These crater groups
on the lake shore were formed by steam explosions
when glowing lava poured into a lake. The various forms of the craters
tell how they took shape as the steam eruptions continued.
Eruptions occur in many craters. A platform of scoria (volcanic gravel) builds up.
Elevated crater rims have not formed yet.
The eruption continues in one crater. A crater rim is formed.
The eruption looses vigour and a small crater is formed inside the bigger one. (Note
the cow for scale).
Sometimes molten lava is splashed on top of the crater rims and forms solid rock.
Einarsson, Á. 1982. The palaeolimnology of Lake Myvatn, northern Iceland: plant and animal microfossils in the sediment. Freshwater Biology 12: 63-82.
Einarsson, Á. 1991. Lífríki í 2000 ár. Pp. 320-336 in Náttúra Mývatns, eds. A. Garðarsson & Á. Einarsson. Icelandic Natural History Society, Reykjavík.
Thorarinsson, S. 1953. The crater groups in Iceland. Bulletin volcanologique 2: 1-44.