Akun Island columnar basalt in the Aleutian Islands, Alaska

Many of the islands of the Aleutians are made up of an unusual geologic formation called columnar basalt. These formations are formed by the cooling of igneous materials. The Aleutians are part of the Pacific "Rim of Fire", made up of numerous volcanoes and geologically active landforms. In this image, biologists with the Alaska Maritime National Wildlife Refuge, explore a sea cave.