We left the campground a little after 10am and drove to one of the parking areas below Fagradalsfjall. This stretch of Reykjanes had been quiet for about 800 years before 2021, when a fissure opened in the valley of Geldingadalur and ran for six months. A second fissure opened the year after in the next valley over, Meradalir, and a third the year after that, near a hill called Litli-Hrútur. Together these are known as the Fagradalsfjall Fires, a different eruptive system from the one that has been sending lava toward Grindavík since the end of 2023. We had seen the results of that second system from the campsite the night before. Today we were walking into the first one.

The trail starts with a gentle rise from the parking area, gradual enough to still feel like a warm-up. It doesn’t stay that way. After about half a mile the switchbacks begin, climbing roughly 1,000 feet over a mile or so of tight zigzags cut into the hillside. It is the steepest part of the whole hike, and by the top our legs knew it. Along the switchbacks and the ridge beyond them, poles marked the route at regular intervals, each one topped with a small amber light. They serve as emergency beacons, meant to guide hikers back to the trail if fog drops over the ridge, which it can do quickly and without much warning on this part of the peninsula. From the top of the switchbacks the trail levels out, running along a ridge with long stretches of open, uneven ground: loose gravel, volcanic rubble, and stretches of rock still holding the shape it froze in.

The contrast between old and new lava became obvious once we reached the high point above Stórhóll, looking down at the 2021 lava field. Older rock in this part of Iceland is covered in a soft grey green blanket of moss, built up over centuries. The 2021 field looked nothing like that. It was black, cracked, and almost entirely bare, young enough that it hasn’t had time to grow anything yet. Walking the ridge between older, mossed-over terrain and this raw black rock felt like walking across two different geologic ages in the space of a few hundred feet.

Life is starting to take hold on it anyway. Where the rock had cooled enough and sat undisturbed the longest, we found patches of dark, crusty lichen clinging directly to the stone, and beyond that, low mats of moss beginning to soften the edges. These are pioneer species. Lichens can grow on bare rock with no soil at all, and some of them fix nitrogen from the air, slowly building up the nutrients that moss needs to follow. Moss then builds up organic matter of its own, and over centuries that becomes the beginning of soil. It is a slow, specific sequence, and it is close in principle, if not in scale or chemistry, to the sequence that let early microorganisms begin altering bare rock and changing the chemistry of the planet billions of years ago. Nothing here is ancient. It’s the same basic process, just a few years old instead of a few billion.

We continued along the trail to the Meradalir viewpoint, looking out over the crater and lava field left by the 2022 eruption, which lasted only 19 days but filled the valley floor. From there the trail continues another few miles toward Litli-Hrútur, the youngest and largest lava field of the three, formed over 27 days in the summer of 2023 when lava poured out fast enough to connect with both older fields. We walked partway along that stretch, far enough to see the terrain change again, rougher and even less settled than what came before, before turning back the way we’d come. The whole hike out and back covered several miles and a few thousand feet of climbing and descending, most of it over ground that, geologically speaking, is barely old enough to have a name yet.

Leaving Meradalir

We left the Meradalir trailhead and drove southeast on Route 427 toward the Krýsuvík volcanic system, the next segment of the peninsula’s active fissure zone. Along the way we passed, without stopping, the crater Eldborg and the table mountain Geitahlíð rising beside it. Eldborg is the tallest of five craters strung along a volcanic fissure on the slopes of Geitafell, and Geitahlíð is itself an old shield volcano, flattened on top into the broad plateau shape that gives table mountains their name in Iceland. Both stayed in view for a few minutes before the road curved away from them.

Seltún

The road brought us to Seltún, the main geothermal area of Krýsuvík, sitting directly on the Mid Atlantic Ridge fissure zone. A boardwalk winds through the field, keeping visitors off ground that is genuinely unstable underfoot. Steam rose out of the hillside in several places at once, and the ground itself was stained yellow, orange, and red from the minerals carried up by the heat below. Mud pools bubbled slowly at a few points along the walk.

Grænavatn and Kleifarvatn

From Seltún we made a short stop at Grænavatn, a small circular lake a few miles south. It sits in an explosion crater and its water runs a deep, almost unnatural green, a color that comes from thermal algae and mineral crystals suspended in the water rather than from anything visibly alive on the surface. The lake is about 150 feet deep at its center. Kleifarvatn is the largest lake on the Reykjanes peninsula at roughly 3.5 square miles, and one of the deepest lakes in Iceland at around 320 feet. Its water is fed partly by geothermal sources in the ground beneath it, and the lake has been known to rise and fall by several feet after earthquakes, as fissures in the lakebed open or close. We stopped along the shore road for a few minutes, long enough to take in how much larger and darker the water was than the small crater lake we’d just left, then carried on.

Þorlákshöfn

We left the Krýsuvík area and drove east toward the coast, arriving at our new campground in Þorlákshöfn by evening. It’s a working harbor town, the only one on Iceland’s south coast between Grindavík and Höfn, and it still serves as a backup ferry port to the Westman Islands whenever weather closes the newer, shorter route from Landeyjahöfn.