A series of minor tremors registered in the Yellowstone National Park has scientists worried and pondering on the possibility of a large-scale earthquake. It's not uncommon for small-intensity tremors to come in the prelude of a large shake, and seismic experts are all the more worried – thus far, the machines have picked up more than 250 of these small shakes. Furthermore, most of these struck the park on Monday alone, which led them to believe that there had to be a large build-up of energy in the crust somewhere beneath the park.

University of Utah professor of geophysics Robert Smith says that the unusual amount of minor tremors, although not completely surprising for those who have had connection to Yellowstone in the past, are very troublesome now, because of their sheer numbers, and the fact that they were clustered in just three days. Normally, it takes more than a week for half this number of tremors to happen, on a regular basis. "They're certainly not normal. We haven't had earthquakes in this energy or extent in many years," the scientist says.

"This is an active volcanic and tectonic area, and these are the kinds of things we have to pay attention to. We might be seeing something precursory. Could it develop into a bigger fault or something related to hydrothermal activity? We don't know. That's what we're there to do, to monitor it for public safety," adds Smith, cautioning others that a large earthquake could cause significant damage in the park, and even result in loss of human lives, if tourists are caught off-guard, and trapped under avalanches or rock and mud slides.

The Yellowstone National Park is simply the caldera of an old volcano that last erupted more than 70,000 years ago. Although that was a long time ago, the geysers that the park is famous for are living proof of the fact that there is still an active layer of magma somewhere 5 to 10 miles beneath the surface. Most likely, the area will still remain active for thousands of years, unless the pressure is not released through another eruption. Thus far, the largest recorded tremor in the three days was 3.3 magnitude on the Richter scale.