IMPACTS & EXTINCTIONS A
The purpose of Chapter 3.1 is to summarize the
most significant impacts and extinctions of the past 300 million years.
Not all really big impacts have led to major extinctions. However, all
major extinctions were caused by the initial effects of a really big impact and
its antipodal effects.
In one way or another, really big impacts did
cause all of the major extinctions of the past 300 million years. The major
extinctions prior to the Permian are too obscure to figure out, yet.
The usual rule is that a big impact will create a hotspot at the
antipode that will move in the direction of the directional force imparted by
the impact. A really big impact will not only create a hotspot, but will also
uplift a continent and cause a major extinction.
One exception to the
rule is the impact at Manicouagan 214 MYA. The impact was large enough (barely)
to uplift the Western Antarctica continent. However, this event did not create
a major extinction. It did create a minor extinction, but it did not cause
enough damage to create a major extinction.
Another exception to the
rule is the huge deep ocean impact 132 MYA that uplifted the South American
continent. This impact and its huge lava outflow at Parana and Etendeka caused
the Valanginian Weissert Ocean Anoxic Event, but not an official major
Yet another exception is the Morokwang impact of 145 MYA.
While this impact did coincide with a minor extinction and the end of the
Jurassic Period, it only created the Greater and Lesser Antilles instead of a
Three other smaller large impacts caused antipodal volcanism
and local damage but no serious extinctions or raising up of continents. These
impacts were the Kara impact of 70.3 MYA, the Popigai impact of 35.7 MYA and
the Chesapeake Bay impact of 35.5 MYA.
A summary of all of the large
impacts of the last 300 million years is shown below.
||Big Minor Extinction
||Ocean Impact, the Bedout Crater off Australia?
||Eastern North America
Atlantic Magmatic Provinces (CAMP) - caused by leaky uplift of Eastern North
||Greater & Lesser Antilles
End-Jurassic was a Big Minor Extinction
Valanginian Weissert Ocean Anoxic Event may or may not have been a major
||End of the
||South Sandwich Islands
||End Eocene Epoch