Subglacial eruption

Subglacial eruptions, those of ice-covered volcanoes, result in the interaction of magma with ice and snow, leading to meltwater formation, jökulhlaups, and lahars. Flooding associated with meltwater is a significant hazard in some volcanic areas, including Iceland, Alaska, and parts of the Andes. Jökulhlaups (glacial outburst floods) have been identified as the most frequently occurring volcanic hazard in Iceland, with major events where peak discharges of meltwater can reach 10,000 – 100,000 m3/s occurring when there are large eruptions beneath glaciers. It is important to explore volcano-ice interactions to improve the effectiveness of monitoring these events and to undertake hazard assessments. This is particularly relevant given that subglacial eruptions have demonstrated their ability to cause widespread impact, with the ash cloud associated with Iceland's Eyjafjallajökull eruption in 2010 resulting in significant impacts to aviation across Europe. Given that subglacial eruptions occur in often sparsely populated regions, they are not commonly observed or monitored; thus timings and sequences of events for an eruption of this type are poorly constrained. Research of the 1969 Deception Island eruption demonstrates that the impact of a subglacial eruption is not limited purely by glacier thickness, but that the pre-volcanic ice structure and densification (proportion of impermeable ice) play a role as well. In this case, even though the glacier was thin, a large jökulhlaup was observed as the glacier was largely made up of impermeable (unfractured) ice with a sudden supraglacial flood once the cavity has reached capacity. The resulting flood severely damaged buildings on the island, with complete destruction of a British scientific station. Over a period of 13 days in 1996, 3 km2 of ice was melted with erupted magma fracturing into glass to form a 7 km long and 300 m high hyaloclastite ridge under 750 m of ice at Gjalp fissure vent of Grímsvötn volcano in Iceland.

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Related concepts (3)

Subglacial eruption

Types of volcanic eruptions

Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs, and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed. Some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series.

Lava

Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or underwater, usually at temperatures from . The volcanic rock resulting from subsequent cooling is also often called lava. A lava flow is an outpouring of lava during an effusive eruption. (An explosive eruption, by contrast, produces a mixture of volcanic ash and other fragments called tephra, not lava flows.