Approximately 251.9 million years ago, Earth experienced a truly devastating cataclysm.
This cataclysm caused the planet's worst recorded mass extinction event, resulting in the loss
of 96% of all marine species and 70% of terrestrial species.
Known as the Permian-Triassic extinction event, it was caused by the voluminous eruptions
of the Siberian Traps flood basalts.
During a brief time period, numerous fissures and shield volcanoes ejected 4 million cubic
kilometers of lava onto the surface, burying an area the size of Australia in up to 3,500
meters or 11,500 feet of material.
All of this volcanism ejected large amounts of carbon dioxide into the atmosphere, increasing
its concentration from 500 to 8000 parts per million.
This caused large sections of the world's oceans to become acidic and then completely
void of oxygen, killing numerous species.
However, there is something peculiar about this specific flood basalt, which was one
of the planet's largest to ever erupt.
Although tectonic plates have moved since the flood basalts formed, an unusual feature
can be found at the direct opposite side of the planet, referred to as an antipode.
There in Antarctica, a probable 480 kilometer wide impact structure exists beneath the ice.
Although this suspected impact crater has not been dated, its placement indicates that
it may have somehow led to the formation of the Siberian traps, although this is a controversial
hypothesis.
We have known for decades that massive impact events can trigger volcanic activity on the
opposite side of the planet.
For example, 3.9 billion years ago a large asteroid impacted Mercury, forming a 1,600
kilometer wide impact crater.
On the antipode of this impact basin, a very large area experienced a rapid and dramatic
uplift associated with large scale volcanic activity.
Although the exact mechanism why this occurs is unclear, it appears that certain large
asteroid or comet impacts seemingly trigger the formation of a hotspot or trigger volcanic
activity at the closest hotspot on the opposite side of the planet.
Another apparent coincidence exists with the massive Chicxulub impact crater on the Yucatan
peninsula, which formed 66 million years ago and caused the mass extinction of the non
avian dinosaurs.
This crater isn't strictly antipodal to a flood basalt which just happened to be in
ancient India, but it seemingly caused increased volcanic activity along with a change in composition
at the highly active Deccan Traps.
Within 100,000 years of this impact, the Deccan Traps produced an intensive flare up, covering
more than 400,000 square kilometers in molten rock.
One possibility as to why this occurred relates to a known link between large earthquakes
and volcanic eruptions.
While the vast majority of volcanic eruptions are not linked to earthquakes, there is a
definite increase in volcanic activity within 800 kilometers of a magnitude 8 or larger
earthquake for the next 5 years.
Taking this into account, the Chicxulub impact resulted in the equivalent of a magnitude
9 earthquake reaching everywhere on the planet.
This earthquake reignited the Deccan Traps, which already had a large volume of underlying
material, while also causing volcanic eruptions at submarine volcanoes, mid ocean ridges,
and stratovolcanoes around the globe.
One possible direct reason of earthquakes triggering volcanic eruptions is if a large
fault plane moves, it can cause magma to mix.
This is what caused the 1875 plinian eruption of Askja in Iceland, where basalt mixed with
a large rhyolite magma chamber.
While the asteroid was the direct cause of the end cretaceous extinction event, volcanism
associated with the impact also played a role in the overall extinction.
If this theory holds true, it is quite likely that some other large hotspots around the
planet along with their associated flood basalt provinces may have formed due to impact events
from several kilometer wide asteroids or comets.
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