Asteroid, comet or meteorite impacts are nothing less than titanic game-changers. The collision that brought the curtains down on the age of the dinosaurs, for example, created tidal waves of fluidized rock 2.5 times the height of Everest, and it even managed to forge brand new fault lines all through North America as the crust around the crater cracked, like dropping a bowling ball on a frozen lake.
An impact on Mars a few billion years ago looks likely to have caused continent-sized megatsunamis that washed from the northern hemisphere of the Red Planet all the way to the southern one. Clearly, if the impact is powerful enough, incredible things can happen – and a new study suggests a meteorite smashing into what is now Canada set off a series of volcanic eruptions.
“The effect of large impacts on the early Earth could be more serious than previously considered,” coordinating author Balz Kamber, a professor of geology and mineralogy at Trinity College Dublin, said in a statement. “The intense bombardment of the early Earth may have brought up material from the planet’s interior, which shaped the overall structure of the planet.”
This story involves the Sudbury Crater, one of the oldest and best-preserved impact bowls on Earth. Located in Ontario, it’s a 1.85-billion-year-old depression 250 kilometers (160 miles) across, which is far larger than the far more famous Chicxulub crater.
Can you spot the oval-shaped Sudbury Crater? Landsat 7/NASA
Back then, the continents were arranged into a single cohesive one named “Nuna”. This supercontinent eventually found itself on the business end of an impactor from deep space that was about 15 kilometers (9.3 miles) across. The subsequent violence spread debris across an area of 1.6 million square kilometers (620,000 square miles) – about the area of California – at supersonic speeds.
Devastation-wise, it was a lot more destructive than the impact that landed on the heads of the Tyrannosaurs. It’s not surprising, then, that this new study in the Journal of Geophysical Research: Planets concludes that it set off a chain of volcanoes too by compressing their magma chambers to bursting point.
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.