Within the summit caldera of Mount Kilauea
at Hawaii Volcanoes National Park
is a crater called Halemaʻumaʻu, nearly 3,000 feet in diameter and often showcasing a plume of sulfur dioxide smoke. Halemaʻumaʻu is still active with an underground lava lake and occasional eruptions! The lava lake once existed above ground, as recorded when the first English explorers to discover the crater noted their observations. The landscape is constantly changing here. In 2008, an explosive incident widened the crater by up to 30 feet.
In 1823, English missionary William Ellis wrote the first published description of Halema'uma'u Crater. Forty years later in 1866, Mark Twain said that looking at the crater was like "gazing at the sun at noon-day, except the glare was not so white." The crater floor, though not covered by lava at the moment, is a volatile landscape that can erupt lava or vent sulfur dioxide at any moment.