Markarfljotsgljufur

The Markarfljot has cut a canyon through soft highland rock that runs for close to twenty kilometres and reaches around two hundred metres deep, with walls of layered tephra and palagonite in browns and greys. The river below is heavy with glacial silt off Myrdalsjokull and Eyjafjallajokull, and in flood it moves an enormous volume - the 2010 Eyjafjallajokull eruption sent meltwater down this channel and forced the ring road bridges to be cut deliberately to save them. The best viewpoint is a short detour from the Laugavegur route near Emstrur, which many walkers skip because it adds an hour to a long day.

What you actually see

• A canyon around two hundred metres deep - layered tephra and palagonite walls.
• Glacial water below - silt off two ice caps moving through it.
• The 2010 flood route - meltwater from Eyjafjallajokull came down this channel.
• A detour most walkers skip - about an hour off the Laugavegur near Emstrur.

When to go

July to early September. Half a day.

Honest expectations

Access by road means fords that are dangerous after rain or on warm afternoons. The rim is unfenced with a two hundred metre drop and the edge is undercut in places. There is a hut at Emstrur and nothing else.

Nearby

Thorsmork is south-west; Landmannalaugar is at the trail's far end.