Litli-Hrútur eruption seen from space

Litli-Hrútur, which translates to ‘Little Ram,’ is part of the Fagradalsfjall volcanic area in southwest Iceland. After around 800 years of silence, the volcanic area burst into life in March 2021 with an eruption in the Geldingadalur valley followed by a smaller eruption in the nearby Meradalur valley in August 2022.

Almost one year later, a new eruption began at Litli-Hrútur mountain. In the week leading up to the eruption, thousands of small earthquakes had been recorded in the area, the largest of which was a magnitude 4.8 quake, according to the Icelandic Met Office.

And, as of today, the eruption is still ongoing. Tourists and spectators are flocking to the site, mesmerised by the ongoing volcanic activity and eager to witness the natural spectacle up close. For those unable to make the journey, the eruption can still be experienced from the comfort of their homes through a dedicated livestream as well as satellite imagery.

Satellite technologies now make it possible to monitor volcanic activity in even the most isolated corners of the globe. Satellites carry different instruments that provide a wealth of complementary information to better understand volcanic eruptions. Optical satellites, such as the Copernicus Sentinel-2 mission, can image smoke plumes, lava flows, mudslides and ground fissures.

The image above, captured by Sentinel-2, shows the smoke plume coming from the Litli-Hrútur volcano on 11 July and shows the plume blowing in a southwest direction. Sentinel-2 is based on a constellation of two identical satellites, each carrying an innovative wide swath high-resolution multispectral imager with 13 spectral bands.

Although the site of the new eruption is a popular tourist destination, it is also potentially hazardous. New fissures could open without warning, rivers of lava can spew unexpectedly and toxic gas, including sulphur dioxide, can quickly fill the air. Sulphur dioxide can be harmful health, especially when present in high concentrations in the air.

Sulphur dioxide has a relatively short lifespan due to various chemical reactions that remove it from the air. It can be oxidized to form sulphate aerosols or dissolved in water to create sulphuric acid, which then gets washed out by precipitation.

However, when sulphur dioxide is transported into the stratosphere, its behaviour changes. In the stratosphere, at higher altitudes, there is less atmospheric mixing, and chemical reactions are less frequent. As a result, sulphur dioxide can persist for longer periods, ranging from weeks to months or even years.

Atmospheric sensors on satellites can identify the gases and aerosols released by the eruption, as well as quantify their wider environmental impact. The animation above shows the sulphur dioxide concentrations from the eruption from 11-13 July 2023, captured using data from the Copernicus Sentinel-5P.

Sulphur dioxide concentrations across the globe can be monitored using the Copernicus Sentinel-5P Volcanic Sulphur Dioxide online platform. Using data from Sentinel-5P, the platform shows the daily sulphur dioxide concentrations coming primarily from volcanic sources.