Monday, November 30, 2015
A matter of scale
Limestone is made out of tiny seashells. Layers and layers of tiny seashells, laid down over a mind-bogglingly vast span of time by generations of small critters. Then over another mind-bogglingly vast span of time rainwater will get into the cracks and stay there. In the middle of Iowa, about 74 million years ago, a rock from space bumped into the planet Earth and made a big dent, blowing all the limestone away. The crater is buried, but if you drill a well in Manson, Iowa, you get soft water, while the whole rest of the region has hard water.