Ukinrek Maars, Volcanic crater system in Lake and Peninsula Borough, Alaska

Ukinrek Maars is a pair of water-filled volcanic craters on a low ridge south of Becharof Lake in Alaska's Aleutian Range. The western crater is elliptical, 105 by 170 m across and 35 m deep; the eastern crater, 600 m away, is circular, 300 m wide and 70 m deep, with a 49 m lava dome rising from its crater lake.

This crater system formed during an intense volcanic eruption that lasted ten days in March and April 1977. This was the first recorded volcanic activity at this location and represented a major geological event for the region.

The name Ukinrek comes from Central Yupik and was given shortly after the 1977 eruption; its literal translation is "Two Holes", referring to the pair of craters. The maars lie within the Becharof National Wildlife Refuge, on the Alaska Peninsula.

The maars lie in the Becharof National Wildlife Refuge, 2 km south of Becharof Lake and 12.5 km northwest of Mount Peulik, on a low ridge rising from the Bering Sea lowland. There are no roads or facilities; access is by floatplane or boat across the lake, then on foot. Plan for changeable coastal weather and carry everything you need.

The eruption ejected roughly 26 million cubic meters of tephra and produced around 900,000 cubic meters of lava. These massive volumes of volcanic material created clearly visible layers in the surrounding landscape that reveal the power of this sudden event.