More than 250 small earthquakes occurred in Yellowstone Park between Dec. 26 and Monday.

Scientists wonder if last month's swarm of tremors, the most numerous and intense in this area in many years, might be a harbinger of a larger event.

Yellowstone National Park sits atop a supervolcano. The entire park is the depression of a caldera more than twice the size of Oahu that is the result of an unimaginably large eruption some 600,000 years ago.

By comparison, the caldera left by the explosion of Mount Saint Helens in 1980 is about the size of downtown Honolulu.

Saint Helens ejected 1.4 billion cubic years of ash that was detectable over an area of 22,000 square miles.

  The last Yellowstone eruption, which was not even the largest in Yellowstone's history, ejected 2,500 times the ash of the Saint Helens explosion.

Should we be alarmed by this uptick in activity?

Scientists studying Yellowstone from the U.S. Geological Survey, University of Utah and National Park Service at the Yellowstone Volcano Observatory say that recurrences of cataclysmic eruptions are not regular or predictable.

A supervolcano eruption at sometime in the future is inevitable with 100 percent probability. Eight supervolcano eruptions are known from the geologic record and there may be even more.

  Although nothing, including the recent earthquake swarm, points conclusively to an imminent eruption, the researchers note that Yellowstone erupts about every 600,000 years.

Geologists continuously monitor the inflation and deflation of the Yellowstone Plateau, which indicates pressure changes in the magma chamber that lies as close as 5 miles below the surface in some places.

The elevation of the caldera is 35 inches higher than when measurement began in 1923, and it has been moving upward since mid-2004 at a rate of up to three inches a year - more than three times faster than has ever been measured previously.

An explosion matching the last Yellowstone eruption, which released 60 million times the energy of the Hiroshima bomb, would most certainly result in millions or even billions of deaths worldwide, both directly and indirectly.

One study predicts that half the U.S. could be covered in ash up to 3 feet deep. Earth could experience a “;volcanic winter”; with ash in the atmosphere keeping sunlight from reaching Earth's surface for several years.

The largest supervolcano eruption within the last 25 million years occurred at Lake Toba in Sumatra 73,000 years ago. The energy released was at least 15 percent greater than Yellowstone and 20,000 times greater than the largest human-made nuclear explosion.

  It plunged the Earth into a volcanic winter, and might have eradicated 60 percent of the human population, leaving as few as a thousand breeding pairs to propagate our species.

We cannot predict, prevent or prepare for such cataclysms, but we must be humbled by the knowledge that such events have been and will continue to be an important part of the history of our planet on geological time scales.

Without them we would most likely not be here at all, and they might someday render us extinct like the dinosaurs.