Rocky Mountain News, Marc Piscotty, file) ** MAGS OUT TV OUT **, Associated Press
FILE - In this April 14, 2003 file photo, the downtown Denver skyline is pictured, with the foothills, and the Rocky Mountains in the background. Geologists say they might finally know why the Mile High City is a mile high: water. A new theory from the University of Colorado suggests that chemical reactions triggered by water far below the Earth’s surface made this part of the continental plate lighter than surrounding areas, causing it to rise, lifting Denver’s location 5,280 feet above sea level.

DENVER — Geologists may finally be able to explain why Denver, the Mile High City, is a mile high: water.

A new theory suggests chemical reactions triggered by water far below the Earth's surface could have made part of the continental plate less dense. Because the plate floats on the Earth's mantle, the lighter portion might have risen like an empty boat next to one with a heavy cargo — lifting the vast High Plains far above sea level.

According the theory from the University of Colorado, this is why present-day Denver ended up 5,280 feet above the sea.

Geologists have long been puzzled by how the High Plains could be so big, so high and so smooth. The region covers thousands of square miles and ranges from 2,000 to 6,000 feet above sea level.