Indonesia’s Samalas volcano may have kickstarted the Little Ice Age

A volcano in Indonesia may be the location of a massive “mystery eruption” that has perplexed volcanologists for decades, according to a new study. The eruption occurred in 1257, and it could also be one of the volcanoes that started a 600-year cold period called the Little Ice Age.

Volcanic eruptions release sulfur into the atmosphere, which eventually falls back on Earth and gets deposited on ice sheets. These sulfur samples can be identified in ice cores obtained from polar regions. From the records, Clive Oppenheimer, a volcanologist at the University of Cambridge, found that an eruption in 1257 may may have been the largest release of sulfur in the past 7,000 years.

But where did the eruption happen? “Not being able to find the volcano can be discomforting,” said Thomas Crowley, a geoscientist at the University of Edinburgh. “If the sulfur wasn’t released by a volcano, it means something very strange is going on that we don’t know about.”

But locating the volcanic source can be tricky. For the 1257 eruption, there were many candidates: Okataina in New Zealand, El Chichón in Mexico, Quilotoa in Ecuador and Samalas in Indonesia (next to Mount Rinjani).

To narrow down their choice, Franck Lavigne at the Pantheon-Sorbonne University and his colleagues had to consider many types of data, just published in the Proceedings of the National Academy of Sciences. “They do a great job of combining historical data, geochemistry evidence, carbon dating, and physical data to arrive at the conclusion,” said Erik Klemetti, a geoscientist at Denison University and author of the popular Eruptions blog. “Their case for it to be Samalas is compelling.”

The historical data comes from Babad Lombok, which are records written down on palm leaves in Old Javanese. They describe a horseshoe-shaped collapse, which can occur when empty space is created under a mountain on ejection of large amount of magma.

Carbon dating is a commonly used technique, but its estimates are not accurate enough. Lavigne had to rely on comparing geochemical fingerprints, which gives a unique ratio of chemicals present in the ash from every volcano. The two sets of these geochemical fingerprints come from volcanic ash in ice core samples and the possible site of a volcano.

“In this study, the error margins for the chemical analysis are quite large,” said Rebecca Williams, a volcanologist at the University of Hull. “But I appreciate that matching the ice core data with volcanic samples is very difficult.” This is because the ice core samples often yield only one or two grains of the ash, which need to be subjected to many tests.

Volcanic eruptions, especially those containing a lot of sulfur, can have a large impact on the climate, which then have social, economic and environmental knock-on effects. An 1815 eruption in Tambora, Indonesia is infamous for producing the “year without summer”, one of the chilliest summers in Europe’s history, which was followed by mass shortage of food.

Lavigne speculates that the Samalas volcano could have similar impacts. One such speculation is about the thousands of bodies recovered from Spitalfields in London. Many of these were found to have been shoved in a single grave, indicating some sort of crisis. According to Lavigne, they’ve been recently dated to 1258, only one year after the Samalas eruption.

The Babad Lombok also notes that the volcanic eruption destroyed Pamatan, then capital of the Lombok kingdom. “There is a good possibility that an ancient city lies beneath the ash and pumice deposits of the Samalas volcano,” said Oppenheimer, also a co-author of the study. “Ruins under such deposits are not so uncommon,” added Williams, but finding a whole city might be.

More important, though, could be Samalas volcano’s role in triggering the Little Ice Age. In a 2012 study in the journal Geophysical Research Letters, scientists used climate models to show that a series of eruptions may have triggered the onset of the Little Ice Age. Although the precise timing varies somewhat, this period is typically considered to have occurred between 1250 and 1850.

“A single eruption could not have caused such long-term climate change,” said Klemetti. “Instead, it had to be a sequence of large eruptions, one of which might be the Samalas volcano.”The Conversation

First published on The Conversation.

Image credit: asgeirkroyer

Submerged continent found

A group of scientists from Norway, Germany, South Africa and the U. K. have discovered a submerged continent in the Indian Ocean.

Their measurements predict that the continent, which they have named Mauritia, lies under Mauritius and its broken chunks today extend more than 1000 km northwards till Seychelles.

The discovery was sparked when they found crystals called zircons on Mauritian beaches. Zircons are resistant to erosion or chemical change and some of the ones they found were almost two billion years old, much older than any of the regular soil or sand samples found on nearby islands. Such old crystals, they thought, could only belong to a submerged continent, and may have perhaps been pushed up on the surface by underwater volcanoes.

To confirm whether these zircons indeed belonged to such a continent, they consulted satellite data which can help detect submerged land masses.

Nick Kusznir, professor of geophysics at the University of Liverpool in the U. K. and co-author of the paper that appeared this week in the journal Nature Geoscience, says: “We found that under Mauritius there were areas with an unusually thick Earth’s crust.”

In deep oceans the thickness of Earth’s crust, which forms the upper layer of the planet and protects us from the extremely hot magma underneath it, is about seven km.

But underneath Mauritius and leading to Seychelles, which is more than 1,000 km away, there were large chunks of the crust that were as thick as 30 km. “While we cannot be certain about the origins of the zircons, when combined with the evidence of thicker crusts in such big parts of the ocean floor, we can be quite certain that a small continent existed underneath Mauritius,” says Kusznir. There are a number of popular myths about submerged continents.

For instance, in the 19th century Lemuria, a large submerged continent in the Indian Ocean, was considered to extend from Antarctica to Kanyakumari. But its claimed existence did not stand the test of science. The Earth’s crust consists of seven or eight major “plates”, which are slowly but constantly moving relative to each other.

Over millions of years these have shaped how the world looks today. Some 140 million years ago, the Indian subcontinent split from a supercontinent called Gondwana, which also consisted of modern Africa, Australia, Antarctica and South America.

It eventually collided with the Eurasian plate some 50 million years ago, raising the Himalayas in the process.

Scientists predict that it was in between leaving Gondwana and colliding with the Eurasian plate that this continent Mauritia may have existed as an archipelago, a cluster of islands, squeezed in between Madagascar and the Indian subcontinent.

On the uses of finding such a submerged continent Kusznir says: “A better understanding of the sea floor and such submerged land masses can help us in better exploration of oil and gas in the oceans.”

First published in The Hindu.

Reference: Torsvik et al. Nature Geoscience 2013 http://dx.doi.org/10.1038/ngeo1736
Image from here.

TLDR: Submerged continent found in the Indian ocean

The island M stands for Mauritius

Scientists have discovered a submerged continent in the Indian ocean, between Madagascar and India. According to sediments found on the coast of Mauritius, at some point during the last 2 billion and 600 million years ago, there was an archipelago that separated from Madagascar and the Indian sub-continent. They then got submerged during the tectonic plate movements that resulted in the way land masses exist today.

Reference:  Torsvik, T. H. et al. Nature Geosci. 2013, 223. http://dx.doi.org/10.1038/NGEO1736

Further reading: Sid Perkins in Nature News

Image credit: Nature Geoscience (Supplementary information)

Update: A reader pointed out that perhaps this was the origin of the legends of Lemuria. Although that is not accurate, the Wikipedia article on Lemuria is worth a read.