can sometimes see red desert dust on the snow below! And this dust can 14 . It can, for example, carry cattle disease to distant places. In addition, 15 can fall on the sea, preventing the rays of the sun from 16 over large areas. Experts believe that the destruction of coral reefs in the Caribbean, 17 , can be traced back to this effect. Perhaps more worryingly, the dust can even 18 in Greenland. The ice, which is now dark in color, no longer reflects the sun"s rays, so it 19 . So it appears that the increase in dust storms is yet one more of the many factors 20 .