There she blows: the internal ‘magma filter’ that prompts ocean island volcanoes to erupt


Laura Becerril, Author provided

Teresa Ubide, The University of QueenslandThe volcanoes we see on Earth’s surface are just the tip of the iceberg. Beneath the surface, they are fed by a complex network of conduits and reservoirs that bring molten rock, called magma, to the surface.

When the magma erupts, it can generate lava flows that cool down to become volcanic rocks. These rocks hold key clues about volcanoes’ inner workings, and what triggered them to erupt in the past. But decoding these clues is a puzzling task.

Our new research, published in the journal Geology, reveals previously hidden information in the chemistry of erupted lavas. Intriguingly, we discovered that many volcanoes have an internal “filter” that prompts them to erupt.

If we can detect magma at this crucial tipping point inside the volcano, it might even help us detect when an eruption is imminent.

Hotspot volcanoes

Most volcanoes, such as those in the Pacific Ring of Fire and the mid-Atlantic, are at the boundaries between tectonic plates. But some volcanoes, including the ones that created the Hawaiian islands, occur where hot plumes from deep inside Earth reach the surface. These are known as “hotspot” volcanoes.

Australia hosts the longest track of hotspot volcanoes in a continental setting. Over tens of millions of years, volcanoes such as The Glass House Mountains in Queensland, or Wollumbin (Mount Warning) in New South Wales, tracked the movement of the Australian continent over a stationary hotspot.

In the oceans, hotspots build chains of paradise islands such as Hawaii, the Galapagos or the Canary Islands. These ocean island volcanoes were previously thought to have been made of magma that welled up from tens of kilometres beneath the surface, deep in Earth’s mantle.

But our new research suggests ocean island volcanoes may erupt magma that has been filtered and modified at shallower depth.

Crystal-rich, not crystal clear

Volcanic lavas often contain crystals from inside the volcano, that were mixed in with the erupting magma. The crystals tell us a lot about the volcano’s insides, but they can also disguise the chemistry of the lava itself.




Read more:
Volcano crystals could make it easier to predict eruptions


Think of it like rocky road chocolate. If we want to analyse the ingredients of the chocolate itself, we first need to disregard the marshmallows and nuts.

Microscopic image of crystals in magma.
Microscopic image of crystals in magma.
Author provided

We can do this by analysing rocks made from crystal-free lavas. In our study, we compared crystal-free and crystal-rich magmas from El Hierro volcano in the Canary Islands, which last erupted in 2011.

It turns out that the crystal-free magma from these volcanoes is very similar across millions of years of volcanic activity, and across many ocean island volcanoes around the world, including the Canary Islands and Hawaii. This is how we realised the magma was not pristine and coming directly from great depth, but rather filtered at shallower depths.

And if the magma from hotspot island volcanoes is so similar, the chances are their eruptions are triggered by common mechanisms too.

The ‘secret volcano filter’

When crystals form inside the volcano, this “steals” chemical elements from the magma. In turn, this alters the composition of the leftover magma, almost as if it had been passed through a sieve.

This filtering process makes the magma less dense, and increases its gas content. This gas can then bubble up and propel the magma to the surface, just like the cork popping from a bottle of champagne.

In ocean island volcanoes, the magma can reach this “tipping point” at the base of the Earth’s crust, just a few kilometres beneath the surface, rather than at depth.
This means that if we detect magma at this depth with the help of earthquake monitoring equipment, an eruption might follow. This is exactly what happened when El Hierro erupted in 2011.

Does this make it easier to forecast eruptions?

If we could open a volcano like a doll’s house, we would be able to track the movement of magma towards the surface. It’s a pity we can’t, although we can try to “see” this journey indirectly, by monitoring earthquakes, deformation and gas emissions, all of which can indicate magma rising inside a volcano.

But to assess whether a volcano is likely to erupt, or whether a dormant volcano is reawakening, we also need to compare current observations with information about what triggered eruptions in the past.

This is where our new discovery could prove especially useful. If the eruption triggers happen at similar depths in ocean island volcanoes globally, warning signs from such depths may be particularly important to monitor and consider as the precursory signs of eruption.




Read more:
Australia’s volcanic history is a lot more recent than you think


The Conversation


Teresa Ubide, Senior Lecturer in Igneous Petrology/Volcanology, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The ‘pulse’ of a volcano can be used to help predict its next eruption


The 2018 eruption of Kilauea volcano was preceded by damage of the magma plumbing system at the summit.
Courtesy of Grace Tobin, 60 Minutes, Author provided

Rebecca Carey, University of Tasmania

Predicting when a volcano will next blow is tricky business, but lessons we learned from one of Hawaii’s recent eruptions may help.

Kīlauea, on the Big Island of Hawai’i, is probably the best understood volcano on Earth. That’s thanks to monitoring and gathered information that extends back to the formation of the Hawaiian Volcano Observatory in 1912.

The volcano is also subject to the world’s most technologically advanced geophysical monitoring network.




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From Kilauea to Fuego: three things you should know about volcano risk


From the skies, satellites collect data that show the changing topography of the volcano as magma moves throughout the internal magma plumbing system. Satellites also look at the composition of volcanic gases.

From the ground, volcanologists use a number of highly sensitive chemical and physical tools to further understand the structure of that magma plumbing system. This helps to study the movement of magma within the volcano.

Earthquakes and vibrations

A lynch pin of volcano monitoring is seismicity – how often, where and when earthquakes occur. Magma movement within the volcano triggers earthquakes, and putting together the data on their location (a technique known as triangulation) tracks the path of magma underground.

A schematic of the deep magma plumbind system of Kilauea volcano, Big Island, Hawaii. Magma is transported from deep within the Earth and arrives in a series of summit magma reservoirs.
USGS

A newer technique, seismic interferometry, uses vibrations of energy from ocean waves hitting the distant shorelines that then travel through the volcano.

Changes in the speed of these vibrations help us map the 3D footprint of the volcano’s magma plumbing system. We can then detect when, and in some cases how, the magma plumbing system is changing.

This monitoring provides the “pulse” of the volcano during times of inactivity – a baseline from which to detect change during volcanic unrest. This proved invaluable for early warning, and the prediction of where and when, of the eruption of Kīlauea on May 3, 2018.

The “pulse” of Kīlauea includes cycles of volcano inflation (bulging) and deflation (contraction) as magma moves into and out of the storage region at the summit of the volcano.

The speeds of vibrations travelling through the volcano are predictable during observations of inflation/deflation cycles. When the volcano bulges, the vibrations travel faster through the volcano as rock and magma is compressed. When the volcano contracts these speeds decrease.

We describe this relationship between the two sets of data – the bulging/contraction and the faster/slower speed of vibrations – as coupled.

Something changed

Compared to our baseline, we saw the coupled data shift 10 days before the Kīlauea eruption on May 3. That told scientists the magma plumbing system had changed in a significant way.

The volcano was bulging due to the buildup of pressure inside the magma chamber, but the seismic waves were slowing down quite dramatically, instead of speeding up.

Our interpretation of this data was that the summit magma chamber was not able to sustain the pressure from an increasing magma supply – the bulge was too big. Rock material started to break around the summit magma chamber.

Breakage of the rocks perhaps then led to changes of the summit magmatic system so that more magma could more easily arrive at the eruption site about 40km away.

As well as Kīlauea, such coupled data sets are regularly collected, investigated and interpreted in terms of magma transport at other volcanoes globally. Sites include Piton de la Fournaise on Reunion Island, and Etna volcano, Italy.

But our modelling was the first to demonstrate these changes in the coupled data relationship could occur due to weakening of the material inside the volcano before an eruption.

The damage model that we applied can now be used for other volcanoes in a state of unrest. This adds to the toolbox volcanologists need to predict the when and where of an impending eruption.

So much data, we need help

When volcanoes are in a heightened state of unrest, the volume of information available from digital data and ground observations is extreme. Scientists tend to rely on observational monitoring first, and other data when time and extra people are available.

But the total amount of incoming data (such as from satellites) is overwhelming, and scientists simply can’t keep up. Machine learning might be able to help us here.

Artificial intelligence is the new kid on the block for eruption prediction. Neural networks and other algorithms can use high volumes of complex data and “learn” to distinguish between different signals.




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Automated early alert systems of an impending eruption using sensor arrays exist for some volcanoes today, for example at Etna volcano, Italy. It’s likely that artificial intelligence will make these systems more sophisticated in the future.

Early detection sounds wonderful for authorities charged with public safety, but many volcanologists are wary.

If they lead to multiple false alarms then that could slash trust in scientists for both managers of volcanic crises and the public alike.The Conversation

Rebecca Carey, Senior Lecturer in Earth Sciences, University of Tasmania

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Curious Kids: Why do volcanoes erupt?


File 20180619 126537 gka5w8.jpg?ixlib=rb 1.1
Some explosive volcanoes can send ash high up into the sky and it can travel around the world over different countries.
Shutterstock

Heather Handley, Macquarie University

This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky! You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.


Why do volcanoes erupt? – Nicholas, age 3 years and 11 months, Northmead, NSW.


The rock inside the planet we live on can melt to form molten rock called magma. This magma is lighter than the rocks around it and so it rises upwards. Where the magma eventually reaches the surface we get an eruption and volcanoes form.

The top part of the Earth is made up of a number of hard pieces called tectonic plates. Magma and volcanoes often form where the plates are pulled apart or pushed together but we also find some volcanoes in the middle of tectonic plates.




Read more:
Curious Kids: why doesn’t lava melt the side of the volcano?


Volcanoes have many different shapes and sizes, some look like steep mountains (stratovolcanoes), others look like bumps (shield volcanoes) and some are flat with a hole (a crater or caldera) in the centre that is often filled with water.

The shape of the volcano and how explosively it erupts depend largely on how “sticky” and how “fizzy” (how much gas) the magma is that is erupted.

For example, if you try to blow bubbles in cooking oil though a straw, the bubbles can escape quite easily because the cooking oil is runny.

If you try to blow bubbles in jam or peanut butter you would find it very difficult because the jam and peanut butter are very sticky, they wouldn’t move much at all if you tried to pour them out of the jar.

It is the same with volcanoes. When magma rises towards the surface gas bubbles start to form. Whether or not they can escape as the magma is rising affects how explosive the eruption will be.

Where the magma is runny like cooking oil and doesn’t have much bubbly gas mixed in it, such as places like Hawaii, then we see lots of slow-moving lava flows and shield volcanoes. Lava is what we call magma when it reaches the surface.

Here are some pictures of a recent Hawaiian eruption:

However, where the magma is very sticky, like jam or peanut butter, and if it contains a lot of bubbly gas then the gas can get stuck and eruptions can be very powerful and explosive, like the recent eruptions at Fuego volcano in Guatemala.

Damage caused by eruptions

In explosive eruptions the frothy, bubbly magma can be ripped apart into tiny bits called volcanic ash. This is not ash like you get after a barbecue or fire, it does not crumble away in your fingers. It is very sharp and is dangerous to breathe in.

Some explosive volcanoes can send ash high up into the sky and it can travel around the world over different countries. If aeroplanes travel through an ash cloud from a volcano it can cause a lot of damage to the engine.

Other explosive eruptions create fast-moving, hot clouds of volcanic ash, gas and rocks that travel down the sides of the volcanoes and destroy pretty much everything in their path.

The benefits of volcanoes

Despite the great damage they can cause, volcanoes also help us to live. Volcanic ash provides food for the soil around volcanoes which helps us grow plants to eat. The heat from some volcanoes is used to make energy to power lights, fridges, televisions and computers in people’s houses.

You can find some more information about different types of volcanoes here and here.




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Curious Kids: Do most volcanologists die from getting too close to volcanoes?


Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. They can:

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Heather Handley, Associate Professor in Volcanology and Geochemistry, Macquarie University

This article was originally published on The Conversation. Read the original article.

Climate Change: Bringing on Disasters


The link below is to an article reporting on suggestions that climate change may bring on volcanic eruptions, earthquakes and tsunamis.

For more visit:
http://www.smh.com.au/environment/climate-change/climate-change-is-set-to-shake-the-earth-20120228-1tzr2.html