It’s been known for a while that the impact crater contains a strange layer of rapidly melted rock, and researchers have suspected that it was all created by the high-energy impact itself. However, a team from Trinity College Dublin have had another look at the textures of the once-molten rocks, and they think they’ve spotted tell-tale features named vesicles, which used to contain volcanic gases.
After checking out samples all over the site, it appears that the volcanic layer in the crater is at least a kilometer (0.62 miles) thick from top to bottom.
The volcanic deposit seems to have formed just after the impact took place, and its composition changed over time. That means the impact into Nuna did indeed melt the crust, but the impact-driven compression – and no doubt fragmentation of the crust – allowed more deep-seated magma to erupt quite prolifically out at the surface.
The eruption was also far from calm. Thanks to seawater flooding the impact crater shortly after it formed, a far more explosive event known as a phreatomagmatic eruption took place.
These types of eruptions are explosive over long periods of time. Juancat/Shutterstock
The scorching lava mixed turbulently with the frigid water, and trapped gas bubbles formed and expanded explosively. The huge temperature different between the two mediums also created gigantic steam blasts, sending lava bombs miles into the air – some of which, incidentally, were identified by the team at the site.
The hypothesis that large enough impacts can trigger volcanic eruptions has been touted before, but it’s been difficult to find any direct evidence for it. This new study, however, is one of the most compelling to date.
There is an important caveat, though. “1.85 billion years ago, the Earth produced 50 percent more radioactive heat than at the time of Chicxulub,” Kamber told IFLScience.
“What this means is that on the early Earth, the crust was at a much higher temperature and could therefore more easily be melted at depth.” So if a sizeable impactor hit Earth today, the same long-lived eruption may not occur. To be fair, though, the catastrophic asteroid impact would be problematic enough.