Largest megaripples on Earth discovered

 作者:邢卯六     |      日期:2019-03-08 11:14:03
THEY may look like low dunes, but the cresting ridges pictured above are the world’s largest “megaripples”, a phenomenon that had been thought impossible on our planet. Wind-formed ripples are not the same as dunes because they are shaped by the airflow less than 2 metres above the ground. The key factor for dunes is air fluctuations as high as 4 kilometres up. Most such ripples are no bigger than those created by waves on a beach. Given high winds, light grains and geologic timescales, however, they can grow. Juan Pablo Milana of the National University of San Juan, Argentina,