Geologists have long known that the weight of ice sheets in northern Europe and North America depressed the earth's surface. Parts of those regions are still rebounding following the end of the ice age around 10,000 years ago. Thus the saying, "as solid as the earth" is on rather shaky ground.
Now information from Brazil indicates that we don't have to have a mile or so of ice for the earth's surface to flex. Measurements from a global positioning system site adjacent to a river with a depth gauge showed clearly that the ground moved up and down depending on the water's depth, and thus weight. The movement wasn't much, only roughly 2 to 3 inches, but certainly enough to demonstrate that the earth is not rigid.
The Chihuahuan Desert has the Rio Grande traversing its northern region. Lacking the depth of water of rivers in better watered climes, we shouldn't expect the degree of motion seen elsewhere. Nevertheless, stand near the river bank at the beginning of the next irrigation season; you just might feel the earth move.
Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
