To experience a volcanic eruption is to witness the sheer force of nature. If you want to see one for yourself, Iceland is a great location. Since 2021, there have been seven eruptions on the Reykjanes Peninsula, near Reykjavík.
These recent eruptions in Iceland have caught the attention of geoscientists like me. The eruptions are helping us understand in incredible detail how volcanoes work. My team has been sampling the erupting lava from the Reykjanes Peninsula and has found some interesting results.
One of our findings suggests that magma from the first eruption collected just below the island’s surface, where it built up the energy to erupt spectacularly. This first burst of volcanism made it easier for more eruptions to follow.
Why is Iceland called the land of fire?
The island nation of Iceland is sometimes called “the land of ice and fire.” Early settlers witnessed several large “fires” – or volcanic eruptions – along the Reykjanes Peninsula.
After about 800 years without a volcanic eruption on the Reykjanes Peninsula, the Fagradalsfjall volcano erupted on March 19, 2021. Two more separate volcanic eruptions have since occurred at Fagradalsfjall in 2022 and 2023. Four more eruptions have then occurred west of the Sundhnúkur fissure system in 2023 and 2024.
While these eruptions are an incredible sight to behold, they also have the power to wreak havoc. The recent Sundhnúkur eruptions threatened the fishing village of Grindavík, the geothermal power plant at Svartsengi, and Iceland’s number one tourist destination, the Blue Lagoon geothermal spa. Lava erupted within the city limits of Grindavík, and only man-made berms prevented further destruction.
What makes Iceland so volcanically active?
Iceland is a unique place on Earth. It is part of a huge chain of volcanoes that are submerged in the middle of the Atlantic Ocean, with Iceland rising above the ocean surface. This volcanic chain is known as the Mid-Atlantic Ridge and plays a vital role in plate tectonics.
Plate tectonics describes how the enormous, rigid plates that make up the Earth’s crust slide past, into, and under each other. Their behavior slowly changes the Earth’s surface. In some places, the plates collide, forming mountain ranges like the Himalayas. In other places, one plate slides under the other, creating volcanoes and earthquakes, as in Japan.
At the Mid-Atlantic Ridge – which stretches between the South Atlantic Ocean and the Arctic Ocean – the plates are pulling apart, allowing molten magma to flow through. This magma solidifies into volcanic crust, creating new parts of the tectonic plates.
Geologists have also found a buoyant, hot plume of rocky material rising from deep within the Earth and crossing the Mid-Atlantic Ridge beneath Iceland. This plume, along with several other similar plumes in the central and southern Atlantic Ocean, may have caused the formation of the Atlantic Ocean Basin more than 200 million years ago.
The plate tectonics of the Mid-Atlantic Ridge and the hot, rocky plume beneath Iceland together form Iceland’s volcanoes.
Scientists have been able to show that past eruptions on the Reykjanes Peninsula are not random in time or space. Instead, they occur in periods that last centuries and along the same volcanic zones. These patterns indicate that these volcanic episodes occur when enormous tectonic forces are pulling the Reykjanes Peninsula apart. It appears that while the plates are pulling apart at a steady rate, volcanism along the Reykjanes Ridge segment pulses with time.
What causes the eruption?
Many groups, including my colleagues from Iceland, collect the erupted lavas almost daily. The collected samples provide a vital scientific time series of the eruptions.
Taking a volcanic time series is like taking blood samples from someone regularly to understand their medical condition. In this case, the blood is red-hot lava.
An initial study by a different team in 2022 suggested that the mantle – the solid geological layer beneath the Earth’s crust – melted to feed the lava in Iceland, and that the chemical composition of the lava changed over time. They suggested that these changes had to do with where and when the melting occurred in the mantle.
In July 2024, my research team and I published a longer time series of the lava from the eruption, using a sensitive chemical method that provided more insight into the composition and origin of the lava.
The basalt layer on which people in Iceland live extends to a depth of about 15 kilometers. It is part of the Earth’s crust. The mantle that lies directly beneath this crust is clear: it is composed mainly of minerals such as olivine that form a rock called peridotite. The magmas that feed these volcanic eruptions come from mantle peridotite.
The chemical method my team used revealed that the initial magmas that fueled these eruptions rose from the mantle but remained suspended in a magma chamber below the surface for a year. The rocks in the chamber walls melted into the magma, and we could see traces of it in our analyses.
Our research also suggests that the magmas got water, carbon dioxide and other gases from sitting in the magma chamber. This water and gas allowed the magma to build up enough pressure to break through the surface and erupt as lava.
Magma accumulating in the Earth’s crust can cause explosive eruptions. The onset of eruptions like those in Iceland or La Palma in the Canary Islands in 2021 may require this type of accumulation.
What can we expect in the future?
History tells researchers that these eruptions will likely last a long time. The volcanoes will erupt periodically every few years, for days to months at a time, for hundreds of years into the future.
Generations of geologists and volcanologists will likely build their careers in Iceland, and millions of geotourists will be able to experience the enchantingly beautiful eruptions.
With all these eruptions, Icelanders will have to adapt. Lava flows can disrupt infrastructure such as the Svartsengi geothermal plant, and volcanic gases can cause health problems.
The eruptions of Fagradalsfjall and Sundhnúkur have already given scientists a wealth of data and insight into how volcanoes work. Ongoing research into volcanism on the Reykjanes Peninsula will help scientists understand how, when and why eruptions occur, and better manage the hazards that come with living with volcanoes.
This article is republished from The Conversation, a nonprofit, independent news organization that brings you facts and reliable analysis to help you understand our complex world. It was written by: James Day, University of California, San Diego
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James Day receives funding from the US National Science Foundation.