On This Day

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Associated Press
A 1953 photo of the damage done to the Siberian forest by the Tunguska Event 45 years earlier.

On This Day: Tunguska Event Flattens 800 Square Miles of Trees in Siberia

June 30, 2011 05:00 AM
by Haley A. Lovett
On June 30, 1908, a bit of space debris entered the Earth’s atmosphere and exploded over the Tunguska River in Siberia, becoming the largest natural explosion in modern history.

Shockwave Felt Thousands of Miles Away

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On the morning of June 30, 1908, residents of the small town of Vanavara, Siberia, felt the scorching heat of a distant explosion in the sky. According to Time magazine, even though Vanavara was 40 miles away from the explosion, items fell from the walls of houses there, and windows were cracked because of the wave of heat.

The Tunguska Event, named so because of its proximity to the Podkamennaya Tunguska River in Siberia, flattened thousands of acres of forest and caused cloud formations over the region that reflected light and made the night sky bright for days, according to NASA. Animals were killed and forests were destroyed, but there was no reported loss of human life, due mainly to the remote location of the explosion.

The cause of the explosion was a piece of space debris—either a meteoroid or a comet—that entered the Earth’s atmosphere and exploded miles above its surface. This piece of space debris is thought to have been more than 100 feet across and traveling at tens of thousands of miles per hour, although estimates of its size and weight vary greatly because no remnants have been recovered.

Encyclopedia Britannica explains that the fireball, created from the explosion of the space debris, could have caught the forest on fire, but was almost immediately put out by the shockwave that flattened the surrounding forest.
 
NASA explains that due to the remote location of the explosion, it was not until 1927 that an expedition led by scientist Leonid Kulik was able to study the Tunguska Event site. The explorers were easily able to locate the center of the damage (and thus the location directly under the explosion) because the trees had been flattened to point away from it.

The damage caused created a similar pattern of destruction to that of the atomic bomb dropped on Hiroshima, Japan, although many sources say that the Tunguska blast was hundreds or even thousands of times as powerful as the man-made atomic bomb.

Theories Sbout the Origin of the Tunguska Event

In 2009, researchers from Cornell released a paper suggesting the Tunguska Event was caused by the impact of a comet. Although scientists have long agreed that the event was caused by the impact of space debris, debates have raged over exactly what type of debris entered the atmosphere in June of 1908.

The Cornell researchers observed that after the launch of the space shuttle Endeavor in 2007, noctilucent clouds (night-visible clouds made of ice particles) formed, similar to those seen after the Tunguska Event. The researchers concluded that the Tunguska Event clouds could only have been formed by a massive amount of melting ice, which could have come from an icy comet.

Another 2009 study suggested that perhaps the Tunguska Event was caused by a bit of space debris “skimming” the Earth’s atmosphere. The scientists behind the study claim that this would explain the lack of debris found on Earth. The scientists also identified a possible candidate for the event: Comet 2005NB56. They think the object was deflected back into orbit around the Sun and that it may come into contact with Earth again.

In 2007 a report co-authored by Giuseppe Longo claimed that Lake Cheko, located five miles from the center of the Tunguska damage, may be the result of the incident. Although research in the mid 1900s suggested that the lake was not a crater formed by the impact of a comet or meteoroid, newer sonar and lakebed sampling technology suggests that perhaps Lake Cheko is the result of the 1908 explosion.

Background: Space Debris

The different kinds of space debris are often confused with each other. Asteroids are objects that originate from the asteroid belt, meteoroids are space objects smaller than 1km across, a meteor is the light and sound made when a meteoroid enters the Earth’s atmosphere, and a meteorite is any bit of meteoroid that falls to the Earth’s surface. For more information about space debris and the study of space debris, visit our feature Space Debris: Asteroids, Comets and Meteoroids.
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