What you are looking at is a satellite view of a rather unknown circular feature within
a section of the Saharan Desert in Mauritania.
Despite its appearance, this feature is NOT a maar explosion crater or caldera.
Although there are volcanoes in the Saharan Desert such as Emi Koussi in Chad, Mauritania
does not contain any such active volcanoes.
Rather, this unusual structure is in fact one of the most well preserved impact craters
on the planet, which is called Tenoumer Crater.
It measures 1900 meters wide, and 110 meters deep.
It is the largest confirmed impact crater to form on the planet of the last 50,000 years.
For some additional context, it is 700 meters wider in terms of diameter than the famous
Meteor Crater in Arizona.
So, exactly when did this impact crater form in the Sahara?
How large was the asteroid which formed it?
This video will discuss this well preserved impact crater, and describe the scope of the
impact.
The Tenoumer Crater can be found in the north central section of Mauritania.
Specifically, it is 210 kilometers east of the city of Zouérat.
This large impact crater originated a mere 21,400 years ago, when a medium sized asteroid
was on a collision course with earth.
It measured 100 meters or 328 feet wide, which is just slightly smaller than a soccer or
football field.
This asteroid was termed a chondrite, which formed during the early solar system as dust
and grains of rock merged together to form small asteroids.
As the asteroid made its final approach towards earth, it began to further accelerate due
to the pull of Earth’s gravity.
Entering the upper atmosphere, this mass of rock was traveling at 24 kilometers per second
or 54,000 miles per hour.
Any animals that lived in this section of the Sahara, such as the golden jackal, may
have looked upwards and seen a bright streak of light travelling across the sky.
Due to its high velocity, the asteroid began fracturing into several pieces beginning at
an altitude of 54 kilometers as it quickly burned up in the atmosphere.
Only 3 seconds later, fragments of this asteroid impacted the ground in a 325 meter radius.
These fragments hit the ground with an energy equivalent to the simultaneous explosion of
32 million tons of TNT, thus generating a destructive shockwave.
Mere moments later, a 3000 kilometer per hour wind swept across the landscape, instantly
killing all life in a 6 mile or 10 kilometer radius.
Although there are very few trees in the Sahara, any which did exist in a 20 kilometer radius
of the blast would have been flattened.
Going out a bit further to 30 kilometers away, any plant life would have sustained significant
damage.
Concurrently, this impact generated a magnitude 5.6 earthquake on the Richter scale, which
would have been felt in a 300 kilometer radius.
Due to the immense size of the blast, the associated shockwave from the impact would
have been heard up to 1500 kilometers away.
For some modern day context, with the present borders the shockwave would have been heard
in all of Mauritania, parts of Algeria, Mali, Burkina Faso, Cote d'ivoire, and several other
countries.
After the dust had cleared, the scope of this impact event became clear.
This new crater had a near perfect circular shape owing to its impact angle.
This crater initially measured 1900 meters wide and 400 meters deep.
However, Tenoumer Crater is not nearly as deep as it used to be.
In the more than 20,000 years since this impact, the bottom 290 meters of the crater has been
filled in by sands blown in from winds in the Saharan desert.
If you were to visit this crater, you might find rocks with rounded balls of material
in them that look very similar to chondrites.
However, the vast majority of these are not meteorite fragments, but rather a type of
rock associated with asteroid impacts known as an impactite.
Impactites are formed when asteroid impacts modify underlying rock due to the release
of heat and pressure.
I hope that you enjoyed this video!
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