There are five active volcanoes in Hawaii: Lo'ihi, Kilauea, Mauna Loa, Hualalai and Haleakala. Lo'ihi is an underwater volcano; the other four volcanoes are above sea level.
Kilauea is Hawaii's most active volcano, with 62 eruptions recorded since the arrival of Europeans in Hawaii. Mauna Loa and Lo'ihi also have recorded activity in the 20th century. Hualalai and Haleakala are dormant but not classified as extinct. While their eruption activity is not as recent as the other free volcanoes, both are expected to erupt in the future.
Both Kilauea and Mauna Loa are active enough to present a threat to nearby human activity. These threats include lava flows, airborne lava fragments, volcanic gases, explosions, ground cracking and earthquakes. Even underwater eruptions present a hazard; explosions can occur when lava comes into contact with seawater. The U.S. Geological Survey's Hawaiian Volcano Observatory monitors these hazards and issues warnings when necessary.
Hawaii is also home to 10 extinct volcanoes. These 15 volcanoes are part of a larger chain known as the Hawaiian-Emperor Seamount Chain, and these volcanoes are the youngest in the chain. This volcano chain runs from the Hawaiian Islands northeast to Kamchatka, Russia. The volcanoes northeast of Hawaii have eroded below sea level and are no longer islands.