A pseudocrater is rendered in silhouette against a volanic cone at sunset in Mývatn in northern Iceland. Mývatn is a lake that was formed approximately 2,300 years ago during a volanic period. The shorter hill is a pseudocrater, also known as a rootless vent. While it resembles a volcanic cinder cone, it formed through a different process. As basaltic lava flowed over soggy lake sediments, it flash heated the moisture into vapor, causing it to blast through the lava. Mývatn means lake with midge flies; the lake is infested with them during the summer months.