Some Background Details
In 1908, the Siberian region of Tunguska made headline news when an explosion knocked down 80 million trees in an area of only 770 square miles. The mystery was that there was no crater, which led to the assumption that an "air burst" was responsible. The explosion (named the Tunguska Event) was theorized to have happened four to six miles above the actual lands of Tunguska.
Is the idea of a large scale Tunguska air burst realistic? How powerful and how fast would it need to be to cause a mass extinction?