), at 11 seconds past 0017 hours Mean Greenwich Time. Edward F.On 30 June 1908, the Tunguska meteorite fell near the Podkamennaya (Stony) Tunguska River in Evenkysky National District (60★5' N. Additional on-site investigations were performed by Soviet scientists in 1958 through 1961 and by an Italian-Russian expedition in 1999. The blast had been initially visible from about 800 km (500 miles) away, and, because the object vaporized, gases were dispersed into the atmosphere, thus causing abnormally bright nighttime skies in Siberia and Europe for some time after the event. At the time, seismographs in western Europe recorded seismic waves from the blast. Eyewitnesses who had observed the event from a distance spoke of a fireball lighting the horizon, followed by trembling ground and hot winds strong enough to throw people down and shake buildings as in an earthquake. The epicentre was easy to pinpoint because the felled trees all pointed away from it at that spot, investigators observed a marshy bog but no crater. Around the epicentre (the location on the ground directly below the explosion), Kulik found felled splintered trees lying radially for some 15–30 km (10–20 miles) everything had been devastated and scorched, and very little was growing two decades after the event. The remote site of the explosion was first investigated from 1927 to 1930 in expeditions led by Soviet scientist Leonid Alekseyevich Kulik. Thus, the Tunguska blast charred the forest but did not produce a sustained fire. The radiant energy from such an explosion would be enough to ignite forests, but the subsequent blast wave would quickly overtake the fires and extinguish them. The only likely remains of the object that have been found are a few small fragments, each less than a millimeter across. Because the object exploded in the atmosphere high above Earth’s surface, it created a fireball and blast wave but no impact crater. Objects of this size are estimated to collide with Earth once every few hundred years on average ( see Earth impact hazard). Other scientists maintain that the event was caused by an asteroid (large meteoroid) perhaps 50–100 metres (150–300 feet) in diameter and having a stony or carbonaceous composition. Such clouds are thought to be the result of a sudden influx of ice crystals into the upper atmosphere (such as those that could have been triggered by the rapid vaporization of a comet). On the basis of historical records of significant noctilucent cloud development in the skies over Europe following the event, some scientists contend that a comet caused the explosion. Learn about the explosion of a possible comet or asteroid over the Siberian taiga See all videos for this article SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.This Time in History In these videos, find out what happened this month (or any month!) in history.#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.
0 Comments
Leave a Reply. |