What you are looking at is a satellite view of a rather unknown circular feature within
a section of the Saharan Desert in Algeria.
You might think that this feature is just another volcanic explosion crater much like
this maar found in the Manzaz Volcanic Field.
However, this feature is not a volcanic explosion crater but rather a young impact crater.
Known as Amguid Crater, it is one of the best preserved craters on the African continent
which formed within the last 100,000 years.
So, exactly when did this impact crater form?
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 Amguid Impact Crater can be found in the south central section of Algeria.
Specifically, it is 225 kilometers southeast of the city of In Salah.
Before I state how old this impact crater is, I must note that very few fragments of
the meteorite which formed it have been recovered.
Thus, age dating this crater is limited to a guess based on the level of erosion present.
Official sources state that this impact crater is younger than 100,000 years old, and I agree.
With my knowledge of erosional features, I'd place the age of Amguid Crater at approximately
80,000 years old.
Regardless of its true age, it formed when a small asteroid collided with Earth several
tens of thousands of years ago.
This asteroid measured approximately 50 meters or 164 feet wide, and was a type of space
rock known as a carbonaceous chondrite.
Regular chondrites consist of numerous small spherules of rock compressed together by finer
particles of material.
Carbonaceous chondrites are a subtype of this group as they contain abundant carbon compounds
and sometimes include amino acids.
Thus, this class of meteorites are thought to be partially responsible for the origin
of life on Earth by providing some of the necessary building blocks.
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 13 kilometers per second
or 29,000 miles per hour.
Although this sounds incredibly fast, it is actually quite slow for an asteroid.
I want to note that if this asteroid had been traveling a mere 20% faster, it would have
been completely vaporized and exploded into numerous pieces in the atmosphere.
However, since it was travelling at a slower speed, only a section of material broke off
during atmospheric entry.
When these pieces impacted a patch of ground measuring 200 by 200 meters wide, they generated
a massive explosion equivalent in energy to the detonation of 240 kilotons of tnt.
This ejected large pieces of bedrock, flinging them several thousand feet into the air.
As a shockwave was generated, the site of the initial impact faced a 2000 kilometer
per hour gust of wind.
Expanding outwards from the center, the wind speeds slowly decreased.
At 5 kilometers away, a 100 kilometer per hour shockwave would be felt.
At 10 kilometers distant, its intensity was only 37 kilometers per hour.
Although this city clearly didn't exist at the time of this impact, if you were to be
in the approximate site of In Salah today, you would experience a light shockwave along
with a loud boom which would rock across the mountains of the landscape at a volume of
44 decibels.
As the dust cleared, the new impact crater became visible.
It measured 525 meters wide and 120 meters deep.
Since the impacting asteroid broke into several pieces before it hit, the crater formed was
not a perfect circle.
The fragments of this asteroid are few and far between, as the vast majority of material
was vaporized on impact due to its structural instability.
Since the formation of Amguid Crater, the bottom 55 meters have been filled in my sands
blown in from the Saharan desert.
This fascinating crater is not the only impact crater within Algeria.
To the northeast is the circular Tin Bider crater which contains numerous rings of hardened
rock.
I hope that you enjoyed this video!
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