DENVER, Colo. - The reservoir site at Snowmass Village, not more than a quarter-mile from the ski slopes, might be viewed as a mass grave for mastodons. In paleontological digging that was underway for 18 fast-paced days a year ago, then resumed for six weeks in spring, scientists and volunteers turned up 41 species, many of them now extinct, including a bison that was half-again as big as bison of today and a ground sloth the size of a grizzly bear.
But the most impressive bones belong to those of mastodons, a now-extinct elephant-like creature that stood 3.4 metres at the shoulder and had teeth adapted for browsing on tree branches. Scientists uncovered bones of at least 30 individual mastodons. But how did the mastodons end up there?
Months ago, scientists began assembling a hypothesis: the mastodons were happily doing whatever they might in the ancient lake when suddenly an earthquake hit. The shaking liquefied the sediments in which the mastodons were standing, trapping them in quicksand from which the beasts were unable to escape.
The process can be seen as similar to the physical process that occurs in a snow avalanche. As snow cascades down a hillside, the friction of even light, fluffy powder produces heat that transmogrifies the snow into an icy concrete-cast that imprisons those within the snow. People buried to their necks have been literally unable to free themselves.
Slowly, according to this hypothesis, the mastodons starved, and once dead their bones disarticulated. More earthquakes further interred the bones deep into the lake sediments - to be found more than 45,000 years later. Scientists are using various dating techniques to get a firm bead on the remains of the mastodon and other specimens. The remains are too old for radiocarbon dating.
How can the scientists prove or disprove their hypothesis? Dr. Kirk Johnson, chief curator at the Denver Museum of Nature and Science, says one test will involve an examination of the tusks of the mastodons. Tusks are somewhat like tree rings, except far more detailed in their record of growth. Like Day-Timers, they can leave also a daily record of growth - and seasons. In winter and spring, they commonly would have darker rings.
So, if all the adult mastodons that died did so in the same season, that might support the earthquake theory. Juveniles presumably would not have survived without food as long.
Whodunnit? Johnson says it may take several years to assess all the evidence collected in the digging. Based on the quality and quantity of mastodon bones, plus the diversity of ages found in species, it's the best mastodon site in the world, he says.