Volcanic eruption in Eyjafjallajökull in South Iceland
Fire and ice
Glacier ice and volcanoes, something amazing but they do not mix so well together. Iceland one of few places on Earth where you have glaciers and active volcanoes at the same place. In Iceland, we have a plump or a hot spot located underneath the Vatnajökull glacier. Where there is a lot of magma rather close to the ground.
There are about 36 active volcanoes in Iceland and many of them are covered with glacier ice. The best known are probably:
Jökulhlaup (glacial outbursts)
When we know there is a volcanic eruption starting underneath a glacier we can expect a lot of glacier ice being melted in a short period of time. Meaning there will be a lot of water trapped inside the glacier where the volcanic eruption is taking place.
This will, in the end, cause a jökulhlaup (glacial outburst) where the water breaks outside from underneath the glacier usually going the easiest way out from underneath some of the outlet glaciers. Like when we have a glacier outburst after a volcanic eruption in Katla it usually comes out from underneath Kötlujökull glacier on Mýrdalssandur black lava sand area east of Vík.
If there will be a volcanic eruption in Grímsvötn the jökulhlaup (glacier outburst) usually comes from underneath the Skeiðarárjökull glacier near Skaftafell.
Öræfajökull, Katla, Grímsvötn, and Gjálp
These events can happen only a few hours after the volcanic eruption starts, like with Öræfajökull, it can expect to happen within an hour from the beginning of the eruption. With the volcano Katla the time factor can be a couple of hours, and with Grímsvötn and Gjálp it can be a couple of days until the glacial outburst happened. All depending on where in the glacier the volcanic eruption takes place and how thick the ice cap is there.
It also depends how big these glacier outbursts are how much glacier ice was melted during the beginning of the eruption.
It is believed that the biggest jökulhlaup (glacier outbursts) have been up to 500.000 m3/sec. during a volcanic eruption in volcano Katla for the past thousands of years.
It is estimated that the glacial outburst in the Gjálp volcanic eruption in 1996 was around 50 m3/sec.
Now the focus is on the glacier and volcano Öræfajökull in Iceland. After a long sleep, the volcano Öræfajökull has woken up. Showing some activity underneath, with earthquakes and increase in geothermal heat, forming a small depression in the crater on the top of the volcano.
Here in Iceland, we have learned through history where to live and not to live. At the beginning of the settlement, the Vikings came here without any knowledge about volcanoes and what they were capable of. Which caused some casualties in the first centuries for people living in Iceland.