Posts Tagged ‘volcano’

The horse, a purebred, was wearing a bronze-plated military saddle and ready to go when Mount Vesuvius erupted and buried the ancient city of Pompeii in A.D. 79. The horse, too, was covered in pumice and ash.

Almost 2,000 years later, archaeologists unearthed the immobilized horse, along with the remains of two others, in the remnants of a stable attached to a sumptuous suburban villa in Civita Giuliana, outside the walls of what remains of Pompeii, the Archaeological Park of Pompeii said in a statement on Monday.

The horses are among a growing list of archaeological treasures dug up at the Pompeii site, discovered in the late 16th century. This year, Pompeian excavations have found a shrine with wall paintings that hint at Roman life in the first century; the skeleton of a man who had fled the volcanic eruption only to be buried by a rock; and a well-preserved fresco in a house on the Via del Vesuvio depicting the mythological rape of Leda, the queen of Sparta, by Zeus in the form of a swan.

The horses probably perished soon after the volcanic explosion, with their frozen postures suggesting they had been unable to wrest free. The saddled horse and its elaborate harness were discovered over the summer, the archaeological park statement said.

Instead of stirrups, the saddle had four bronze-plated wooden horns, one in each corner, to help keep the rider stable. Researchers compared the saddle to those used by Romans around the time Mount Vesuvius erupted.

In May, researchers completed a plaster cast of the first horse found at the site. The dimensions suggested that the horses, including the latest discovered, had been of a valuable breed, officials said in a statement, a type used to display social status.

The discovery of the horses confirmed that the stable had been part of a prestigious estate, Massimo Osanna, the Pompeii site’s general director, said in the statement. The villa was enhanced with “richly frescoed and furnished rooms, and sumptuous sloping terraces facing onto the Gulf of Naples and Capri, as well as an efficient servant’s quarter, with a farmyard, oil and wine warehouses and densely cultivated lands,” according to the statement.

Archaeologists discovered 15 rooms from the villa in the early 20th century, and smaller finds since then. In 1955, dividing walls were found in excavations at Civita Giuliana. In recent decades, scavengers visited the site too, digging illegal tunnels below the estate.

To stop the illegal tunneling, official excavations began again this year. In 2019, with the aid of 2 million euros ($2.27 million), archaeologists will continue the work with an eye toward opening the site to the public, Mr. Osanna said.

Large boulders 2 metres across and weighing 10 tonnes could soon begin blasting out from Kilauea, the erupting volcano on Hawaii’s Big Island. But the biggest imminent threat to residents could arise if the volcano starts spewing ash to heights of 6000 metres or more.

The conditions are similar to those when Kilauea last erupted in 1924, which showered the island in ash for several months. “That’s what I would guess will happen next,” said Don Swanson of the Hawaiian Volcano Observatory, in a press conference video issued on 9 May.

Kilauea has been unusually active since late April. On 30 April, the floor of the lava lake at the volcano’s summit collapsed.

The lava has been draining ever since. By 9 May, and following a 6.9-magnitude earthquake on 3 May, it had already plunged almost 300 metres into the vertical shaft below. The lava is now below the level of water-saturated rock at 600 metres above sea level. “Since the earthquake, the lava lake has dropped in a very steady manner, at 2.2 metres per hour,” said Swanson.

Steam explosions

Because the lava has sunk so low, water is now draining into the empty shaft that it previously occupied. The walls of the crater are red hot, so the water is instantly turning to steam, which is now bellowing in white clouds from the volcano summit.

What happens next is difficult to predict, said Swanson. But there could be explosions. If large rocks fall from the unstable walls of the shaft, they could block it, in which case pressure from steam will build up underneath and cause an explosion.

Once the “plug” is blown out, the steam can escape again unimpeded, until the plug is restored by rock falls.

The result would be a series of explosions followed by hiatuses. That’s what happened in 1924: there were 60 explosions over the course of four months or so.

Boulders and ash

Any explosion can produce a variety of “ejecta”, said Swanson. “You can get rocks ejected like cannonballs, weighing up to 10 tonnes and 2 [metres] in diameter,” he said.

The good news is that these boulders should fall within about a kilometre of the summit. This area is deserted. Smaller rocks the size of softballs could impact a bit further away, albeit still not far enough to reach people’s homes. But tinier fragments a fraction of an inch wide could reach peopled areas. “They would sting, but not be lethal,” says Swanson.

The most important hazard is fine ash, which can block thoroughfares and accumulate on buildings. In 1924, ash landed on railway tracks and made them too slippery for trains to run on safely.

“It’s a nuisance, especially if it goes on for several weeks,” said Tina Neal of the Hawaiian Volcano Observatory at the press conference. “I’ve been in many ash falls myself, and the most difficult bit is keeping it out of your eyes.”

Meanwhile, lava fountains and steam continue to spew copiously from cracks on the island, reaching heights of 30 metres. By Monday, there were 19 fissures in total. So far, more than 30 properties have been destroyed by lava, and 2000 residents remain evacuated.

https://www.newscientist.com/article/2168913-hawaiis-erupting-volcano-may-blast-out-10-tonne-cannonballs/

by ROBERT KRULWICH

Add all of us up, all 7 billion human beings on earth, and clumped together we weigh roughly 750 billion pounds. That, says Harvard biologist E.O. Wilson, is more than 100 times the biomass of any large animal that’s ever walked the Earth. And we’re still multiplying. Most demographers say we will hit 9 billion before we peak, and what happens then?

Well, we’ve waxed. So we can wane. Let’s just hope we wane gently. Because once in our history, the world-wide population of human beings skidded so sharply we were down to roughly a thousand reproductive adults. One study says we hit as low as 40.

Forty? Come on, that can’t be right. Well, the technical term is 40 “breeding pairs” (children not included). More likely there was a drastic dip and then 5,000 to 10,000 bedraggled Homo sapiens struggled together in pitiful little clumps hunting and gathering for thousands of years until, in the late Stone Age, we humans began to recover. But for a time there, says science writer Sam Kean, “We damn near went extinct.”

I’d never heard of this almost-blinking-out. That’s because I’d never heard of Toba, the “supervolcano.” It’s not a myth. While details may vary, Toba happened.

Toba, The Supervolcano

Once upon a time, says Sam, around 70,000 B.C., a volcano called Toba, on Sumatra, in Indonesia went off, blowing roughly 650 miles of vaporized rock into the air. It is the largest volcanic eruption we know of, dwarfing everything else…

That eruption dropped roughly six centimeters of ash — the layer can still be seen on land — over all of South Asia, the Indian Ocean, the Arabian and South China Sea. According to the Volcanic Explosivity Index, the Toba eruption scored an “8”, which translates to “mega-colossal” — that’s two orders of magnitude greater than the largest volcanic eruption in historic times at Mount Tambora in Indonesia, which caused the 1816 “Year Without a Summer” in the northern hemisphere.

With so much ash, dust and vapor in the air, Sam Kean says it’s a safe guess that Toba “dimmed the sun for six years, disrupted seasonal rains, choked off streams and scattered whole cubic miles of hot ash (imagine wading through a giant ashtray) across acres and acres of plants.” Berries, fruits, trees, African game became scarce; early humans, living in East Africa just across the Indian Ocean from Mount Toba, probably starved, or at least, he says, “It’s not hard to imagine the population plummeting.”

Then — and this is more a conjectural, based on arguable evidence — an already cool Earth got colder. The world was having an ice age 70,000 years ago, and all that dust hanging in the atmosphere may have bounced warming sunshine back into space. Sam Kean writes “There’s in fact evidence that the average temperature dropped 20-plus degrees in some spots,” after which the great grassy plains of Africa may have shrunk way back, keeping the small bands of humans small and hungry for hundreds, if not thousands of more years.

So we almost vanished.

But now we’re back.

It didn’t happen right away. It took almost 200,000 years to reach our first billion (that was in 1804), but now we’re on a fantastic growth spurt, to 3 billion by 1960, another billion almost every 13 years since then, till by October, 2011, we zipped past the 7 billion marker, says writer David Quammen, “like it was a “Welcome to Kansas” sign on the highway.”

In his new book Spillover, Quamman writes:

We’re unique in the history of mammals. We’re unique in this history of vertebrates. The fossil record shows that no other species of large-bodied beast — above the size of an ant, say or an Antarctic krill — has ever achieved anything like such abundance as the abundance of humans on Earth right now.
But our looming weight makes us vulnerable, vulnerable to viruses that were once isolated deep in forests and mountains, but are now bumping into humans, vulnerable to climate change, vulnerable to armies fighting over scarce resources. The lesson of Toba the Supervolcano is that there is nothing inevitable about our domination of the world. With a little bad luck, we can go too.

We once almost did.

http://www.npr.org/sections/krulwich/2012/10/22/163397584/how-human-beings-almost-vanished-from-earth-in-70-000-b-c

Researchers claim to have worked out how to accurately predict the eruption of ‘supervolcanoes’ that blanket the earth in giant ash clouds triggering a ‘nuclear winter’.

They say the discovery could reveal exactly when giant pools of magma greater than 100 cubic miles in volume and formed a few miles below the surface will erupt.

Repeatedly throughout Earth’s history,when they become a super-eruption, the resulting gigantic volcanic outbursts that throw 100 times more superheated gas, ash and rock into the atmosphere than run-of-the-mill eruptions – enough to blanket continents and plunge the globe into decades-long volcanic winters.

The most recent super-eruption took place about 27,000 years ago in New Zealand, well before humans kept records of volcanic eruptions and their aftermath.

Geologists today are studying deposits from past super-eruptions to try and understand where and how rapidly these magma bodies develop and what causes them to eventually erupt.

Despite considerable study, geologists are still debating how quickly these magma pools can be activated and erupted, with estimates ranging from millions to hundreds of years.

Now a team of geologists have developed a new ‘geospeedometer’ that they argue can help resolve this controversy by providing direct measurements of how long the most explosive types of magma existed as melt-rich bodies of crystal-poor magma before they erupted.

They have applied their new technique to two super-eruption sites and a pair of very large eruptions and found that it took them no more than 500 years to move from formation to eruption.

These results are described in the article ‘Melt inclusion shapes: Timekeepers of short-lived giant magma bodies’ appearing in the November issue of the journal Geology.

Geologists have developed a number of different ‘timekeepers’ for volcanic deposits.

The fact that these techniques measure different processes and have different resolutions, has contributed to this lack of consensus.

‘Geologists have developed a number of different ‘timekeepers’ for volcanic deposits,’ said Guilherme Gualda, associate professor of earth and environmental sciences at Vanderbilt University, who directed the project.

‘The fact that these techniques measure different processes and have different resolutions, has contributed to this lack of consensus.

‘Our new method indicates that the process can take place within historically relevant spans of time,’
The method was developed as part of the doctoral thesis of Ayla Pamukcu, who is now a post-doctoral researcher at Brown and Princeton Universities.

‘The hot spot under Yellowstone National Park has produced several super-eruptions in the past.

‘The measurements that have been made indicate that this magma body doesn’t currently have a high-enough percentage of melt to produce a super-eruption.

But now we know that, when or if it does reach such a state, we will only have a few hundred years to prepare ourselves for the consequences,’ Gualda said.

The researchers’ geospeedometer is based on millimeter-sized quartz crystals that grew within the magma bodies that produced these giant eruptions.

Quartz crystals are typically found in magmas that have a high percentage of silica.

This type of magma is very viscous and commonly produces extremely violent eruptions. Mount St. Helens was a recent example.

When the crystals form, they often capture small blobs of molten magma – known as blebs or melt inclusions. Blebs are initially round.

While the crystal is floating in hot magma, diffusion causes them to gradually acquire the polygonal shape of the crystal void that they occupy. But this faceting process can be halted if eruption occurs before complete faceting is achieved.

Using advanced 3-D X-ray tomography, the researchers were able to measure the size and shape of the melt inclusions with exquisite precision.

In cases where the inclusions had not become completely faceted, the researchers could determine how much time had elapsed since they were enclosed.

‘Previous studies provided us with the data we needed to calculate the rate of the faceting process. We then used this rate, in combination with our shape measurements, to calculate how long the crystal existed in the magma before the eruption,’ said Pamukcu.

In addition, the researchers compared the results obtained with faceting with results obtained using other techniques.

Crystallization may cause variations in concentration of certain elements. In quartz, the element titanium can vary sharply between different zones or layers within the crystal.

Over time, however, the process of diffusion gradually smooths out these variations.

This process also stops at the eruption, so the shallower the slope of titanium concentrations across these boundaries today, the longer the crystal spent in magmatic conditions.

The physics of this process is also well known, so the researchers could use these measurements to provide an independent estimate of how long a crystal spent floating around in the melt.

They found that the duration times they derived from the titanium diffusion measurements agreed closely with those produced by the faceting method.

‘Our current method will also work on smaller volcanic systems, as long as they erupt magmas that contain quartz crystals,’ said Pamukcu.

‘We are also confident that we can adapt these techniques to work with other minerals, which will allow us to make similar timescale calculations for other types of magmas and volcanoes, like the low-silica basalts commonly erupted from Hawaiian volcanoes.’

Read more: http://www.dailymail.co.uk/sciencetech/article-3281859/Phew-Scientists-claim-developed-predict-cataclysmic-SUPERVOLCANO-eruptions-end-life-Earth.html#ixzz3pD81J9cT

Brennan Phillips and some colleagues were recently on an expedition to Kavachi volcano, an active underwater volcano near the Solomon Islands in the South Pacific. But they weren’t prepared for what they saw deep inside the volcanic crater:

Sharks!

Hammerheads and silky sharks, to be specific, contentedly swimming around despite the sizzling water temperatures and biting acidity.

Volcanic vents such as these can release fluids above 800 degrees Fahrenheit and have a similar acidity to vinegar, according to the Marine Education Society of Australasia.

“The idea of there being large animals like sharks hanging out and living inside the caldera of the volcano conflicts with what we know about Kavachi, which is that it erupts,” Phillips, a biological oceanography Ph.D. student at the University of Rhode Island.

This brings up some perplexing questions about what the animals do if the volcano decides to wake up:

“Do they leave?” Phillips asks. “Do they have some sign that it’s about to erupt? Do they blow up sky-high in little bits?”

The volcano wasn’t erupting when Phillips’ team arrived, meaning it was safe to drop an 80-pound camera into the water to take a look around. After about an hour of recording, the team fished the camera out and watched the video.

First, the video showed some jellyfish, snappers, and small fish. Then, a hammerhead swam into view, and the scientists erupted in cheers. They also saw a cool-looking stingray.

http://www.businessinsider.com/sharks-found-swimming-near-active-underwater-volcano-2015-7