When people think of Australia, volcanoes are typically not the first thing that comes
to mind.
Yet, the country indeed contains several active volcanoes, one of which erupted in 2005.
The volcano in question is not located on the mainland, but rather is a distant island
territory of Australia.
I am referring to McDonald island, which contains the second most active volcano in the country.
Its numerous recent eruptions are only second to the more numerous eruptions from the nearby
Heard Island.
This video will discuss the McDonald Island volcano, and mention what it’s future hazards
are.
The McDonald island volcanic complex can be found just north of mainland Antarctica in
a remote section of the southern ocean.
Specifically, it is 4100 kilometers west southwest of the city of Perth.
Just like the much larger Heard Island to the southeast, the McDonald Islands exist
due to an underlying hotspot in the crust which has been active for over 130 million
years.
This hotspot is called the Kerguelen hotspot and is also responsible for volcanic activity
in the much larger Kerguelen islands.
The McDonald Islands comprise three islands: McDonald Island, Flat Island and Meyer Rock.
These islands each represent distinct volcanic vents and represent emergent peaks of a largely
submarine volcano.
Each of these islands are largely comprised of overlapping lava domes which erupted highly
viscous magma that formed a rounded edifice.
The McDonald island volcano began forming approximately 90,000 years ago, when magma
from the underlying hot spot erupted onto the ocean floor.
Beginning at a depth of approximately 300 meters, a viscous variety of lava called phonolite
began building a submarine volcanic cone.
Over the subsequent thousands of years, this volcano grew in size until it was just below
the ocean surface.
When it erupted again, it did so in an explosive manner, thus forming a plateau out of volcanic
ash called tuff.
A series of subsequent eruptions formed a group of overlapping lava domes, thus causing
the small island group to grow in height and area.
Then, 75,000 years ago, the volcano became dormant.
For the subsequent tens of thousands of years, no activity occurred other than the occasional
steaming fumarole on its summit.
Then, in 1992, after 75,000 years of dormancy, McDonald island produced a new eruption.
However, this unexpected eruption was not immediately noticed.
This eruption was first learned about when a large volume of phonolite lavas washed up
on nearby Heard Island.
These light colored lavas contained small amounts of pumice, indicating an explosive
component to the eruption.
It was later determined that these lavas originated from a hidden submarine vent just offshore
of the McDonald island complex.
Then, in 1996, a vent on McDonald island itself erupted.
This new eruption produced a series of short distance pyroclastic flows and ejected bombs
of lava in a several kilometer radius in what is termed a vulcanian eruption.
Additionally, several large flows of lava occurred, which sent viscous dome forming
lava flows towards the ocean.
Several years later, in 2001, a similar eruption doubled the size of the overall island.
This eruption was significant as it caused the main island to connect to one of the closer
satellite islands called Flat Island.
A smaller eruption occurred in July of 2005, since when no additional eruptions have occurred.
Although it has now been more than a decade since it’s last eruption, the previous long
term period of dormancy at this volcano shows that it has the potential to erupt again.
When the next submarine or explosive eruption occurs, it will pose a potential hazard to
aircraft which fly over this part of the Antarctic.
Small ash particles emitted by explosive eruptions can cause damage to airplane engines, thus
creating the need for an exclusion zone to be created during such an eruption.
Using the US geological survey method of rating volcanoes, the McDonald Island volcanic complex
would be classified as a very low threat volcano (score = 0).
Overall, this beautiful and remote Australian volcano is likely to erupt again in the next
20 years, thus further expanding the island.
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