Réunion Island

There’s a little piece of France in the Indian Ocean, east of Madagascar, and it’s frequently on fire.

Réunion Island is the beautiful, inhabited tip of an almost 23,000-foot-tall shield volcano that rises from the seafloor. It has two peaks – Piton des Neiges (Snow Peak, inactive) and Piton de la Fournaise (Furnace Peak) – and a complicated history.

Piton de la Fournaise:

The Réunion Story

Geologists say that somewhere between 5 and 8 million years ago, two adjacent volcanoes began erupting here. One of them was Piton des Neiges, the other has been named Alizés.

It was a powerful but messy business. The volcanic edifice Neiges and Alizés built would grow with each eruption until its flanks grew unstable. Then parts of it would collapse, and the building process would go on.

About 530,000 years ago, the scientists say, Piton de la Fournaise first appeared and Alizés volcano shut down. Neiges and Fournaise carried on until some 12,000 years ago, when Neiges went quiet. It hasn’t erupted since.

However, Piton de la Fournaise, though it collapsed once, is one of the most active volcanoes in the world.

In 2007, for example, it put on quite a show!

The video is in French, but a picture is worth a thousand words.

Reminds you of Hawaii, doesn’t it? That’s not a coincidence.

Réunion Island exists over a hot spot, just like Hawaii. While detailed chemical analysis would show differences, the lava here is generally the same sort of “runny” (basaltic) lava that built the Hawaiian Islands.

Plate motions are different, so there’s no island chain, but Réunion is famous among geologists for possibly being the answer to a big question in plate tectonics.

The scientific expression of the question is complicated, but again, a picture is worth a thousand words.

See how big Asia is compared to India?  This is the geological equivalent of an insect hitting the windshield and totaling your semi while remaining unscathed itself.

See how big Asia (C) is compared to India (B)? This is the geological equivalent of an insect hitting the windshield and totaling your semi while remaining unscathed itself. Réunion Island (A) may be the key to explaining how this is happening.

Basically, Asia is the largest continent on Earth, yet what should just be a little (and self-destructive) slap from a moving Indian subcontinent is raising the Himalayas and Tibetan Plateau and may even be splitting the huge continent apart at Lake Baikal (though the jury’s still out on that).

Seriously, look at the collision in a NASA Earth Observatory animation of events that happened 60-some million years ago: Butter, meet hot knife.

I don’t begin to understand it at all, but apparently the Réunion hotspot could be a mantle plume that formed the Deccan Traps – a huge outpouring of basaltic lava in what’s now India – 60-some million years ago. Some experts suggest, that combined with the global aftereffects of a meteorite asteroid impact near modern-day Mexico, the environmental impact of that large igneous province eruption caused the Cretaceous extinction event, wiping out, among others, the non-avian dinosaurs.

But wait, there’s more.

Now scientists are starting to think the Réunion plume, if it exists, may also be connected with that very unusual India-Asian collision (more information here), which apparently began at about the same time as the Deccan Trap eruption.

If that turns out to be true, it will revolutionize plate tectonic theory.

No one knows for sure yet, but Réunion Island and Piton de la Fournaise Volcano aren’t just beautiful – they may have played a big role in the history of life on Earth.

Categories: Sunday morning volcano, volcanoes

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