Within Ecuador is the world's highest active volcano.
There, the glacier covered Chimborazo volcano towers to 6,263 meters or 20,548 feet above
sea level.
Yet, this volcano is 2,000 feet shorter than the Ojos del Salado volcano in Chile and Argentina,
so why did I say it was the highest active volcano?
The reason is that Chimborazo is considered to be the highest volcano on the planet if
we are measuring from the planet's center since it is located not far from the planet's
equator.
Planetary bodies such as the earth tend to have a bulge due to the force of the rotating
object at their equator which in the case of Earth means the equator is a little more
than 13 miles further from the planet's center than compared to the North or South Poles.
With this being said, although Chimborazo has not produced an eruption since Europeans
colonized the region, recent evidence has suggested that the volcano is still quite
active.
Between 1,000 and 8,000 years ago, Chimborazo erupted on 7 separate occasions, one of which
sent pyroclastic flows more than 7.5 kilometers from its summit.
However, the most notable feature of this volcano other than its height is the fact
that more than 100,000 people including everyone in the city of Riobama live on top of a massive
landslide deposit from this volcano.
The landslide in question occurred approximately 65,000 years ago, when the southeastern slope
of the volcano partially collapsed, causing material to travel up to 35 kilometers away,
covering a grand total of 260 square kilometers.
This landslide is surprisingly easy to spot as it forms a large margin which is several
hundred meters higher than the surrounding landscape.
The Chimborazo volcano is located in central Ecuador where it is 150 kilometers south-southwest
of the city of Quito.
This volcano exists due to an offshore plate collision.
There, the Nazca plate is subducting underneath the North Andes Plate.
The melted material from this collision then migrates upwards, until it erupts onto the
surface, forming a chain of volcanoes.
Chimborazo began forming 120,000 years ago when a volume of basaltic andesite and andesite
lava erupted onto the surface.
As powerful vulcanian explosions occurred, large amounts of ash were scattered over the
surrounding landscape.
Then, a large lobe of blocky lava descended down the local hillside.
After this process repeated hundreds of times, a large volcanic cone had been constructed.
Eventually, eruptive activity changed, constructing a series of large overlapping lava domes,
likely due to an increase in silica content and viscosity of erupted lavas.
Looking at the modern volcano, you can see the elevation where this phase of activity
began due to an overall change in color of the lava flows.
The aforementioned debris avalanche occurred around this change, creating a southeastward
facing horseshoe shaped collapse scar on the volcano.
Not long after, a large explosive eruption occurred, depositing more than 10 meters thick
of ash in a single eruptive sequence.
The next phase of eruptive activity constructed several closely spaced secondary peaks out
of more viscous lavas which had a significant component of dacite.
During the last several glacial periods, glacial advance and retreat carved away at large sections
of the volcano, giving it a highly eroded appearance.
In the last 10,000 years at least 7 eruptions occurred, and although their overall sizes
are not known it could be speculated that each eruption was in the VEI 2 to VEI 4 range.
These eruptions were very explosive, producing pyroclastic flows and large lahars from the
rapidly melting glaciers.
The last such eruption occurred around 500 CE.
If this volcano was to erupt again, hundreds of thousands of people would be placed at
risk.
While thousands could be reached by pyroclastic flows generated by eruption column collapse
or dome collapse, the main threat would be lahars.
Just like Nevado del Ruiz, an eruption could rapidly melt large sections of the glacier,
causing a 100 meter wall of debris to be sent down the volcano's slopes, largely via a series
of already present river channels.
Although Chimborazo is not as active as other volcanoes in the country such as the nearby
Tungurahua, it is still quite potentially dangerous.
Thanks for watching!
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