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

October 10, 2013January 25, 2014 Akshat RathiLeave a comment

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.”

First published on The Conversation.

Image credit: asgeirkroyer

2013 Chemistry Nobel

October 9, 2013January 25, 2014 Akshat RathiLeave a comment

In a rare double, another Nobel Prize has gone to scientists who build models. The 2013 Nobel Prize in Chemistry was awarded to Martin Karplus, Michael Levitt and Arieh Warshel for their work that enables modelling complex chemical reactions on computers.

Scientists build models to understand the world. Those models that survive experiments get widely used. The 2013 Physics Nobel Prize recognised one such feat, where the Higgs boson helped prove that the best-known Standard Model works. Many physicists will be quick to point out that Peter Higgs and François Englert did this by using merely a paper and pen.

To develop their theories, physicists can treat subatomic particles in isolation and then generalise their calculations. Developments in quantum mechanics, the science of the microscopic, mean the behaviour of these particles is quite well-understood. Chemists, however, have to deal with the messiness of the real world, where the number of atoms and the particles within them is large. That is why they rely on computers to do their calculations.

Chemical reactions involve the movement of electrons as atoms interact. Applying quantum mechanics to the reactions of small molecules (containing a handful of atoms) is possible using current computational power. Researchers who developed methods to do that received a Nobel Prize in 1998. But if the molecules that need to be modelled become larger, like proteins which contain thousands of atoms, even current computational power is not up to the task.

This year’s prize went to researchers for making that process easier. They developed methods to deal with the growing complexity of reactions of bigger molecules. They achieved this by marrying two different methods of understanding molecules: quantum mechanics (QM) and molecular mechanics (MM).

MM is based on the classical physics developed by Isaac Newton. It works to explain how large molecules behave (bend, move, vibrate or rotate). In the 1970s, at the Weizmann Institute of Science in Israel, Warshel and Levitt had worked to develop computer programs to use classical physics to model these big molecules.

Then, on completing his PhD, Warshel started working with Karplus at Harvard University. So far Karplus had been dealing with small molecules using QM, but with Warshel he started developing programs to combine the two methods.

They found that a hybrid method improved accuracy without stretching computational power to its limits. Dominic Tildesley, president-elect of the Royal Society of Chemistry, explained: “Computer experiments now combine the quantum mechanics of making and breaking bonds with the classical mechanics of the movement of proteins. Their programs modelled the active parts of a molecule (where the reaction took place) more accurately using QM and the rest with MM. This marriage led to what is commonly known as the QM/MM approach.

“Today QM/MM is very widely used,” Jeremy Harvey at the University of Bristol, said. “Chemists, biochemists, geochemists and chemical engineers all use it.” Its application has helped develop better drugs, improve environmental models and understand the oceans. Since the 1980s, incremental developments to programs and vastly improved computing power has led to the explosion of the use of QM/MM.

But models are only good if they reflect reality. “That is why computational chemists and experimental chemists talk to each other regularly,” Harvey said, “feeding into each others work.” Thirty years ago this did not happen. The prize recognises how researchers ushered chemistry into the computer age.

First published on The Conversation.

2013 Physics Nobel

October 8, 2013January 25, 2014 Akshat RathiLeave a comment

This time the pundits were right. The 2013 Nobel Prize in Physics was indeed awarded to the discovery of the Higgs boson. Peter Higgs and François Englert shared the prize for suggesting the mechanism that gives subatomic particles their mass.

The Higgs boson is a key part of the Standard Model, which is by far the best theory we have to explain how the universe works at the basic level. If the Higgs boson were not to exist, physicists would have had to go back to the drawing board.

The easiest way to understand the importance of the Higgs boson is to go back to the beginning of the universe. After the Big Bang, for a short time, all particles were massless. But soon after, when the temperature fell below a trillion degrees, the Higgs field switched on. Some particles interacting with this field slowed down and others did not. Those that did such as protons and neutrons gained mass, while others like photons and gluons remained massless. Only when this happened did matter, as we know it now, come to existence in the form of atoms.

This is what Englert and Higgs suggested independently. But others at the time were involved too. In 1964, six physicists came up with similar ideas. First was Englert at the Université Libre de Bruxelles who did it with Robert Brout. Then Higgs at the University of Edinburgh did it on his own. And finally it was a group of three researchers from Imperial College – Thomas Kibble, Gerald Guralnik and Carl Hagen.

These others, many lament, deserved credit too. That though would not have been possible. “It is no surprise that the Swedish Academy felt unable to include us, constrained as they are by a self-imposed rule that the Prize cannot be shared by more than three people,” Kibble said of him and his colleagues. Another candidate would have been Robert Brout, Englert’s colleague, were he still alive.

Still others decried the prize-awarding committee’s exclusion of experimentalists who proved the existence of the Higgs boson. The Large Hadron Collider (LHC) outside Geneva, where these experiments were conducted by the Atlas and CMS teams, was acknowledged in the official citation, but the rules of the prize restrict it to be given only to individuals.

Jon Butterworth of University College London, who was involved in the Higgs experiments at the LHC, wrote:

The discovery of a Higgs boson, showing that the theoretical ideas are manifested in the real world, was thanks to the work of many thousands. There are 3,000 or so people on Atlas, a similar number on CMS, and hundreds who worked on the LHC.

Paul Newman at the University of Birmingham, who is also involved in work at the LHC, said, “At first sight, the Higgs mechanism is a very strange idea.” So it is fitting that, 50 years after the theory was suggested, it took the world’s biggest experiment, thousands of scientists and many billions of pounds to prove the existence of the Higgs boson and thus the Higgs mechanism.

However, the repeated delays in this morning’s announcement of the prize, as the committee debated over who to give the prize to, were a sign that the most-deserved prize will also remain one of the most controversial ones.

First published on The Conversation.

Image credit: CERN