seas of sand
You know, I hate hiking across sand. Step forward; slide back. Step forward; slide back. The wind picks up grains and drops them in my mouth, in my nose, in my eyes. The hot sun above is reflected from the hot sand below. After half an hour, I am mentally and physically exhausted.
But, wow. Sandy landscapes are some of the most beautiful in the world.
This is a photo from the Taklamakan desert in western China. Geologically, the area is known as the Tarim Basin: the relatively low region between the Kunlun Shan, which mark the northern edge of the Himalayas, and the Tien Shan, the "Heavenly Mountains" that lie between China and Kyrgystan. Geomorphically, the Taklamakan is an "erg" -- a sea of windblown sand, trapped between mountain barriers.
Mars has ergs, too. So does Saturn's moon Titan. There aren't any active ones in the US, though; the Great Sand Dunes of Colorado don't cover enough area, and Nebraska's Sand Hills have been stabilized by vegetation.
But there were ergs in North America in the past. The sculpted sandstones of southern Utah were deposited in one, way back in the Triassic.
And I just learned that, only 33 million years ago, when Earth's climate was changing from hot to glacial, there was a sea of sand that would have buried my house. Or perhaps not; I live on the northern edge of the basin, and maybe the bedrock was exposed here. There isn't much left of the rock that was deposited -- most has been carried away by the various tributaries of the Colorado River as it eroded its way eastward. But once upon a time, the place I live looked something like this:
But, wow. Sandy landscapes are some of the most beautiful in the world.
This is a photo from the Taklamakan desert in western China. Geologically, the area is known as the Tarim Basin: the relatively low region between the Kunlun Shan, which mark the northern edge of the Himalayas, and the Tien Shan, the "Heavenly Mountains" that lie between China and Kyrgystan. Geomorphically, the Taklamakan is an "erg" -- a sea of windblown sand, trapped between mountain barriers.
Mars has ergs, too. So does Saturn's moon Titan. There aren't any active ones in the US, though; the Great Sand Dunes of Colorado don't cover enough area, and Nebraska's Sand Hills have been stabilized by vegetation.
But there were ergs in North America in the past. The sculpted sandstones of southern Utah were deposited in one, way back in the Triassic.
And I just learned that, only 33 million years ago, when Earth's climate was changing from hot to glacial, there was a sea of sand that would have buried my house. Or perhaps not; I live on the northern edge of the basin, and maybe the bedrock was exposed here. There isn't much left of the rock that was deposited -- most has been carried away by the various tributaries of the Colorado River as it eroded its way eastward. But once upon a time, the place I live looked something like this: