The most remote permanently inhabited island on the planet is also volcanic in origin.
Known as Tristan da Cunha, this island is only accessible via a 6 day boat trip.
The island was the site of a famous volcanic eruption from 1961 to 1962, leading to a temporary
evacuation of the entire island’s population, which was 264 residents.
Although this was the only eruption in historic times, the young appearance of much of the
island suggested that in reality the island is far more active than was first thought.
A recent paper verified these observations, as it confirmed the presence of 4 more recent
volcanic eruptions.
This video will discuss this remote volcano and it’s recently dated new eruptions.
The island of Tristan da Cunha is located in the remote Atlantic Ocean, where it is
1,750 miles or 2,810 kilometers west of Cape Town in South Africa.
This volcanic island is part of a group of three islands which all exist due to an underlying
hotspot in the mantle.
The hotspot is known as the Tristan hotspot Hotspot, and has been active for more than
120 million years.
Remnants of volcanic activity from this hotspot can be found on the coasts of both South America
and Africa, which were once merged.
As the hotspot did not move, the overlying continents spread apart, thus leading to the
creation of two volcanic ridges.
Approximately 3 million years ago, lava from this hotspot erupted onto the ocean floor
at a depth of 3500 meters below sea level.
Over the next 2.5 million years, the volcano frequently erupted, emplacing large amounts
of lava onto the ocean floor.
Approximately 1 cubic kilometer of lava was added to its edifice every 1,000 years.
Eventually, this massive shield volcano broke the ocean surface, erupting in an explosive
manner.
This occurred sometime around 148,000 years ago.
After this occurred, it did not take long for the central volcanic cone to build an
island which was 12 kilometers wide.
This island had a uniform slope unlike its modern appearance which contains relatively
flat sections of land near the coastline.
Numerous highly explosive eruptions occurred at its peak, producing vulcanian style explosive
eruptions which produced pyroclastic flows.
The largely unvegetated summit of the peak contains a 300 meter wide crater and is colored
due to the thick beds of ash present.
More distant sections of the island were built by flank eruptions from both cinder cones,
lava domes, and maar explosion craters.
Cinder cones can be found throughout the island with varying degrees of erosion, which created
long distance lava flows.
The 3 maar craters shown here are known as “the ponds” and formed in explosive phreatic
eruptions.
30,000 years ago, the shape of the island permanently changed as a massive landslide
occurred.
150 cubic kilometers of the island’s edifice slid off to the northwest, traveling more
than 40 kilometers before it stopped.
This created a large gouge on the northwest of the island which is still visible today.
In the aftermath of this eruption, small lava flows began occurring on alluvial fans which
had formed.
These expanded the overall island, one of which is now the site of the island’s main
settlement.
The lava flows this settlement is built on are approximately 7,000 years old.
In terms of recent volcanic activity, the main peak which is 2,062 meters in height
is completely unvegetated and is covered in young looking volcanic ash.
Although this ash has not been dated, it is likely the result of a large eruption in 1750.
With this being said, the majority of recent eruptions have occurred elsewhere on the island
such as the 1700 AD eruption which formed the Stony Hill cinder cone.
Other young eruptions occurred at the patches in 356 AD, and the Hillpiece cinder cone in
774 BC.
The most recent eruption on the island lasted for 5 months from 1961 to 1962 and occurred
on the north section of the island, building a new lava dome out of phonolite.
Overall, no part of this island is truly immune from volcanic activity, as an eruption could
occur anywhere.
Any future eruption on the island will once again require the entire island’s populace
to be evacuated due to threat of lava bombs, ash fall, pyroclastic flows, and lava flows.
The odds of such a future eruption are about 1 in 460 each year.
Using the US Geological Survey method of rating volcanoes, Tristan da Cunha would be classified
as a high threat volcano.
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