Nearly a century ago, a tremendous explosion rocked the remote forests of Siberia. To this day, the weird event is considered to be one of the world's greatest unsolved mysteries.

On the morning of June 30, 1908, a massive explosion occurred in the air above the remote, isolated forests near the Stony Tunguska River in Siberia, Russia. For that reason, it is often called the Tunguska event.

The blast was estimated to be between 10 and 20 megatons of TNT -- 1,000 times more powerful than the atomic bombs dropped on Hiroshima and Nagasaki in 1945. The explosion felled an estimated 80 million trees over an area of 830 square miles. The shock wave is estimated to have measured 5.0 on the Richter scale, according to a Web site.

One eyewitness who lived about 40 miles south of the explosion described the sky being "split in two" and fire appearing high and wide over the vast forest.

"At that moment, I became so hot that I couldn't bear it, as if my shirt was on fire; from the northern side, where the fire was, came strong heat," the witness said. "I wanted to tear off my shirt and throw it down, but then the sky shut closed, and a strong thump sounded, and I was thrown a few yards. I lost my senses for a moment, but then my wife ran out and led me to the house.

"After that such noise came, as if rocks were falling or cannons were firing, the earth shook, and when I was on the ground, I pressed my head down, fearing rocks would smash it. When the sky opened up, hot wind raced between the houses, like from cannons, which left traces in the ground like pathways, and it damaged some crops. Later we saw that many windows were shattered, and in the barn a part of the iron lock snapped."

That account is only one of many from the Siberian villagers who were around to experience the enormous blast. Some of them were convinced that the explosion signaled the end of the world and the final judgment. It is fortunate that the explosion happened in a remote, unpopulated area. If it had occurred over a major city, there is no doubt that the city would have been utterly destroyed and millions of people killed.

But how could such an explosion happen 37 years before the invention of the atomic bomb?

Because the Tunguska region was so isolated, the first recorded expedition to the site didn't happen until the 1920s. Russian scientist Leonid Kulik first journeyed to the site in 1921 and spoke to local people who saw and felt the blast. He deduced that the explosion had been caused by a giant meteorite impact. He persuaded the Soviet government to fund an expedition to the Tunguska region.

Kulik's party finally reached the site in 1927. To their surprise, no crater was to be found. Instead, a vast region of downed trees was found stretching about 30 miles across. Later expeditions would further explore the region devastated by the blast. It is interesting to note that no elevated levels of radiation, which are typical of nuclear explosions, have been found at the site.

Today many scientists believe that the Tunguska event was caused by a meteor or comet which blew up just prior to hitting the Earth's surface. It is often used as an example of what could happen if a meteor or comet were to hit the Earth today, especially over a large metropolitan area.

But others are not sure about that explanation. Some believe that the Tunguska event was caused by the explosion of an alien spaceship. In 1998, a TV show on Turner Network Television referred to the Tunguska event as the "Russian Roswell" and claimed that UFO debris has been recovered from the site. In 2004, a group of Russian UFO enthusiasts claimed to have found the wreck of an alien spacecraft at the blast site.

So today, the Tunguska event remains as one of the strangest episodes in history. And we can only pray that something like that doesn't happen over a populated area.

Contact Mike Conley at 652-3313, ext. 3422 or e-mail nconley@mcdowellnews.com