Traveling through the volcanic conduit

This is Mt. St. Helens in Washington. -  Josef Dufek
This is Mt. St. Helens in Washington. – Josef Dufek

How much ash will be injected into the atmosphere during Earth’s next volcanic eruption? Recent eruptions have demonstrated our continued vulnerability to ash dispersal, which can disrupt the aviation industry and cause billions of dollars in economic loss. Scientists widely believe that volcanic particle size is determined by the initial fragmentation process, when bubbly magma deep in the volcano changes into gas-particle flows.

But new Georgia Tech research indicates a more dynamic process where the amount and size of volcanic ash actually depend on what happens afterward, as the particles race toward the surface. Their initial size and source depth, as well as the collisions they endure within the conduit, are the differences between palm-sized pumice that hit the ground and dense ash plumes that jet into the atmosphere and can halt aviation. The findings are published in the current edition of Nature Geoscience.

Assistant Professor Josef Dufek used lab experiments and computer simulations to study particle break-up, known as granular disruption, in volcanic eruptions. His team, which included the University of California, Berkeley’s Michael Manga and Ameeta Patel, determined that shallow (approximately 500 meters below the surface) fragmentation levels likely cause abundant, large pumice that are often seen in large volcanic eruptions. If the fragmentation begins a few kilometers underground, the volcano is more likely to emit fine-grained ash.

“The longer these particles stay in the conduit, the more often they collide with each other,” said Dufek, a faculty member in Georgia Tech’s School of Earth and Atmospheric Sciences. “These high-energy collisions break the volcanic particles into fractions of their original size. That’s why deeper fragmentations produce small particles. Particles that begin closer to the surface with less energy don’t have time for as many collisions before they exit the volcano. They stay more intact, are larger and often contained in pyroclastic flows.”

The team collected volcanic rock from California’s Medicine Lake volcanic deposit for collision experiments. They also used glass spheres because, like glass, pumice is heated and hardens before crystals are able to form. Using a pumice gun that propels volcanic fragments using compressed gases, Dufek and his team determined that particles must collide at a minimum of 30 meters per second to break into larger pieces.

Using numerical simulations, the researchers concluded that large pumice particles (greater than fist size) will not likely remain intact unless the fragmentation is very shallow. Abundant large pumice rocks in a deposit provide an indication of the depth of fragmentation, which may vary over the course of the eruption. Due to the depth and violent nature of the process, scientists have had little record of the depth of the fragmentation process, even though much of the eruptive dynamics and subsequent hazards are determined in this process.

Dufek and his team will next use the research to better understand the dynamics of one of the most rare natural disasters: super volcanoes, which produced the features in Yellowstone National Park.

“We know very little about the eruption processes during super eruptions,” said Dufek. “Indications of their fragmentation levels will provide important clues to their eruptive dynamics, allowing us to study them in new ways.”

Scientists ‘read’ the ash from the Icelandic volcano 2 years after its eruption

The models aim to predict the evolution of volcanic ash clouds, like the one emitted by Eyjafjallajökull. -  FLEXPART/NILU.
The models aim to predict the evolution of volcanic ash clouds, like the one emitted by Eyjafjallajökull. – FLEXPART/NILU.

In May 2010, the ash cloud from the Icelandic volcano Eyjafjallajökull reached the Iberian Peninsula and brought airports to a halt all over Europe. At the time, scientists followed its paths using satellites, laser detectors, sun photometers and other instruments. Two years later they have now presented the results and models that will help to prevent the consequences of such natural phenomena.

The eruption of the Eyjafjallajökull in the south of Iceland began on the 20 March, 2010. On the 14 April it began to emit a cloud of ash that moved towards Northern and Central Europe, resulting in the closure of airspace. Hundreds of planes and millions of passengers were grounded.

After a period of calm, volcanic activity intensified once again on the 3 May. This time the winds transported the aerosols (a mixture of particles and gas) towards Spain and Portugal where some airports had to close between the 6 and 12 May. This was also a busy time for scientists who took advantage of the situation to monitor the phenomenon. Their work has now been published in the Atmospheric Environment journal.

“The huge economic impact of this event shows the need to describe with precision how a volcanic plume spreads through the atmosphere. It also highlighted the importance of characterizing in detail its particles composition and establishing its concentration limits to ensure safe air navigation,” explains Arantxa Revuelta, researcher at the Spanish Research Centre for Energy, Environment and Technology (CIEMAT).

The team identified the volcanic ash cloud as it passed over Madrid thanks to LIDAR (Light Detection and Ranging), the most effective system for assessing aerosol concentration at a height. The CIEMAT station is one of 27 belonging to the European network EARLINET (European Aerosol Research Lidar Network) that use this instrument. Its members have also published a publicly accessible article on the matter in the Atmospheric Chemistry and Physics journal.

Using LIDAR technology, scientists direct a laser beam towards the sky, like a saber in Star Wars. The signal reflected back from particles provides information on their physical and chemical properties. A maximum aerosol value of 77 micrograms/m3 was estimated, which as a concentration is below the risk value established for air navigation (2 miligrams/m3).

Furthermore, the levels of particles rich in sulphates shot up even though they were fine particles (with a minimum diameter of 1 micra). This meant that they were much smaller than those particles over 20 micra found in countries in Central Europe.

These thicker particles are generally considered to be ‘ash’ and can really damage aircraft motors. The fine matter, like that detected over the Iberian Peninsula, is similar to that commonly found in urban and industrial areas. It is subject to study more for its damaging health effects rather than its impact on air navigation.

NASA’s network of sun photometers

It is important to track the evolution of all the particles in order to provide information to managers responsible for this kind of crisis. Working in this field were members of NASA’s AERONET (AErosol RObotic NETwork) network, which is made up by the different tracking stations in Spain and Portugal (integrated into RIMA) equipped with automatic sun photometers. These instruments focus towards the sun and collect data each hour on the aerosol optical thickness and their distribution by size in the atmospheric column.

The combined use of sun photometers and LIDAR technology boosts data collection. For example, the station in Granada and Évora revealed that the volcanic ash cloud circulated between 3 km and 6 km above the ground.

“Instruments like LIDAR are more powerful on an analytical level but their spatial and weather coverage is low. This means that sun photometers come in very useful in identifying volcanic aerosols when no other measures are available,” outlines the researcher Carlos Toledano from the University of Valladolid and member of the AERONET-RIMA network.

From their stations it was confirmed that “there is great variation between the size and characteristics of the volcanic aerosol particles over successive periods.” This was also verified by members of another European Network, EMEP (European Monitoring and Evaluation Program), which traces atmospheric pollution and is managed in Spain by the National Meteorological Agency. This group confirmed an increase in aerosols and their sulphate concentrations over the Iberian Peninsula and recorded the presence of sulphur dioxide from the Icelandic volcano.

Models and Predictions

The large part of observations of Eyjafjallajökull’s eruption, which were taken from aeroplanes, satellites or from earth, helped scientists validate their prediction and particle dispersion models.

“During the management of the crisis it became evident that there are still no precise models that provide real time data for delimiting an affected airspace, for example,” admits Toledano. Nevertheless, his team put the FLEXPART model to test using empirical data. From the Norwegian Institute for Air Research (NILU), it managed to calculate the arrival of volcanic ash in certain situations.

The powerful equipment available at the Barcelona Supercomputing Center (BSC-CNS) was used on this occasion to validate a model which had been developed at the centre: the Fall3d. As one of the authors Arnau Folch states, “the model can be applied to the dispersion of any type of particle. But, in practice, it has been especially designed for particles of volcanic origin, like ash.”

Volcanologists and metereologists use this model to re-enact past events and, above all, to make predictions. More specifically it predicts the amount of aerosols in the ground and their concentration in the air. It is therefore of “special interest” to civil aviation. The final objective is to make this type of prediction so as to be prepared during the next volcanic eruption.

Earth from space: A gush of volcanic gas

This image shows the huge plume of sulphur dioxide that spewed from Chile's Puyehue-Cordón Caulle Volcanic Complex, which lies in the Andes about 600 km south of Santiago. It was generated on June 6 using data from the Infrared Atmospheric Sounding Interferometer on the MetOp-A satellite and represents sulfur dioxide concentrations within the full vertical column of atmosphere. As the eruption continued, the image shows how strong winds initially swept the broad plume of sulfur dioxide northwards and then eastwards across Argentina and out over the southern Atlantic Ocean. 
The MetOp program was jointly established by ESA and Eumetsat and forms the space segment of Eumetsat's Polar System. -  Université Libre de Bruxelles (ULB)
This image shows the huge plume of sulphur dioxide that spewed from Chile’s Puyehue-Cordón Caulle Volcanic Complex, which lies in the Andes about 600 km south of Santiago. It was generated on June 6 using data from the Infrared Atmospheric Sounding Interferometer on the MetOp-A satellite and represents sulfur dioxide concentrations within the full vertical column of atmosphere. As the eruption continued, the image shows how strong winds initially swept the broad plume of sulfur dioxide northwards and then eastwards across Argentina and out over the southern Atlantic Ocean.
The MetOp program was jointly established by ESA and Eumetsat and forms the space segment of Eumetsat’s Polar System. – Université Libre de Bruxelles (ULB)

This image shows the huge plume of sulphur dioxide that spewed from Chile’s Puyehue-Cordón Caulle Volcanic Complex, which lies in the Andes about 600 km south of Santiago.

After lying dormant for more than 50 years, a series of rumbling earthquakes signalled the beginnings of this major volcanic eruption. On 4 June, a fissure opened, sending a towering plume of volcanic ash and gas over 10 km high.
Several thousand people were evacuated as a thick layer of ash and pumice fell and blanketed a wide area. Airports in Chile and Argentina were closed as a result.

The image was generated on 6 June using data from the Infrared Atmospheric Sounding Interferometer on Eumetsat’s MetOp-A satellite. As the eruption continued, the image shows how strong winds initially swept the broad plume of sulphur dioxide northwards and then eastwards across Argentina and out over the southern Atlantic Ocean.

Strong westerly winds are common in this region because it lies within the belt of the ‘Roaring Forties’. Since there is little land south of 40º, higher wind speeds can develop than at the same latitudes in the Northern Hemisphere.

Interestingly, over the South Atlantic, the plume take a sharp turn to the north as a pressure system causes the wind to change direction.

The Puyehue-Cordón Caulle complex is a chain of volcanoes that includes the Puyehue volcano, the Cordilera Nevada caldera and the Cordón Caulle rift zone. This event appears to have stemmed from the rift zone and is the most serious since the eruption of 1960, also from the same vent.

Chile has more than 3000 volcanoes, of which around 80 are currently active.

The image represents sulphur dioxide concentrations within the full vertical column of atmosphere. It was generated using data from the interferometer, which was developed by the French space agency CNES for MetOp-A.

Researchers Uncover ‘Stirring’ Secrets of Deadly Supervolcanoes


Researchers from The University of British Columbia and McGill University have simulated in the lab the process that can turn ordinary volcanic eruptions into so-called “supervolcanoes.”



The study was conducted by Ben Kennedy and Mark Jellinek of UBC’s Dept. of Earth and Ocean Sciences, and John Stix of McGill’s Dept. of Earth and Planetary Sciences. Their results are published this week in the journal Nature Geoscience.



Supervolcanoes are orders of magnitude greater than any volcanic eruption in historic times. They are capable of causing long-lasting change to weather, threatening the extinction of species, and covering huge areas with lava and ash.



Using volcanic models made of Plexiglas filled with corn syrup, the researchers simulated how magma in a volcano’s magma chamber might behave if the roof of the chamber caved in during an eruption.


“The magma was being stirred by the roof falling into the magma chamber,” says Stix. “This causes lots of complicated flow effects that are unique to a supervolcano eruption.”



“There is currently no way to predict a supervolcano eruption,” says Kennedy, a post-doctoral fellow at UBC and lead author on the paper. “But this new information explains for the first time what happens inside a magma chamber as the roof caves in, and provides insights that could be useful when making hazard maps of such an eruption.”



The eruption of Mount Tambora in Indonesia in 1815 – the only known supervolcano eruption in modern history – was 10 times more powerful than Krakatoa and more than 100 times more powerful than Vesuvius or Mount St. Helens. It caused more than 100,000 deaths in Indonesia alone, and blew a column of ash about 70 kilometres into the atmosphere. The resulting disruptions of the planet’s climate led 1816 to be christened “the year without summer.”



“And this was a small supervolcano,” says Stix. “A really big one could create the equivalent of a global nuclear winter. There would be devastation for many hundreds of kilometres near the eruption and there would be would be global crop failures because of the ash falling from the sky, and even more important, because of the rapid cooling of the climate.”



There are potential supervolcano sites all over the world, most famously under Yellowstone National Park in Wyoming, the setting of the 2005 BBC / Discovery Channel docudrama Supervolcano, which imagined an almost-total collapse of the world economy following an eruption.

10 questions shaping 21st-century earth science identified


Ten questions driving the geological and planetary sciences were identified today in a new report by the National Research Council. Aimed at reflecting the major scientific issues facing earth science at the start of the 21st century, the questions represent where the field stands, how it arrived at this point, and where it may be headed.



“With all the advancements over the last 20 years, we can now get a better picture of Earth by looking at it from micro- to macro-perspectives, such as discerning individual atoms in minerals or watching continents drift and mountains grow,” said Donald J. DePaolo, professor of geochemistry at the University of California at Berkeley and chair of the committee that wrote the report. “To keep the field moving forward, we have to look to the past and ask deeper fundamental questions, about the origins of the Earth and life, the structure and dynamics of planets, and the connections between life and climate, for example.”



The report was requested by the U.S. Department of Energy, National Science Foundation, U.S. Geological Survey, and NASA. The committee selected the question topics, without regard to agency-specific issues, and covered a variety of spatial scales — subatomic to planetary — and temporal scales — from the past to the present and beyond.



The committee canvassed the geological community and deliberated at length to arrive at 10 questions. Some of the questions present challenges that scientists may not understand for decades, if ever, while others are more tractable, and significant progress could be made in a matter of years, the report says. The committee did not prioritize the 10 questions — listed with associated illustrative issues below — nor did it recommend specific measures for implementing them.


HOW DID EARTH AND OTHER PLANETS FORM?



While scientists generally agree that this solar system’s sun and planets came from the same nebular cloud, they do not know enough about how Earth obtained its chemical composition to understand its evolution or why the other planets are different from one other. Although credible models of planet formation now exist, further measurements of solar system bodies and extrasolar objects could offer insight to the origin of Earth and the solar system.

WHAT HAPPENED DURING EARTH’S “DARK AGE” (THE FIRST 500 MILLION YEARS)?



Scientists believe that another planet collided with Earth during the latter stages of its formation, creating debris that became the moon and causing Earth to melt down to its core. This period is critical to understanding planetary evolution, especially how the Earth developed its atmosphere and oceans, but scientists have little information because few rocks from this age are preserved.


HOW DID LIFE BEGIN?



The origin of life is one of the most intriguing, difficult, and enduring questions in science. The only remaining evidence of where, when, and in what form life first appeared springs from geological investigations of rocks and minerals. To help answer the question, scientists are also turning toward Mars, where the sedimentary record of early planetary history predates the oldest Earth rocks, and other star systems with planets.


HOW DOES EARTH’S INTERIOR WORK, AND HOW DOES IT AFFECT THE SURFACE?



Scientists know that the mantle and core are in constant convective motion. Core convection produces Earth’s magnetic field, which may influence surface conditions, and mantle convection causes volcanism, seafloor generation, and mountain building. However, scientists can neither precisely describe these motions, nor calculate how they were different in the past, hindering scientific understanding of the past and prediction of Earth’s future surface environment.


WHY DOES EARTH HAVE PLATE TECTONICS AND CONTINENTS?



Although plate tectonic theory is well established, scientists wonder why Earth has plate tectonics and how closely it is related to other aspects of Earth, such as the abundance of water and the existence of the continents, oceans, and life. Moreover, scientists still do not know when continents first formed, how they remained preserved for billions of years, or how they are likely to evolve in the future. These are especially important questions as weathering of the continental crust plays a role in regulating Earth’s climate.


HOW ARE EARTH PROCESSES CONTROLLED BY MATERIAL PROPERTIES?



Scientists now recognize that macroscale behaviors, such as plate tectonics and mantle convection, arise from the microscale properties of Earth materials, including the smallest details of their atomic structures. Understanding materials at this microscale is essential to comprehending Earth’s history and making reasonable predictions about how planetary processes may change in the future.


WHAT CAUSES CLIMATE TO CHANGE — AND HOW MUCH CAN IT CHANGE?



Earth’s surface temperature has remained within a relatively narrow range for most of the last 4 billion years, but how does it stay well-regulated in the long run, even though it can change so abruptly” Study of Earth’s climate extremes through history — when climate was extremely cold or hot or changed quickly — may lead to improved climate models that could enable scientists to predict the magnitude and consequences of climate change.


HOW HAS LIFE SHAPED EARTH — AND HOW HAS EARTH SHAPED LIFE?



The exact ways in which geology and biology influence each other are still elusive. Scientists are interested in life’s role in oxygenating the atmosphere and reshaping the surface through weathering and erosion. They also seek to understand how geological events caused mass extinctions and influenced the course of evolution.


CAN EARTHQUAKES, VOLCANIC ERUPTIONS, AND THEIR CONSEQUENCES BE PREDICTED?



Progress has been made in estimating the probability of future earthquakes, but scientists may never be able to predict the exact time and place an earthquake will strike. Nevertheless, they continue to decipher how fault ruptures start and stop and how much shaking can be expected near large earthquakes. For volcanic eruptions, geologists are moving toward predictive capabilities, but face the challenge of developing a clear picture of the movement of magma, from its sources in the upper mantle, through Earth’s crust, to the surface where it erupts.



HOW DO FLUID FLOW AND TRANSPORT AFFECT THE HUMAN ENVIRONMENT?




Good management of natural resources and the environment requires knowledge of the behavior of fluids, both below ground and at the surface, and scientists ultimately want to produce mathematical models that can predict the performance of these natural systems. Yet, it remains difficult to determine how subsurface fluids are distributed in heterogeneous rock and soil formations, how fast they flow, how effectively they transport dissolved and suspended materials, and how they are affected by chemical and thermal exchange with the host formations.