Long Eruption on Reykjanes Could Form Shield Volcano Skip to content

Long Eruption on Reykjanes Could Form Shield Volcano

By Yelena

People admiring the Reykjanes peninsula eruption from the edge of the flowing lava
Photo: Golli. People admiring the Reykjanes peninsula eruption from the edge of the flowing lava.

There is no way to tell how long the ongoing eruption on Iceland’s Reykjanes peninsula will last, experts say. Yet if it continues, the slow-flowing, highly fluid lava could potentially form a shield volcano, like Hawaii’s Mauna Loa, often cited as the largest volcano on earth.

The Geldingadalur eruption has now been ongoing for nine days with a steady rate of flow between 5-7 cubic metres per second, according to the Icelandic Met Office. The lava flow is filling Geldingadalur valley, where the erupting fissure is located. “If the eruption keeps at a similar rate, it is modelled that the lava will flow east towards Merardalur valley,” a tweet from the Met Office states. “If the volcano continues to erupt it could end up being categorised as a shield volcano.”

Shield volcanoes are gently-sloping, often large volcanoes, usually formed over long periods of time. The lava fields from such volcanoes can extend several kilometres around their source. The lava emitted by the Geldingadalur eruption is highly fluid – this means it travels further and forms thinner layers than more viscous lava. Over time, such layers can form the gently-rounded shape of a shield volcano, thus named due to its resemblance to a warrior’s shield lying on the ground. These types of volcanoes are more commonly formed at continental rifts such as the one cutting across the Reykjanes peninsula. Iceland does have other shield volcanoes, including Skjaldbreiður (1,060m, whose name is roughly translated as “broad shield”) and Trölladyngja (1,468m), the country’s biggest volcano of that sort. Most of Iceland’s shield volcanoes were formed thousands of years ago.

While experts cannot say how long the Geldingadalur eruption will last or whether it will in fact form a shield volcano, the lava’s deep source and slow but steady flow indicate a long eruption could be ahead.

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