Aftermath of a Jökulhlaup
This photo shows the remains of a steel highway bridge, destroyed by the catastrophic 1996 jökulhlaup.
A jökulhlaup is a glacial outburst flood that occurs when a volcanic eruption under a glacier causes countless tons of ice to melt - but remain trapped under the ice cap. Eventually the heat of the steam causes the entire ice cap to rise up, and the melted water rushes out destroying everything in its path.
The 1996 jökulhlaup caused by an eruption of Grímsvötn released water at a rate of 50,000 cubic meters/second.
Scientists believe that 8-10,000 years ago, a single catastrophic jökulhlaup carved this gorge through which the Jökulsá á Fjöllum river flows. The gorge runs from Vatnajökull all the way to the Greenland Sea.
This waterfall, Selfoss, is just a couple of hundred meters upstream of Dettifoss, the most powerful waterfall in Europe (flow approx 193 cubic meters/second).
Powerful as Dettifoss and Selfoss are, they are faint echoes of the jökulhlaup that created them.
The Danger Zone
One of Iceland's most dangerous volcanoes is Katla (4 eruptions since 1947). When Katla erupts, the resulting jökulhlaup starts here - at Emstrur. The Emstrur huts, where we stayed, are located at the mouth of an amazing gorge carved through the volcanic rock by jökulhlaups. When volcanic activity is detected at Katla, the wardens begin shooting off flares and sounding alarms (sirens and flash-bangs).
When you hear those alarms, you get to high ground as fast as you can - no delay.
The Emstrur Gorge
Carved by centuries of jökulhlaups, the Emstrur Gorge is an amazing place. To get an idea of the scale of this gorge, look for the SUV parked on the top left rim of the gorge.