Iceland sits on the mid-Atlantic ridge, the meeting point of the North American and Eurasian plates. These are moving apart from each other. Across Iceland it's common to find fissures, where the surface of the earth is literally ripped apart.
Although it's since been filled in somewhat by rubble, the depths of the Grjótagjá fissure still steam, and its caves contain thermal springs that are up to 120°F, too hot to swim comfortably, and with a high risk of collapse.
East of Mývatn and the Krafla volcanic region, the landscape becomes desolate. Grey expanses of volcanic rubble stretch for tens of kilometers, and the region is too arid for plant life to take hold. The strongest illustration is the sudden absence of grazing sheep, the otherwise ubiquitous obstacles in Icelandic driving.
The sudden appearance of the Jökulsá á Fjöllum ("Glacial River in the Mountains") is a surprise. It flows from the massive Vatnajökull, the ice cap that covers 8% of the country. The river flows into the canyon Jökulsárgljúfur, which was primarily formed by a catastrophic volcanic eruption and the ensuring flooding, instead of the more typical long-term river erosion.
The edges of the canyon are lined with columnar volcanic basalt, making it look eerily like it was designed and constructed by an ancient culture.
It's also home to some of Iceland's most spectacular waterfalls. Our first stop is the beautiful and elegant Selfoss.
Its spray is visible from several kilometers away. You hear it long before you ever see it. It takes several minutes to take in its scale.
The canyon drops steeply and widens considerably at Dettifoss, where the volume of water and huge vertical drop earns it the title of "Europe's most powerful".
No place on the western rim of the canyon is immune from the spray, and the trails are slippery and eroding rapidly. Sightseers hide their cameras inside their raincoats until they find the right moment to whip them out for snapshots. Faces glisten with water droplets and shine in wonder and awe.
Downstream from Dettifoss is Hafragilsfoss, a lonely and little-visited spot, although unexpectedly verdant and beautiful. A trail leads down from the upper canyon rim, but the drizzly weather keeps us from exploring it today.
Further north along Jökulsárgljúfur canyon is Vesturdalur, an area known for its distinctive volcanic rock formations. We planned to spend the rest of the day hiking here, but rainy weather moves in just after we pitch our tent.
We welcome the chance to rest and alternate between napping and reading until morning.