The Destructive Power of Water
Many of the features of the Earth's surface have been formed by the cutting and eroding action of moving water. When you think about how hard rock is compared to water, it's easy to believe that it must have taken hundreds of thousands or even millions of years for water to shape the land. This ignorance about how rapidly water cuts rock has cost people their lives.
In April 1987 a 300 foot section of the 540 foot long New York Thruway Bridge collapsed into the Choharie Creek. The moving waters of the creek had created turbulence around the bridge's pilings. Within a few years, this turbulence cut away the rock in which the pilings were anchored, and with nothing to hold it up, the bridge collapsed.
In June 1987 a section of the 2,800 foot long Clearwater Pass Bridge in Florida dropped 10 inches. Divers sent down to inspect the bridge pilings found that more than 10 feet of rock had been scoured away from the bridge's pilings. Similar instances of moving water cutting away solid rock in a short period of time can be found by dams.
When many of these structures were built, it was assumed that it took tens of thousands of years for water to erode solid rock. But experience has now shown us that water is able to do in a few years or even a few hours what scientists once thought took thousands or millions of years. Another lesson to be learned is that we don't need tens of thousands of years to form the water carved features of our Earth!