On 5 separate occasions in Earth's geologic history in the last 500 million years, wide
ranging catastrophes struck the planet, causing the rapid extinction of more than 75% of the
planet's species in devastating mass extinction events.
The most famous of these instances involved the extinction of the non avian dinosaurs
in the Cretaceous Paleogene mass extinction event 66 million years ago.
This extinction was caused due to the effects and release of energy due to the impact of
a 19 kilometer or 11.8 wide asteroid striking the planet off what is now the Yucatan peninsula
of Mexico, which left behind a 180 kilometer wide impact crater which may have initially
been 30 kilometers deep at its center, punching a giant hole through the Earth's crust.
Thus, it has been widely explored if other large impact events caused one or more of
the other "big 5" mass extinction events, but no evidence was found of large craters
linked to the other extinction events.
Instead, the other four mass extinctions are linked with rare massive igneous provinces
termed flood basalts which generally only form on Earth about once every 15 million
years where in a short geologic timespan, hundreds of thousands to millions of cubic
kilometers of lava are erupted over a wide area, releasing enough carbon dioxide into
the atmosphere to stifle life on the planet and potentially cause a mass extinction.
Thus, it seems like 4 of the "big 5" mass extinctions were caused by flood basalts,
including the most devastating of these events, the so called Great Dying when 90% of the
planet's life was wiped out in a geologic instant and the oceans turned acidic.
All of this occurred due to one of Earth's largest known flood basalts, the Siberian
Traps, where in a several hundred thousand year period, this vast area outlined on screen
was coated in a flood of lava and ash which was an average of 2,000 feet thick.
Most flood basalts are associated with the head of a mantle plume reaching the surface,
but we have been unable to identify the hotspot which caused the Siberian Traps.
Due to an increasing amount of evidence which is still highly controversial, I would like
to propose another cause of this flood basalt.
Approximately 252 million years ago a spot which is now far south of Australia on the
Antarctic continent was on the exact opposite side of the planet as where the Siberian Traps
began.
And, although we do not know the age of this feature, it appears that a 480 kilometer or
298 mile wide impact crater exists here, albeit buried by perhaps more than a kilometer of
ice, being known as the Wilkes Land Crater.
Evidence that this structure exists can be found through the depth of regional bedrock
if all of the ice and water was removed, along with a gravity anomaly centered in the middle
of this suspected crater.
And third, a double peaked iridium anomaly being associated with the Permian Triassic
extinction event.
Iridium is an incredibly rare in the Earth's crust as much of what existed during the formation
of the planet now exists in Earth's core.
This is because during the formation of the planet, due to planetary differentiation heavier
elements largely sunk into Earth's core while lighter elements generally ended up in the
planet's crust.
Planetary differentiation only occurs with objects in the solar system that have a certain
mass and density, often with a diameter in the range of more than 100 kilometers.
Thus, anything smaller has not undergone this process and as a result has an abundance of
platinum and other platinum group elements much higher than in Earth's crust.
As a result, when elevated levels of platinum are found in a sedimentary layer rather than
an igneous layer it suggests that an impact event occurred.
However, these two iridium enriched layers have a possibility of instead being from the
Siberian Traps volcanism and not an asteroid impact.
But, did the Wilkes Land Crater, which could be anywhere from 100 to 500 million years
in age cause the formation of the Siberian Traps?
We do not know but it is strangely plausible, and here is why.
About 3.9 billion years ago, a large asteroid impacted Mercury, forming a 1,600 kilometer
wide impact crater.
What makes this impact of particular note is that on the exact opposite of the planet,
called an antipode, the area experienced a sudden and dramatic uplift along with associated
large scale volcanic activity.
Thus, it could be theorized, that a very large impact event can cause volcanic activity on
the opposite side of the planet.
Whenever this ancient impact event occurred, if it does truly exist, it likely involved
a 50 kilometer wide asteroid moving at a speed of 17 kilometer per second, which generated
an explosion equivalent in energy to the detonation of 7.82 billion megatons of TNT, initially
forming an 83 kilometer or 52 mile deep crater which was quickly infilled to be only 1.9
kilometers deep.
This caused a planet wide earthquake which was felt everywhere, and with the blast wave
either flattening or at further distances damaging via ripping off occasional limbs
all vegetation on the planet.
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