Höhepunkte: 
Nestled between the glaciers Eyjafjallajökull, Mýrdalsjökull, and Tindfjallajökull is Þórsmörk (Thor's Valley), a nature reserve in the southern Icelandic highlands. Þórsmörk is one of Iceland's most popular hiking destinations.
Strictly speaking, Þórsmörk is a valley and a mountain range between the Krossá, Þröngá, and Markarfljót rivers. Locals, however, often use the name "Þórsmörk" when referring to a much larger region that is composed of the area between Þórsmörk proper, and the Eyjafjallajökull glacier volcano.
Landscapes and Geology
Contrasting vistas of lush oases and roaring glacier rivers cutting through black desert expanses not only make Þórsmörk unique to Iceland but to the entire world. Parts of the valley are rich with moss, fern, and Birchwood, while jagged mountain ridges and ice-capped peaks crown the horizon.
The valley's climate is warmer and calmer than usual in south Iceland, which often causes Þórsmörk's mountains to be cloaked in a veil of mist that materialises when the warm valley air ascends and mixes with the descending cold breath of the glaciers above.
Activities
Þórsmörk's surrounding hills, slopes and mountains are beset with small valleys and gullies that make for some of Iceland's most astonishing hiking routes. Experienced hikers, therefore, have a wealth of trails to trek, varying in distances and difficulty. In fact, Þórsmörk offers two of the most popular trails in Iceland, the Fimmvörðuháls and the Laugavegur.
Fimmvörðuháls is a 30km trail that takes you into the hills beneath the Eyjafjallajökull glacier volcano and to the volcanic craters Magni and Móði, which are still steaming from the eruption of 2010. The 55 km Laugavegur path takes you from Þórsmörk to the Landmannalaugar geothermal area which is home to an incredible wealth of hot springs and rhyolite mountains of vibrant colours. A short but demanding hike from Þórsmörk up Mt.Útigönguhöfði is suitable for those who are looking for stunning views and don't mind a little physical challenge.
Accommodation and How to get there
During winter (October 16th - April 30th) the road into Þórsmörk is impassable. In summer (May 1st - October 15th) a special 4x4 mountain bus runs three times per day from the BSÍ bus terminal in central Reykjavík. Once there you have the choice setting up base in a small hut in Húsadalur valley, a private room or a dormitory in Langidalur valley, or to camp in Þórsmörk's campsite. Please note that the huts, private rooms and dormitories must be booked well in advance.
The glacier volcano of Eyjafjallajokull (1651 m) is located at the borders of the South Icelandic highlands. It featured prominently in world news in 2010 when ash from its eruption halted air traffic in Europe.
An ice cap of about 100 km with several outlet glaciers covers the caldera of Eyjafjallajökull that stands at the height of 1651 meters. The diamaeter of its highest crater is around 3-4 km2 wide and the rim has several peaks.
Eyjafjallajokull glacier volcano lies north of Skogar, and to the west of Myrdalsjokull glacier and the massive volcano there; Katla.
Eyjafjallajokull is thought to be related geologically to Katla in Myrdalsjokull and eruptions in the former have often been followed by eruptions in the latter.
The 2010 eruptions
The end of 2010 saw some small seismic activity that gradually increased and resulted in a small eruption in March of 2010, characterized by a flow of alkani-olivine basalt lava.
This first stage lasted until April 12th and created the volcanic craters Magni and Modi at the Fimmvorduhals trail. They are so far Iceland's newest vocanic craters, and still eminate steam with lava glowing under the surface.
However it was the second phase of the eruption that started on April 14th that created the huge ash cloud that rose about 9 km into the skies.
This eruption halted air traffic in Europe for days, and its estimated that as many as 107.000 flights may have been cancelled during the week it lasted.
The ejected tephra measured around 250 million cubic meters. This ash cloud lasted for six days and some more localized disruption continued into May. The eruption was officially declared to be over in October 2010, as the snow on the glacier had ceased to melt.
Future volcanic developments?
Eyjafjallajokull erupted in years 920, 1612 and again 1821-1823.
Its latest eruptions were the two that occurred in 2010.
Future volcanic developments remain unclear. The area is still highly active and can be quite unpredictable. It continues, however, to be closely monitored by The Icelandic Meterological Office.
Mýrdalsjökull is a glacier in the south of the Icelandic highlands. It is the country's fourth largest ice cap, covering nearly 600 kilometres squared, and its highest peak is almost 1500 meters tall. It is most well-known for sitting atop the notorious and explosive volcano, Katla.Mýrdalsjökull is visible from Route 1 on the South Coast, sitting to the north of the village of Vík.
Eruptions beneath Mýrdalsjökull
Since 2010, the world has known of the volcano beneath Eyjafjallajökull; few, however, are aware of the much larger volcano right beside it. Mýdalsjökull conceals Katla, one of the country’s most active volcanoes, having erupted, on average, once every fifty years since 930 AD. Because of the glacier above it, these eruptions tend to cause enormous ash clouds.
The last major eruption beneath Katla was in 1918, in which such huge lahar floods occurred that the southern coastline was extended five kilometres outwards. This area is also very susceptible to glacial floods, or jökulhlaups, during eruptions, even when the lava does not break through the surface of the ice.
Historically, the area was little settled for this reason.
Katla is connected to the same volcanic system as Eyjafallajökull and usually erupts violently a few years after. As the ex-president, Ólafur Ragnar Grímsson said in 2010:
‘The time for Katla to erupt is coming close… it is high time for European governments and airline authorities all over Europe and the world to start planning for the eventual Katla eruption’
Katla is monitored heavily, and roads around it closed when seismic activity increases. All road closures around Iceland can be found on Road and Coastal Administration's website.
Tours on Mýrdalsjökull
While there are no eruptions immediately imminent, tours continue to run on Mýrdalsjökull, allowing visitors to enjoy the glacier. It is, for example, possible to snowmobile across its surface throughout the year and take ice caving tours beneath it from October to April, with departures from both Reykjavík and Vík.
Considering the ice caves under Vatnajökull glacier are usually only accessible from November to March, this provides a wider window of opportunity for travellers to Iceland outside of the depths of winter. It should be noted that the caves in Mýrdalsjökull do not have the same blue ice, however.
Tours around Mýrdalsjökull
Mýrdalsjökull can be seen on all South Coast tours that reach Vík and beyond in clear weather. It can also be seen from above on helicopter tours that depart from Reykjavík.
The best perspectives of the glacier, however, can be found on the popular Fimmvörðuháls hiking trail, which goes between Eyjafjallajökull and Mýrdalsjökull. Part of this hike can be done in a day, or you can take the complete route from Þórsmörk to Skógar on a three-day trek.
Gigjokull is one of two glacier outlets from the glacier volcano Eyjafjallajokull, the other being Steinholtsjokull.
The 2010 Eyjafjallajokull eruption was close to the head of Gigjokull. Gigjokull empties out of the summit crater area at 1600 meters (5249 feet), flows across the ice cap to 1500 meters (4921 feet) and then descends in an icefall down 200 meters (656 ft). Water flowing from Gigjokull enters the Markarfljot river and eruptions in the area have caused great glacier bursts, 2010 being the latest example.
Stakkholtsgja is an up to 100 meters deep and 2 kilometers long canyon in South Iceland.
The canyon is located near the entrance to Thorsmork. It has a narrow riverbed and ends in a beautiful waterfall.
Valahnukur is a mountain in the beautiful Thorsmork valley in South Iceland.
Valahnukur is a popular hiking trail, as it offers a magnificent view of the area, which is one of Iceland's most beloved attractions.
