340 m, hour two
The moss line, where green gives up
Below this height, Iceland pretends to be gentle. Above it, the ground is last year's rock, sharp underfoot and faintly warm through your boot soles. Everyone kneels and puts a palm down. Nobody is ever ready for the warmth.
640 m, hour three, the windy mile
Gjallar ridge, the island on both sides
Twenty minutes of walking a line between two views that do not belong on the same planet: green farmland to the west, a black lava field to the east still steaming in stripes. This is where the weather makes its decision, and where Sigrún makes hers.
890 m, hour four
Lunch on the rim of a breathing crater
The bowl below you exhales steam from a dozen vents, and when the wind drops you can hear it: a low mineral hiss, the mountain settling into its new shape. You will eat a sandwich fifty metres from the edge and remember it at odd moments for the rest of your life.
Ground temperature at your lunch spot: 41 °C. Bring chocolate; it melts into something better.Going up this week
Departures Wednesday through Sunday, 8:30, from the Rauðaskál car park. Minimum age twelve. When the mountain closes, everyone rebooks or gets every krona back the same day.
Book a place, 12,900 ISKSigrún Treks ehf, licence FER-2214, partnered with ICE-SAR search and rescue.
Photographs: Icelandic Department of Civil Protection and Jeffrey Paul, both CC0.