We know that most of an iceberg is hidden under water. For that matter, the miniature icebergs that cool our drinks clearly show the same thing. The reason why ice floats is that a piece of ice has a greater volume than an equal weight of liquid water. No big deal—it's something we learn in grade school. We may have forgotten, though, that the part of the ice below the water's surface displaces water that weighs the same as the ice cube. As the ice cube melts, it rides higher in the water.
Many things act this way-even solid ground! Softened at depth by
increasingly high temperatures, dense rock will slowly give way to the weight of a
mountain above it until the weight displaced is equal to that of the mountain. As the
upper portions of the mountain are worn away by erosion, reducing its weight, the
mountain slowly rises, like a melting ice cube. Thus our mountains may last much longer
than the time it would take to wear them to ground level if they didn't
float.
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.