These are terrain sections, not prescribed walking days. Where one research section covers a long distance, it is split at useful landmarks so you can shorten a day or rebalance the itinerary around it.
The trail leaves Landmannalaugar straight into the Laugahraun lava field, where the tread threads between blocks of black lava under bright green moss, then climbs onto the plateau steadily rather than steeply over the first five kilometres. The surface turns to pumice, ash and loose obsidian, glassy black chips that skate underfoot on the steeper pitches, with fumaroles steaming beside the path and a hot spring at Stórihver. From there to about km 16 the walking stays high and open across a rolling waste of old snow, dark obsidian and stained rhyolite, dipping through a run of ravines where meltwater streams have cut in beneath the snow. This is the coldest and least sheltered ground on the route, and those ravine crossings are why it is slower than the distance suggests: the snow rots from below, so a crust thins without showing it. The stretch finishes with the long stony clatter down off Jökultungur, steep enough to want careful feet, with Tindfjallajökull, Eyjafjallajökull and Mýrdalsjökull all in view on a clear day, onto green moss and flat ground at the bottom.
Navigation: Posted the whole way and busy in season, so in clear weather a line of walkers is usually the clearest marker there is. The problem here is visibility rather than route choice: on the snowfields either side of Hrafntinnusker there is nothing to steer by except the posts, and cloud settles on this plateau and stays. Two memorials stand beside the path, one to a walker who died in a blizzard in late June within sight of the hut, which is a fair indication of what going wrong on this ground looks like.
In poor weather: Snow lies here through the summer and melts from underneath, so a bridge that held in the morning may not hold in the afternoon; the ravines between km 10 and km 16 are where that matters. Rain makes the fine sediment on the rhyolite slopes and the loose obsidian genuinely slippery, and the Jökultungur descent is the worst of it. There is no wind shelter above about km 5, and wind lifts the fine volcanic ash into everything, eyes and tent zips included.
Escape options: None worth the name. From roughly km 5 the honest choices are back to Landmannalaugar or on across the plateau. The Hrafntinnusker hut at km 10.2 is shelter, not an exit: there is no road to it.
Four quite different pieces of walking strung together, which is why one ascent figure flatters it. From the Grashagakvísl flats to Hvanngil the ground is green and comparatively sheltered, ash and cinder vehicle tracks past a big lake, with the first easy fords in it. Then the route commits to the black sand for a dozen kilometres, flat and dark and scattered with lava bombs, quick underfoot with nothing at all to hide behind. After Emstrur it turns to canyon country, moss over rock, with a steep drop and a steep climb either side of the footbridge in the Fremri-Emstruá gorge and a last cold wade across the wide gravel bed of the Þröngá. Þórsmörk then arrives all at once: birch woods, shelter, shade and roots underfoot, the first real green since Landmannalaugar. It does not last. The section ends by climbing straight back out from Básar, roughly 760 m in six and a half kilometres, up the Strákagil gully and along the narrow ridges of Kattarhryggir and Heljarkambur onto the edge of the pass.
Around km 18 to black sand begins; flat9 km
black sand begins; flat to steep drop into the Fremri-Emstruá gorge to a footbridge12 km
steep drop into the Fremri-Emstruá gorge to a footbridge to Around km 6122 km
1,530 m total ascent across this broader terrain section
Navigation: Well marked and mostly obvious, but three things catch people. Ford crossing points are marked and shift slightly year to year as the braided channels move, so cross where the markers put you rather than where the water looks shallowest. Emstrur is invisible until the last moment, which unsettles walkers counting it down. And on Morinsheiði the tread is faint across cinders with sheer drops on several sides, which is the one place above Þórsmörk where losing the line in cloud is dangerous rather than merely annoying.
In poor weather: Mostly a question of rivers. Þröngá and Bláfjallakvísl take both rainfall and glacier melt, so they rise through a warm afternoon as well as after rain, and an early crossing is a different crossing from a late one. The Krossá behaves the same way and is the one that can stop a plan outright, since its footbridge is repositioned as the channels move and removed in severe floods. On the sand between Hvanngil and Emstrur there is no shelter for a dozen kilometres and wind picks up the 2010 ash and drives it down the valley, which makes a flat profile far harder than it reads. Þórsmörk sits low and wooded, so conditions on the valley floor tell you nothing useful about the ridges above Básar.
Escape options: Real ones, unlike the first section. Álftavatn (km 21.2) and Hvanngil (km 25) sit on Fjallabaksleið syðri (F210), and Emstrur (km 36.9) on a spur off Emstruleið (F261); FÍ describe both as 4x4 routes with unbridged rivers, so leaving that way depends entirely on who happens to be at the hut. Þórsmörk at km 52.7 is the dependable one, with road access down F249 and scheduled highland buses through the season. After Básar it turns committing again: once you are on the ridges past km 56, the choices are back down to Básar or on over the pass.
The top of the pass, then sixteen kilometres of almost unbroken descent. The first three kilometres are what people come for: the 2010 lava of Goðahraun between the craters Móði and Magni, jagged and still unconsolidated, with Eyjafjallajökull on one side and Mýrdalsjökull on the other and snowfields lying between them well into the summer. It is high, flat, featureless and marked by yellow poles, and in cloud it is exactly as blank as that sounds. Past Baldvinsskáli the ground and the interest fall away together: a long stony 4x4 track down cinder fields, easy going and dull. The route comes back to life at the footbridge over the Skógá, where the track ends and a path takes over along the lip of the river gorge, staying with it for the last eight kilometres past a chain of some 26 waterfalls to Skógafoss and the staircase down to the road. That lower path is earth and grass rather than rock, so it is also the one part of the route that gets properly muddy.
Navigation: Yellow poles carry the line across the lava and snow of the pass and are the only guide there is up there. Two things confuse people. There are two huts, Fimmvörðuskáli about 500 m west of the line and Baldvinsskáli on it, and walkers have reported two sets of same-coloured markers in that area which diverge and then rejoin. Below the Skógá bridge navigation stops being a question at all: the river is beside you the whole way down.
In poor weather: The pass is where weather decides the day. It is a flat plateau at around 1,000 m between two icecaps, it takes the wind unfiltered, and in cloud the poles are the only thing to follow across lava and snow. Snow lies late around the huts and on the slopes either side of them, and it turns slippery. Lower down the sensitivity inverts: the waterfall path is earth and grass, it goes muddy and slick in rain, and it runs within a few metres of the gorge edge in several places, which is where wet ground stops being merely uncomfortable.
Escape options: Nothing sideways. Fimmvörðuskáli (km 64) and Baldvinsskáli (km 65.1) are shelter on the pass, not exits. The only vehicle access is the rough 4x4 track between Baldvinsskáli and the Skógá, and it is a jeep track rather than a road, so on foot the practical exit is forward: from the top it is downhill the whole way to Skógar and the Ring Road, and past the Skógá bridge the path is easy and well used.