Mar 5, 2025
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Aurora borealis at Krafla lava fields
1997: Krafla caldera sits upon the divergent boundary between the North American Plate and the Eurasian Plate (you can actually stand astride the boundary and have a foot on each). It would have changed quite a bit in the 24 years since I was there.
Mývatn Maars
When lava hits water, it tends to explode. The heat causes the water to flash to steam and expand, tearing the rock apart and blasting out fragments. Those fragments tend to pile up, forming cones around the location where the water and lava met.
Those cones are called maars (or rootless cones since they’re not connected to a magma system below) and this spot is loaded with them. This is Lake Mývatn in north-central Iceland, north of the volcano Krafla. The lake originally formed in a basin left behind after the end of the last glaciation – the basin was surrounded by glacial moraines that held in the water.
2300 years ago, a large fissure eruption took place north of the lake, sending lava all the way to the Arctic Ocean. The lava flow interacted with the waters in the lake, causing explosions and forming these maar volcanic cones.
That lava flow and repeated eruptions since then left their mark on the area, producing new cones and damming the lake at different edges.
The lake is the 6th largest in Iceland. Its waters freeze over in the winter and melt in the summer, setting up a eutrophic environment with heavy biological productivity. Algal blooms form in the summer, fed by nutrients from nearby springs that supply waters that are rich in nutrients and metals due to the hydrothermal systems nearby. Diatom-rich sediments from the lake are even dredged/mined as a resource in Iceland.
-JBB
Image credit: National Geographic Wallpaper http://travel.nationalgeographic.com/travel/365-photos/lake-mvatn-iceland/
Read more: https://notendur.hi.is/~arnie/geol.htm http://www.diamondringroad.com/myvatngeology.html http://www.hafro.is/Bokasafn/Greinar/oikos_32-82.pdf http://bit.ly/1B970zY
Steaming Fumarole at Krafla geothermal area in Iceland. A fumarole is an opening in the earth crust which emits steam and gases.
crater’s edge
Krafla