Water, Water Everywhere - Geography - page 113

What these data tell us is that the vast majority of the Earth's water is unavailable for human
use. In some countries, there are “desalinization” plants that — as the name implies — re-
move the salt from seawater and produce potable fresh water. The process is rather expensive,
however, and helps satisfy the needs of only a few localities — coastal cities, mainly. As a
meaningful solution to the global water crunch, it's simply not feasible given the current level
of technology. And if the amount of potable water isn't worrisome enough, the geography of
supply is often way out of whack with the geography of need. Fresh water is often abundant in
areas where human need for it is scarce. And fresh water is often scarce where human need is
abundant. The following sections show you just how the global water supply is broken down.
Where did all that water come from?
Actually, all that water isn't all that much considering Earth as a whole. Water may cover
70 percent of Earth's surface, but it accounts for only about 0.5 percent of the planet's
weight. Oceans, on average, are about 2 to 3 miles deep, but the average distance from
Earth's surface to its center is 3,960 miles. So the deepest of the deep blue seas is but a
shallow veneer of surface material.
Apparently, all that water was here from the beginning. When Earth was a newborn fire-
ball, its water was mixed together with other planetary matter. Indeed, probably much,
much more water was on the inside of the planet than on the outside. Any substance that
can exist as a solid, liquid, or gas is rather amazing. That's water. Because early-Earth
was so hot everywhere, water was then in a gaseous state instead of liquid. Gases are
lighter than solid matter, so they want to rise. In time, the gaseous water inside the Earth
migrated (rose) to the outside and into the primordial atmosphere. This migration contin-
ued until the crust cooled (blocking the migration of additional internal water vapor to the
surface), although subsequent volcanic activity may be thought of as planetary “burps”
that spew additional water into the atmosphere, along with a lot of other stuff.
Eventually the water vapor in the atmosphere condensed and formed rain. Some scient-
ists believe that downpours began very early on. Others believe that didn't happen until
eons later, after the crust cooled. But most agree that the vast majority of Earth's surface
waters originated in rain that fell from the sky over a very, very long period of time.