South Iceland’s landscape is defined by a meeting of rivers, cliffs and volcanic activity, but few places bring these elements together as distinctly as Gluggafoss. Standing in Fljótshlíð, an area shaped by natural forces both gentle and violent, Gluggafoss (pronounced [ˈklʏkːaˌfɔsː]) is the most prominent in a scenic row of falls on the river Merkjá.
Gluggafoss is also called Merkjárfoss, both names are acknowledged at the site, hinting at the waterfall’s strong relationship with the river that forms it. The falls are about 17 kilometres from Hvolsvöllur, the nearest town, and can be found just off Route 261 on Iceland’s southern plains.
Layers of rock, tunnels of water
Gluggafoss drops a total of about 52 metres in two distinct leaps: first 44 metres into a close recess in the cliff, then another 8.5 metres divided between three channels. What makes Gluggafoss especially curious is not just its height or dual structure, but the cliff behind it. The upper section of the cliff is made of palagonite, also called tuff rock, a volcanic material softer than the harder basalt beneath.
Over time, the constant flow of the Merkjá has bored holes and tunnels through this upper, softer layer. These are called ‘gluggar’ in Icelandic, which means ‘windows’. Standing at the foot of Gluggafoss, one can look up and notice these gluggar: the river, at certain angles, is partly seen through them, producing the impression of water vanishing behind stone and then reappearing. These natural tunnels and holes are a rare geological feature even in Iceland’s catalogue of unusual waterfalls.
A waterfall reshaped by eruption
The appearance of Gluggafoss has not remained constant. Hekla, a volcano some 30 kilometres to the north-northeast, erupted in 1947. The event sent ash into the river Merkjá and the fumaroles of Gluggafoss. For decades after, volcanic material so thoroughly filled the tunnels that only limited parts of the upper waterfall were visible, usually through three vertically stacked windows.
Only with the passage of time and the steady hand of erosion did the river clear its course again, reopening the hidden windows and restoring the waterfall’s full effect. Today the contrast of volcanic tuff and basalt remains exposed, bearing witness to centuries of interaction between fire, water and stone.
Sources
- Wikipedia
- Wikipedia (Icelandic) in Icelandic
