Volcanic ash (tephra) crater Hverfjall (Hverfell), 140m deep, more than 1 km across, at Myvatn, northern Iceland, Iceland, Polar Regions

The Hverfjall crater, a tephra cone or tuff ring volcano in Northern Iceland. The crater is approximately 1 kilometre in diameter; Skutustadahreppur, Northeastern Region, Iceland

Snorkelers getting ready to enter the water from a snorkelling tour boat operated out of Maui, Hawaii. They are located next to the backwall of Molokini Crater which is a volcanic tuff cone, Maui, Hawaii, United States of America