On June 30, 1908, a meteoroid airburst 6-10 km (4-6 mi) above Earth’s surface over Siberia created a downward atmospheric shockwave in an isolated area near the Tunguska River. The airburst levelled forest in a zone of some 2,150 km2 (830 mi2 ) in a rough width of 70 km (43 mi) and length of 55 km (34 mi). Although observed and photographed in the 1920s, this damage was not better understood until well over 50 years later.

In such an airburst, meteoroid material compresses as it penetrates Earth’s atmosphere until the atmospheric pressure wall causes the material to explode as an airburst that produces downward shock, along with a rain of particles and heated gases.

Over a century later, international scientists from many disciplines have drilled down through physical evidence, site core samples, underwater investigations, and more, trying to solve Tunguska’s riddle. One team has developed models of impact, and even characterized the nature and speed of the meteoroid’s breakup and impact on Tunguska’s landscape. The research is ongoing. You can check out their latest findings – documented with detailed maps and photos. Amazing science with proof yet to come!

30 June 2008: Lake Cheko, a century after the event. [Courtesy – the Tunguska Page of Bologna University: ]

30 June 2008: Lake Cheko, a century after the event.
[Courtesy – the Tunguska Page of Bologna University ]

Today, with several modern technologies in place, it is estimated that airbursts occur in Earth’s atmosphere every year. Additionally, other meteoroid material makes impact of some kind on land in the form of fragment showers or small craters. It is difficult to calculate how many or how often meteoroids have penetrated Earth’s atmosphere to strike the planet’s surface.

From the Tunguska event to other meteor craters large and small on Earth, we have learned that water fill and/or vegetative regrowth can hide evidence of impacts over time. And that evidence is only what we could see on Earth’s landforms! Since 70% of our planet is covered in water, it is difficult to know more about the historical record of either airburst or other impact events. Difficult is not impossible, of course. It becomes another field of science and risk management for future investigation!

B Bondar / Real World Content Advantage

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