Gluggafoss

Take Highway 1 to the town of Hvolsvöllur then turn north onto Route 261 and follow it for 17.3km to where the road crosses the Merkjá below the falls, and a sign points to the parking area to the left (north). Alternatively, take Route 250, just west of Seljelandsfoss, north from Highway 1 for 12km, then turn left at the T-junction where it intersects Route 261. The falls will be visible from this point. A short trail leads from the parking area up a set of steps to a viewing area at the base of the upper tier for a closer look.Gluggafoss is a moderate to low volume, but very unique waterfall found along the Merkjá where it makes its final descent to the flood plain of the Markarfljót, just northwest of the volcano Eyjafjallajökull. The falls drop in two steps, first plunging 146 feet into a narrow recess, and then shortly after spreading out over a broader ledge and falling in several channels for 28 feet. What makes the falls so unique is the upper tier drops over a ledge formed by stratified Tuff (basically heavily compacted ash, sand, and boulders) which is easily eroded. In plunging down the cliff, the stream has cut down the bedrock in such a way that there are presently three natural arches spanning the face of the falls. The first is situated near the top of the falls and is difficult to see well from its base. The other two are found one on top of the other near the base of the upper tier. During periods of heavier flow, part of the falling water actually impacts on the second and third arches and sprays outward while the rest plunges into the grotto before pouring out from beneath the third arch. According to the signboard at the falls, before 1947 the upper half of the falls was not visible at all because of how it had eroded back into the grotto, and the only portion of the falls that could be seen was what was visible between the arches - the "windows" which give the falls its name. However following the eruption of the volcano Hekla in 1947, over 20cm (almost 8 inches) of Ash was deposited in the drainage above the falls, all of which washed downstream and clogged the tunnel where the falls was once hidden, thus forcing it to bypass the arches entirely. It allegedly took the stream nearly 50 years to erode away all the debris which was deposited by the eruption and return to (nearly) its previous form. Given this history, there is a good chance that another catastrophic flood in the drainage may severely alter the falls further.The falls have been referred to as Merkjárfoss at times, but the name Gluggafoss is established on site. Glugga is Icelandic for Window (referring to the windows in the bedrock where the falls can be seen as they pass behind the arches).