Slight Decrease in Eruption Activity

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Eruption

Slight Decrease in Eruption Activity

By Zoë Robert
Holuhraun eruption

Photo: Institute of Earth Sciences.

The eruption in Holuhraun continues, although there appears to have been a slight decrease in activity compared to yesterday. 

The Scientific Advisory Board of the Icelandic Civil Protection Department concluded the following at their midday meeting today:

A noticeable decrease in seismicity has occurred during the last 24 hours. The level of activity is approximately half of that during recent days. Since midnight last night, around 300 earthquakes have occurred. At the same time yesterday, around 500 earthquakes had been detected.

The rate of deformation at GPS sites closest to the dike intrusion has decreased. Together with an overnight decrease in seismicity, this implies that magma inflow appears to match magma outflow at the eruption site.

The eruption has not created any ash fall. A white plume of steam and gas rises from the fissure, reaching an elevation of about 4.5 km (2 miles) above sea level. Downwind, a volcanic cloud extends from the eruption site. Yesterday afternoon a white cloud from the eruption extended 60 km to the north-northeast.

In comparison to yesterday, more sulfur dioxide has been measured in the eruption cloud.

Sandstorms on the floodplain around the eruption site have contributed fine-grained particles to the eruption cloud. This was seen as a light-brown haze earlier today near to Egilsstaðir, East Iceland.

The eruptive fissure is about 1.5 km in length, positioned about 4.5 km from the ice margin of Dyngjujökull glacier.

At 14:00 UTC yesterday, the lava flow was 4.2 km2 in area. At 08:00 UTC the edge had extended 1.5 km to the east-southeast.

The eruption continues, although there appears to have been a slight decrease in activity compared to yesterday.

It remains unclear how the situation will develop. Four scenarios are still considered most likely:

- The migration of magma could stop, resulting in a gradual reduction in seismic activity and no further eruptions.

- The dike could reach the Earth’s surface causing another eruption, possibly in a new fissure. Lava flow and (or) explosive activity cannot be excluded.

- The intrusion reaches the surface and another eruption occurs where either the fissure is partly or entirely beneath Dyngjujökull. This would most likely produce a flood in Jökulsá á Fjöllum and perhaps explosive, ash-producing activity.

- An eruption in Bárðarbunga. The eruption could cause an outburst flood and possibly an explosive, ash-producing activity. In the event of a sub-glacial eruption, it is most likely that flooding would affect Jökulsá á Fjöllum. However it is not possible to exclude the following flood paths: Skjálfandafljót, Kaldakvísl, Skaftá and Grímsvötn.

Other scenarios cannot be excluded.

The Aviation Color Code for Bárðarbunga remains at ‘orange’ and the code for Askja at ‘yellow.’

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