Monitoring Gas Emissions from Volcanoes to Predict Volcanic Activity

To understand and predict the behaviour of volcanoes an increasing number of scientists are combining geological monitoring and geochemical models. By measuring and monitoring the prevalence of gases like CO2, scientists hope to be able to better predict the likelihood of volcanic eruptions.

In 2010 Iceland’s Eyjafjallajökull volcano erupted, releasing 250 million cubic metres of ash into the atmosphere. The eruption disrupted 100,000 flights and 10 million journeys, bringing the global aviation industry to a standstill and costing hundreds of millions of dollars. [1]

In the past predicting when one of the world’s 1,500 volcanoes is about to erupt has been based on monitoring and measuring the seismic activity around the site. However, since the 1970s correlation spectrometers have been used to measure the levels of sulfur dioxide in the volcanic plume as scientists began to understand that higher levels of gas emission from a volcanic site indicates a higher chance of eruption.

In more recent times, using geochemical models, a growing body of research and evidence shows measuring the levels of emitted CO2 can be used to predict the risk of an eruption.

Carbon Dioxide Gas Monitoring to Predict Volcanic Activity

Sitting to the north of Sicily, Italy’s Mount Stromboli has erupted almost continuously for over 2,000 years. [2] This volatile island is the perfect environment for volcanologists to test their theories, confident that they won’t need to wait too long for an eruption.

When magma begins to rise to the surface its pressure decreases, releasing gases into the environment. This process, known as degassing, [4] releases volatiles into the air, including water (H2O), carbon dioxide (CO2) sulphur dioxide (SO2) and hydrogen sulphide (H2S).

These gases escape through fumaroles, appearing as plumes of smoke. Scientists have discovered that by studying the composition of this gaseous mixture and monitoring fluctuations in their composition, they may be better able to predict the likelihood of volcanic eruption.

Between 2007 and 2012 Italian scientists at the Stomboli Volcano [3] used fixed cameras, a Multi-GAS analyser (to monitor SO2 and CO2 fluxes) and continual fumerole temperature recording to monitor geological and geochemical variations at the site.

An Edinburgh Sensors’ Gascard NG gas sensor was used, within the Multi-Component Gas Analyser System (Multi-GAS), to calculate the CO2 concentrations within the volcanic flume. Located 2m inside the volcanic fracture, the automated instruments provided CO2 recordings within a measurement range of 0-3000 ppm; at an impressive accuracy range of ±2 % and a resolution of 0.1 ppm.

The Multi-GAS system allowed researchers to map the long-term CO2 trends at the volcano, establishing a mean value, and recording variations. When considered with all other data collected at the site, analysis shows correlation between CO2 spikes and volcanic activity.

Monitoring of the degassing activity can also help scientists gain an insight into the ‘plumbing system’ within a volcano. Beneath the surface, the variations in the structure of the earth, the storage of magma and its periodic recharging (as fresh magma is introduced) are all important processes which are important to monitor. CO2 monitoring enables researchers to define and then spot and track ‘signature’ styles of degassing in order to determine what is happening underground.

Measuring Dissolved Carbon Dioxide in Volcanic Aquifers

Not all of the gases emitted during the degassing process make it to the surface. Some can condense or dissolve into fluids in groundwater, creating hydrothermal aquifers, the constitution of which are of increasing interest to researchers.

While measurements of carbonic acid (formed as CO₂ rises to the surface and comes into contact with water) and water PH can provide indications on the level of CO₂, a group of Italian researchers chose to create an automated monitoring system using an infrared spectrometer based on the principles of Henry’s Law. [4]

Measuring the dissolved CO₂ in natural waters around the Stromboli earthquake, this automated system has allowed researchers to establish what they describe as a “clear correlation between the changes in PCO₂ in the thermal aquifer and the changes in volcanic activity”

After defining a baseline, researchers were able to monitor the PCO₂ levels around the Stromboli Volcano. Monitoring the daily averages of PCO from January 2009 to May 2012, researchers were able to identify correlations within the data, relating increased CO₂ concentrations to volcanic activity.

Combining Gas Sensors with a UAV for Extreme Measurements

Collecting accurate data on volcanoes can be dangerous, with crater temperatures reaching extreme levels. In tackling this problem, scientists at the University of Costa Rica [5] are using UAVs (drones) fitted with miniature gas spectrometers to provide accurate measurements of the compounds within the gas plumes above volcanoes.

Flying on a pre-determined course, the VW-100’s 10 megapixel camera allows human on the ground to view the progress of drone as it enters into inhospitable areas to collect essential measurements. This drone-sensor array has the ability ability to enter volcanic plumes and provide accurate, real-time measurements.

The Gascard NG

At the heart of Edinburgh Sensors’ Gascard NG is its proprietary NDIR technology that enables the unit provide real-time measurement of CO₂ from levels as low as 0-500ppm to 0- 3%. This low maintenance, high-quality sensor is perfect for the accurate scientific measurements demanded by volcanologists.

Once the data has been collected, true RS232 communications, and optional on board LANsupport, mean the data is easily accessible and shared from the unit. The unit’s firmware can support a 4 segment LCD or modern graphical display if required.

The Gascard NG has been designed to be integrated within OEM applications, interoperating seamlessly with other technologies, like the Multi-GAS system used in Italy.

Designed for field applications and built to exacting standards, the unit offers a perfect low-maintenance solution. It is designed to perform in the most inhospitable of environments, due to its extensive temperature compensation and on-board barometric pressure correction, that has been tested and proven in performance.

References

1. EUROCONTROL – Report on the 2010 Ash Clouds Impact on Air Traffic
2. Volcano Report on Stromboli Activity
3. S. Inguaggiato et al., Development of an Automated Monitoring System and First Application to the Stromboli Volcano, Annals of Geophysics, 54, 2011
4. S. Calvari et al., Major Eruptive Style Changes Induced by Structural Modifications of a Shallow Conduit System, Bull Volcano, 76, 2014
5. Tico Times – Unmanned Drones to Explore Mystery of Volcano Plumes