There are many tall mountains around the planet, such as Mount Everest and Denali. However, very
few of these very tall peaks are volcanoes. And of those that are volcanoes, such as Kilimanjaro,
even fewer are still active. As such, the Ojos del Salado volcano in Chile is quite impressive.
It is the tallest volcano on the planet, and stands at 6879 meters above sea level. It last
erupted in 1993, and will certainly erupt again. This video will discuss this fascinating volcano,
and mention what its future hazards are. The Ojos del Salados volcano is located
in eastern Chile where it partially straddles the border with Argentina.
As the tallest point in Chile, Ojos del salado exists due to the subduction of the
Nazca tectonic plate underneath the South American plate off Chile's western coast.
The subducted crust from this collision then melts and migrates upwards until it erupts on
the surface, thus forming a series of volcanoes. Although we aren't exactly sure how old Ojos del
salado is, we do know that the volcano is at least 1.2 million years old due to radiometric dating.
However, before Ojos del salado began forming, a similar looking volcanic edifice stood where the
volcano is today. Then, at some point in the last 5 million years, a supermassive eruption
occurred on the surface. As many cubic kilometers of lava and ash were ejected during this eruption,
much of the underlying magma chamber became empty, creating stress on the overlying
rock. Eventually, this stress became too much and a massive section of rock collapsed downwards,
forming a large 18 by 13 kilometer wide caldera. After this eruption, magma slowly filled the
space which was partially filled by the caldera collapse. As a result, the center of the caldera
was pushed upwards in what is called a resurgent dome. The Ojos del Salado volcano was born here,
when cracks created by this uplift allowed magma to reach the surface.
The initial eruptions at this new volcano built a series of partially overlapping
lava domes. The reason why the eruptions created small domes instead of long flows of lava was
due to the lava's viscosity. The more viscosity lava has, the steeper of an edge a lava flow has,
and the more slowly it moves. In this case, the lava which erupted had the composition of dacite,
which has a very high viscosity. As these eruptions continued,
they became increasing explosive and created a series of 300 meter wide volcanic craters. As
you look around the volcano's lava dome complex, you can see at least a dozen examples of such.
As more and more lava domes were constructed over hundreds of thousands of years,
a northward trending pattern became evident on this volcano. These straight lines likely
represent the result of tectonic stress in the region, due to the uplift of the Andes.
As time progressed, it appears that newer lava domes formed in an eastward direction
compared to prior lava flows. By the end of the last ice age,
Ojos del salado was its modern height, standing at almost 7 kilometers above sea level.
The only confirmed recent eruption from this massive volcanic complex occurred in 750
AD. Although exactly which vents formed during this eruption is unknown, it was cited as creating
a dozen volcanic cones, craters, and lava domes. Then, on November 14th 1993, a small unconfirmed
eruption may have occurred at this volcano. Nearby climbers and workers of a local
border outpost noted a gray column of gas that rose a few kilometers into the sky.
Again, on November 16th, a similar occurrence was witnessed. My interpretation of these events
is that a series of small explosive phreatic eruptions which did not erupt any lava had
just occurred at Ojos del Salado. Since then, no additional activity has been documented.
Due to the remoteness of this volcano, any future eruptions are unlikely to
pose much of a hazard to anyone other than climbers in the region. These climbers,
along with anyone within a 15 kilometer radius at the time of an eruption could be at risk of being
engulfed in a resulting pyroclastic flow. If a large eruption were to occur, it could cause a
significant quantity of overlying snow and ice to melt, thus generating a series of lahars.
These lahars could wash away segments of roads along portions of Route 31 in Chile
and Route 60 in Argentina, potentially up to 60 kilometers from the volcano's summit.
Overall, Ojos del salados is a remarkably tall volcano that has the potential to erupt again,
but likely will stay dormant for some time. I hope that you enjoyed this video. If
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