The Hawaiian Islands are at the southeast end of a chain of volcanoes that began to form more than 70 million years ago. Each island is made of one or more volcanoes, which first erupted on the floor of the Pacific Ocean and emerged above sea level only after countless eruptions. Presently, there are six active volcanoes in Hawaii.
The USGS Hawaiian Volcano Observatory (HVO) is responsible for monitoring six active volcanoes on the Islands of Hawai‘i and Maui. The Island of Hawai‘i, with four active volcanoes, is liveliest. Between 1912 and 2012, there were nearly 50 Kīlauea eruptions, 12 Mauna Loa eruptions, and one Hualālai intrusion of magma. Mauna Kea most recently erupted only about 4,000 years ago. Kama‘ehuakanaloa (formerly Lō‘ihi Seamount), the submarine volcano located off the south coast of Kīlauea, erupted twice between 1950 and 1996. The Island of Maui has one active volcano, Haleakalā, which has erupted at least 10 times during the past 1,000 years.
Kīlauea, the youngest and most active volcano on the Island of Hawai‘i, erupted almost continuously from 1983 to 2018 at Pu‘u‘ō‘ō and other vents along the volcano's East Rift Zone. From 2008 to 2018, there was a lava lake within Halema‘uma‘u crater at the volcano's summit. In 2018, Kīlauea experienced the largest lower East Rift Zone eruption and summit collapse in at least 200 years. An eruption from December 2020 to May 2021 fed a lava lake in Halema‘uma‘u crater at the summit. Since September 29, 2021, an eruption has been ongoing within Halema‘uma‘u crater. About 90 percent of the volcano is covered with lava flows less than 1,100 years in age.
Mauna Loa, the largest volcano on Earth, has erupted 33 times since 1843. The most recent eruption in 1984 lasted 22 days and produced lava flows which reached to within about 7.2 km (4.5 miles) of Hilo, the largest population center on the Island of Hawai‘i. Lava flows less than 4,000 years old cover about 90 percent of the volcano.
Hualālai, the third most active volcano on the Island of Hawai‘i, has erupted three times in the past 1,000 years and eight times in the past 1,500 years. The most recent eruption in 1801 generated a lava flow that reached the ocean and now underlies the Kona International Airport. Lava flows less than 5,000 years old cover about 80 percent of the volcano.
Mauna Kea, the highest volcano on the Island of Hawai‘i, erupted most recently between about 6,000 and 4,500 years ago from at least seven separate summit-area vents, producing lava flows and cinder cones. Glaciers covered parts of the volcano's summit area during the recent ice ages, the only Hawaiian volcano known to have been glaciated.
Kama‘ehuakanaloa (formerly Lō‘ihi Seamount), the only known active Hawaiian submarine volcano, erupted most recently in 1996 during an earthquake swarm of more than 4,000 events that were recorded by the HVO seismic network. The volcano's summit is about 969 m (3,179 ft) below sea level, located 30 km (22 miles) southeast of the Island of Hawai‘i.
Haleakalā, the only active volcano on the Island of Maui, erupted most recently between about 600 and 400 years ago. In the past 1,000 years, at least 10 eruptions produced lava flows and tephra cones from the rift zone that crosses the volcano from southwest to east and through Haleakalā Crater.
The USGS Hawaiian Volcano Observatory (HVO) is also responsible for monitoring active volcanoes in American Samoa, which include: