Labels:text | font | screenshot | white | black and white OCR: Sand dunes cover around 20% of the world's deserts. The dunes are often called 'seas of sand', an appropriate name because the winds move and shape the sand so that the terrain changes constantly. The largest continuous expanse of sand is the Empty Quarter or Rub Al Khali, part of the Arabian desert covering over 250,000 sq miles. The largest dune areas in North America are west of Yuma, Arizona and at White Sands National Monument in New Mexico
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