What you are looking at is a massive circular feature within Namibia.
It is a truly beautiful geologic oddity so large that its true extent is not easily visible
except from the air.
Known as Brukkaros Mountain, it's spectacular central edifice measures 3.3 kilometers or
2.05 miles wide, and rises 610 meters or 2,000 feet from the level of the surrounding desert.
Zooming out, we can divide this distinctive feature into three parts.
The central crater, the rugged ramparts, and a debris fan containing eroded rocks comprising
material from the former two sections.
While this might look like an impact crater, much like the buried Roter Kamm impact crater
to the southwest, Brukkaros Mountain is not an impact crater.
And, despite being circular, despite what many reports claim, it is also not a volcanic
caldera.
Instead, while this feature is volcanic in origin, it represents one of the planet's
largest tuff rings.
Brukkaros Mountain formed in a climatic eruption of an unimaginably large size which devastated
the surrounding landscape over a wide radius 77 million years ago.
While this in of itself isn't all that unusual in the geologic record, what is unusual revolves
around the type of magma which produced this event.
As, it did not involve magma that was silica aka silicon dioxide as its largest component,
as instead, the relevant magma was instead more than 50% by weight carbonate minerals,
with numerous CO3 ions.
Known as a carbonatite, not only is this type of lava incredibly rare, but it is also absurdly
valuable.
As, due to the geochemistry of this material, carbonatite is one of the only rocks on the
planet which can contain economic concentrations of 16 rare earth elements.
Rare earth elements are not neccessarily rare per say as for example the rare earth element
cerium is slightly more common than copper, but instead rare earth elements are almost
uniformly distributed throughout the planet's crust, in almost every form of rock.
They almost never occur in concentrations higher than background levels, which means
that while there are a lot of these elements, most are locked away in unprofitable source
rocks.
This, however, is not the case for carbonatites, where numerous rare earth elements occur in
concentrations high enough to be potentially mined for a profit, allowing for their widespread
usage in high tech electronics.
And, mining this beautiful structure is likely unecessary to produce what very well could
be many billions of dollars worth of ore.
As, radiating outwards in every direction surrounding Brukkaros Mountain are numerous
raised ridges referred to as dikes that represent now exposed failed magmatic intrusions.
These are presumably more rare earth element enriched than the host rock, yet to the best
of my knowledge, it does not appear that any person or company has performed a thorough
rock analysis on the concentrations of various rare earth elements in these rocks.
Since we do now know what they might contain, I will make an educated guess that these dikes
could contain economic concentrations of the rare earth elements lanthanum, ytterbium,
cerium, and ytrrium as these are found in many similarly aged carbonatites within Namibia.
If you were to go back 77 million years ago, Namibia would have been the site of a north
to south trending rift zone where the crust was slowly spreading apart to the east and
west.
This spreading thinned the crust, causing partial melting to begin of rocks in the lower
crust, creating phonolite magmas.
One such intrusion rose through the crust which contained abundant dissolved potassium
oxide, carbon dioxide, and sodium oxide.
Eventually, this magmatic intrusion stalled, but at the same time, pockets of the phonolite
were getting increasingly enriched in alkali elements and carbon dioxide.
Eventually, this reached a threshold which caused the two different composition liquids
to separate from one another in a manner similar to adding vinegar to oil.
This is how the large body of carbonatite magma formed.
It then rapidly shot upwards, but stopped right below the surface, forming a laccolith.
Expanding over the timespan of what may have only been a few months, it pushed up overlying
rock, causing a 10 kilometer wide section of ground to be pushed upwards by a whopping
400 meters or 1312 feet.
Then, groundwater finally began interacting with the magma, which subsquently flashed
to steam and exploded, causing the uplifted ground to be largely destroyed in a plinian
eruption.
After the eruption ended, what was left behind was a plain of ash that in its center had
a thick ring of material known as a tuff ring.
After tens of millions of years of erosion, the surface level of the top of the crust
decreased, causing carbonatite dikes to become exposed on the surface.
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