A drop of water, a grain of sand, a bit of ice--what difference could they possibly make on the landscape? But these underrated agents of change never travel alone. Drop by drop, water dug the Grand Canyon. Sand carried by the wind has sculpted great arches and hoodoos in deserts from Mongolia to Utah. Glaciers that once covered entire continents created fjords in Iceland and the Great Lakes in North America. Given time, erosion will overcome the most powerful forces. And it has all the time in the world. Book jacket.