Lakes Their birth, life, and death

Depending on how they're measured, there are as many as 117 million lakes in the world, according to Smithsonian magazine. Saylor, professor of mechanical engineering at Clemson University, delivers science in a layperson's language to detail their forms, how they're created, how they're miraculously sustained, and, yes, how they die. Revelations abound: 45 percent of the Earth's lake water is found in salt lakes; Lake Vostok, a subterranean body of water beneath Antarctica that's roughly the size of Lake Ontario, hasn't been exposed to the atmosphere in as many as 10 million years; a lake "overturns" once, maybe twice, a year, enough to supply a year's worth of oxygen to its plant and animal life "in one great gulp"; and the surface tension created by the desire of water molecules to stay close together allows some 1,200 different creatures to literally walk on water. Millions of lakes notwithstanding, Saylor warns of the dangers to the world's freshwater supply by human activity, citing, as just one example, the fated Aral Sea. An excellent primer for libraries of any size.