|Akun Island Columnar Basalt - Alaska. Photo: Steve Hillebrand, U.S. Fish and Wildlife Service|
Columnar basalt is a geological formation that consists of closely spaced, vertically oriented basalt columns. These columns form when lava cools and contracts, creating cracks in the rock. The columns are typically hexagonal or pentagonal in shape, and they can range in size from a few centimeters to several meters in diameter.
Akun Island in Alaska is home to a spectacular example of columnar basalt. The columns on Akun Island are up to 60 meters (200 feet) tall and 3 meters (10 feet) in diameter. They are formed from lava flows that erupted from volcanoes on the island millions of years ago.
The columns can vary from 3 meters to a few centimeters in diameter, and can be as much as 30 meters tall. They are typically parallel and straight, but can also be curved and vary in diameter.