| Hverfell is a tuff cone that grew along the east shore of Mývatn in early historic time. The cone is not unlike Diamond Head on Oahu, Hawaii although the shoreline of Mývatn bears no resemblance to Waikiki. |  |
| Hverfell is a tuff cone that grew along the east shore of Mývatn in early historic time. The cone is not unlike Diamond Head on Oahu, Hawaii although the shoreline of Mývatn bears no resemblance to Waikiki. | |
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Hverfjall overlooks an area of medieval basaltic flows known as Dimmuborgir ("Dark Castle"). In this photo you can see the roughly circular outline of the Dimmuborgir area. The south shore of Mývatn is seen in the distance. |
| Within Dimmuborgir there are several places where vertical slickensides are visible, suggesting that the central portion of the region was down-dropped, probably after the magma chamber underneath was evacuated during an eruption. |  |
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The plate boundary between the North American Plate (far side) and the Eurasian Plate (near side) is seen where the rift crosses into Krafla caldera. This area is near Myvatn just north of the Namasfjall Geothermal Station. The station is the site of the only volcanic eruption caused by human activity. A drillhole penetrated a magma chamber below and caused about 30 tons of lava to erupt before the tiny vent choked itself off. |
| A trail leads to the rift as it cuts across the Krafla caldera floor. This was the site of the 1975-1980 eruptions known as the "Krafla Fires". This image shows lava flows as they crossed the patterned ground of the tundra that covers the caldera floor. |  |
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Geothermal areas along the rift in Krafla provide the setting with an other-worldly feeling with strong sulfurous odors, mineralized rocks and regolith, fumarolic steam, and bubbling springs. |
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Straddling the mid-Atlantic plate boundary, in 1996, along the 1975-1984 eruptive fissure in Krafla Caldera, Iceland: My right foot is on the North American Plate and my left is on the Eurasian Plate. I visited Iceland as the guest faculty advisor for the Geology Club at Utrecht University in the Netherlands. I revisited the caldera in August 2002 and July 2004 with student trips sponsored by the Geological Society of America. |
| The rift through Krafla caldera is generally marked by a ridge composed of numerous spatter cones. Several lava tubes are present along the rift. |  |
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This lava tube had collapsed in a couple of parts to provide light far back in the tunnel. |
| In case there was any doubt that rifting is active in Krafla caldera, this photo presents a strong argument for crustal extension. The lava flows on the right were erupted from the main fissures and almost flowed into the peripheral fractures. |  |
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