The Longest Erupting Supervolcano ? 

--- Kerguelen!

I have been facinated by Kerguelen since reading "Desolation Island" by Patrick O'Brian - the fifth book in his Aubrey - Maturin series. Desolation Island is, of course, Kerguelen.

Another reason to find the place interesting is THIS ARTICLE which tells us that the Kerguelen Plateau was a Large Igneous Province (LIP) which erupted for over 30 million years. Most LIPs last less than 5 million.

Eruption started at 122 million and lasted until 90 million. From about 100 million to 20 million years ago it was above sea level, with trees growing. These have been recovered in recent deep sea drilling.

The plateau has since subsided with only Kerguelen and Heard and McDonald islands poking above the waves. Most is at depths of 1,000 to 2,000 metres. The surrounding oceans are at 4,000m.

The article gives a lot of the details and is an easy read - well worth looking at.

The thought of huge islands (half the size of Australia) disappearing gives one food for thought!

Location of the Kerguelen Plateau in the Indian Ocean. NATIONAL GEOPHYSICAL DATA CENTER