UPDATE :Submarine Volcanoes: Expedition Sheds Light On Eruptions


http://earthchangesmedia.com/update-submarine-volcanoes-expedition-sheds-light-on-eruptions
Some of the world’s biggest and most powerful volcanoes probably lie not on land but deep beneath the ocean waves. Occupying vast stretches of ocean floor, chains of these submarine volcanoes may extend for hundreds or even thousands of kilometres.
Havre volcano forms part of one such…

Some of the world’s biggest and most powerful volcanoes probably lie not on land but deep beneath the ocean waves. Occupying vast stretches of ocean floor, chains of these submarine volcanoes may extend for hundreds or even thousands of kilometres.

Havre volcano forms part of one such chain, known as the Kermadec Arc, which runs north of Auckland, in New Zealand.

Little is known about this very deep volcano, more than 700 metres below sea level. It last erupted in 2012, a relatively rare event that has prompted 17 scientists from 11 institutions and five countries to set off on an expedition to study Havre’s eruption products and new volcanic architecture.

“We are using a remotely operated vehicle, named Jason, and an autonomous underwater vehicle, Sentry, to map the volcano’s new post-eruption topography and the different rock types that erupted,” says co-chief expedition scientist and University of Tasmania researcher Rebecca Carey. “By studying deposits on the volcano, we are able to understand the nature of the eruption and the source vents responsible for it.”

She and the team are using Jason to collect a range of samples from different areas. These will be analysed to help understand the volcano’s eruption dynamics. “For example, we’ll be able to tell how fast the magma ascended to the surface from deep within the earth, and what factors drove explosive or oozing lava eruptions,” Dr Carey says.

Roughly three-quarters of the earth’s volcanism takes place on the sea floor, she says. “By studying this eruption, we’ll be better equipped to understand how submarine volcanoes like Havre erupt and disperse their products in and around the ocean.”

Rare event

Earth scientists understand very little about these eruptions, which are rarely detected. This is because the pressure exerted by the tremendous volume of overlying water suppresses the volcanoes’ explosivity.

“In July 2012, when Havre last erupted from vents at depths of more than 900 metres, the blast was so powerful that the eruption plume made it to the sea surface, from where it was detected by satellite imagery,” Dr Carey says. “”We therefore have this unique opportunity to access 2012 eruption products from known source vents at different depths, constraints which will make a significant contribution to earth and marine science.”

Remapping

Havre volcano and the surrounding ocean floor were mapped in 2002, and after the eruption the floor was remapped. “Our survey found multiple new vents that ranged in depth between 700 and 1500 metres below sea level,” Dr Carey says.

A preliminary estimate suggested that up to two cubic kilometres of volcanic pumice had been erupted. “A cube with edges one-and-quarter kilometres long is a little hard to imagine, but this is equivalent to the volume of 1000 MCG stadiums,” Sydney University Professor Tom Hubble says.

“As the largest and deepest submarine silicic eruption ever documented, this was likely to be a ‘once in a century’ event,” Dr Carey said. “It was roughly the size of the renowned Mount St Helens eruption of 1980, and perhaps more than 10 times bigger than the 2010 Eyjafjallajokull eruption in Iceland.”

Lowdown on lava
“Fresh lava flows over the deep sea floor all the time, geologically speaking,” Professor Hubble says.

An example of this phenomenon is the early submarine phase of lava effusion from basaltic volcanoes such as those of the Hawaiian seamount chain. “However, these basalt magmas have relatively low quantities of silica, and are therefore much more fluid than the high-silica magmas erupted from the Havre volcanic vents,” he says.

The enormous confining pressure created by kilometres of water above the volcanic vent also helps restrict the expansion of dissolved gases in the lava and makes them more fluid than they would be at atmospheric pressure.

“Carbon-dioxide and superheated steam is nearly always mixed in with silicate magma and, at low pressures, these gases can expand rapidly and cause catastrophic, explosive volcanism,” Professor Hubble says.

The Havre volcanic eruption demonstrates that this high-silica magma released a large enough volume of volcanic gas to drive explosive eruptions at depths of at least 900 metres.

Before this event, the deepest recorded eruption of a high-silica, viscous-magma type of volcano had been at 250 to 300 metres below sea level. “So the 2012 eruption was unique and presented an exciting opportunity for frontier science,” Dr Carey says.

Crustal plates

Beneath the earth’s relatively thin, rigid crust lies a mantle of solid crystalline rock. At a depth of more than 100 kilometres, the rock is so hot that it’s malleable and can flow a bit like plasticene does when you bend it, but very, very slowly.

Over aeons, the covering crust has broken into massive brittle sections called plates. There are seven main plates and several smaller crustal plates all moving and shoving against each other as they slide across the hot, soft mantle.

The plates are continuously colliding and being forced under one another, a process called subduction. Occasionally they fracture, causing earthquakes. The melting of the subducting crust provides magmas for volcanoes, including submarine volcanoes.

Eruptions explained

Caldera volcanoes, such as the one at Havre, are the surface expression of magma “plumbing” systems that lie deep within the planet’s crust. Most of the world’s large volcanoes, occurring on plate boundaries, are fed by magma from the earth’s upper mantle and lower crust.

Magma originating from earth’s mantle gets stored in chambers several kilometres below the surface. Pressure builds as more magma enters the system, resulting in fracturing of the crust. Eventually the pressure gets too great and magma accelerates to the surface, where it erupts.

Yet the eruption of magma deep beneath the ocean remains something of a mystery. “This is because, until now, many of the world’s submarine volcanic arcs have remained largely unexplored,” Dr Carey says.

Caldera volcanoes are typically the source of the largest eruptions on earth. “They spew out vast quantities of very viscous magmas, which drain underlying magma reservoirs. The inward collapse of a reservoir can repressurise the remaining magma and boost explosivity and the rate at which magma discharges,” she says.

Types

Volcanoes come in several forms: active (erupting regularly, including today), dormant (no sign of activity for many years, but likely to erupt again) and extinct (no sign of activity for ages). Some experts say there should probably be a fourth category, “erupting”, to indicate dangerous and currently ongoing volcanism.

The Kermadec Arc hosts numerous caldera volcanoes and is particularly active.

Pumice from the eruption has landed on Australian shores since April 2013, says Dr Carey. “It has been slowly making its way down the Australian east coast and finally it arrived in Tasmania in March 2014.”

By the time it reached Tasmanian shores, some of the pumice had acquired a biological cargo of up to 80 marine “hitchhiker” species, including a colourful collection of barnacles, molluscs, corals, crabs, anemones and bristle worms. “As a result, the pumice is sometimes white, brown or black,” Dr Carey says.

Rock record

Vulcanologists use a volcano’s eruption history, as recorded in rocks, to get a better idea of when and how it might erupt again.

The best way to predict this is through intensive monitoring of earthquake activity, changes in heat flow and distribution, the build-up of stresses in overlying rocks, groundwater temperatures and gas emissions, says Museum Victoria earth scientist Bill Birch.

Although it is an inexact science, vulcanology may gain some predictive power as a result of research published recently in the British journal Nature.

The research reveals that the earth’s subterranean plumbing system opens up and allows a relatively rapid and efficient transfer of magma from the zone of production in the lower crust and upper mantle to the near-surface magma chambers beneath a volcano.

The new work shows that this transfer of magma occurs on timescales of months, years or decades as opposed to the multi-centurial and multi-millennial scales envisaged by previous generations of geologists. “This means that continual and careful monitoring of ground surface shape and the background low-level seismic movements near dormant volcanoes might help pinpoint magma moving in the subsurface,” Dr Birch says.

Large volcanic eruptions on land are usually preceded by uplift of the ground-surface as magma from chambers tens of kilometres down is transferred to higher chambers, two or three kilometres beneath the surface.

Volcanoes often signal their reawakening from a dormant state with steam blasts and small eruptions of ash which increase in intensity over months to years.

As the ground swells, the volcanic plumbing system usually unclogs as well. Steam blasts open the conduits linking the near-surface magma chamber to the volcano.

Rhythmic earthquake activity, known as harmonic tremor, records magma movement in the earth’s crust and often accompanies such events, Dr Birch says. “These processes build up and fall away – and then build-up again, several or even tens of times before an eruption takes place.”

Related posts:

Advertisements

About Earth Changes Media w/ Mitch Battros

Mitch Battros is a scientific journalist who is highly respected in both the scientific and spiritual communities due to his unique ability to bridge the gap between modern science and ancient text. Founded in 1995 – Earth Changes TV was born with Battros as its creator and chief editor for his syndicated television show. In 2003, he switched to a weekly radio show as Earth Changes Media. ECM quickly found its way in becoming a top source for news and discoveries in the scientific fields of astrophysics, space weather, earth science, and ancient text. Seeing the need to venture beyond the Sun-Earth connection, in 2016 Battros advanced his studies which incorporates our galaxy Milky Way - and its seemingly rhythmic cycles directly connected to our Solar System, Sun, and Earth driven by the source of charged particles such as galactic cosmic rays, gamma rays, and solar rays. Now, "Science Of Cycles" is the vehicle which brings the latest cutting-edge discoveries confirming his published Equation.
This entry was posted in Uncategorized and tagged . Bookmark the permalink.