After a brief stop in Skaftafell, we will make a short stop here by the monument of the longest bridge built in Iceland. Think about the changes in the landscape over the years and the forces of nature.

A complex river system runs through the area, coming from two main systems, which are the Núpsvötn-Súla-Gígjukvísl systems emerging from the western side of Skeiðarárjökull, and the Skeiðará system, which emerges from the eastern side. These rivers carry large quantities of debris onto the sandur plains on a day-to-day basis, but when jökulhlaups occur at regular intervals, they are catastrophic. The jökulhlaups at Skeiðarársandur originate in two ways. Drainage of the caldera at lake Grímsvötn, and by sudden drainage of the ice-dammed marginal Lake Grænalón. 

On a regular basis there are jökulhlaups with a total volume of 1-3 km3, and a maximum discharge of 5000-10.000 m3/s. Unfortunately, this normal flood pattern is sometimes interrupted by volcanic activity, including jökulhlaups, like the one generated by the subglacial eruption at Gjálp in 1996. When this happens, large quantities of ice melt quickly discharge the melt-water directly into the Grímsvötn caldera, resulting in a rapid rise of the water level. This causes catastrophic jökulhlaups bursting through the outlets of Skeiðará, Súla and Gígjukvísl. Those typically dump large volumes of debris, and leaves gigantic blocks of glacier ice on the sandur plain. Water covers the whole area.

In this flood, some bridges were ruined, others damaged. The bridge over Skeiðará, was for years the longest bridge in Iceland, completing the ring road around Iceland. As a 10 year old girl, I happened to be present when it was formally opened in 1974. I clearly remember the celebration and how big of accomplishment this was for my relatives living in Hornafjörður, but also how scary the dark brown roaring water in the river was.

Today we have this new, much shorter bridge over Skeiðará.