Airburst "Impact" Events

 An article from SciTech Daily relates "Scientists Uncover New Evidence of Ancient Airbursts That Ravaged Earth Without Leaving Craters." It not only goes over additional evidence supporting a Younger Dryas impact event, but other airburst events. The article begins:

    Emerging evidence suggests Earth has endured far more hidden cosmic explosions than once believed.

    Touchdown airbursts, a form of cosmic impact that may occur more often than the crater-producing events known for wiping out the dinosaurs, are still not fully understood. UC Santa Barbara Earth Science Emeritus Professor James Kennett and his colleagues continue to argue that these powerful explosions deserve far more scientific attention.

    “Touchdown events can cause extreme damage through very high temperatures and pressures,” Kennett said. “And yet they don’t necessarily form a crater, or they form ephemeral surface disturbances, but they’re not the classic major craters that come from direct impacts.”

    Four recently released studies from Kennett and his co-authors highlight evidence for multiple airbursts from different periods in Earth’s past. In these events, an incoming object such as a comet detonates above the surface and releases intense heat and shockwaves. The researchers documented new findings from locations ranging from the deep North Atlantic to the remains of an ancient desert community. Their work points to materials that form only under extreme conditions, such as rare comet-derived elements, molten glass, and spherules produced by high-temperature melting of Earth materials, and shocked quartz that contains distinctive fracture patterns.   

It then goes on to describe impact proxies found in Baffin Bay, just west of Greenland, that support the Younger Dryas Impact Hypothesis (YDIH). It is the first time evidence for the YDIH has been found in marine record. Researchers also examined sediment from the Tunguska event as an example of an touchdown event and revisited evidence from Tall el-Hammam, "the site of a major ancient city in the Levant that is thought to have experienced a similar-sized event about 3,600 years ago."

“The interesting thing about Tunguska is that it is the only recorded historical touchdown event,” Kennett said, and indeed, there are documented eyewitness reports of a fireball in the sky, and photographs of flattened trees. However, for all the studies of the fallen trees and the soils at the impact site, there had up until now been little effort in search of cosmic impact proxies. This study is the first comprehensive evidence of airburst/impact proxies at Tunguska.