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.
Hawaiʻi sits over a ‘hot spot,’ the Hawaiian hot spot.
It’s one hot spot, but lots of volcanoes have formed over it. The Islands are above a moving sea floor of the North Pacific Ocean (the Pacific Ocean is mostly floored by a single tectonic plate known as the “Pacific Plate.”)
The Pacific Plate is moving over the layer in the Earth known as the Asthenosphere. This movement takes it to the northwest. As the plate moves over a fixed spot deeper in the Earth where magma (molten lava) forms, a new volcano can punch through this plate and create an island.
As the plate moves away, the volcano stops erupting and a new one is formed in its place. With time, the volcanoes keep drifting westward and getting older relative to the one active volcano that is over the hot spot.
As they age, the crust that they sit on cools and subsides. This, combined with erosion of the islands, once active volcanism stops, leads to a shrinking of the islands with age and their eventual submergence below the ocean surface.
Each island is made up of at least one primary volcano, although many islands are composites of more than one. The Big Island, for instance, is constructed of 5 major volcanoes: Kilauea, Mauna Loa, Mauna Kea, Hualālai and Kohala (the island is still growing, but is basically about 400,000-years old.)
About 40-million years ago, the Pacific Plate changed direction from north to northwest – so the Emperor Seamounts run more north-south, the Hawaiian Ridge north-westerly.
Midway Island is 27.7-million years old; Meiji Seamount the northern part of the Emperor Seamount (near the end of the Aleutian chain) is about 80-million years old.
All of these are still youngsters, when you look at the perspective, say, of the dinosaurs. The Islands weren’t even a glimmer in anyone’s eyes when dinosaurs walked the Earth; sixty-five million years ago the last of the non-avian dinosaurs went extinct, after living on Earth for about 165-million years. (USGS)
If all of Earth time from the very beginning of the dinosaurs to today were compressed into 365 days (1 calendar year), the dinosaurs appeared January 1 and became extinct the third week of September.
Using this same time scale, the Earth would have formed approximately 18.5-years earlier. By comparison, people have been on earth only since December 31 (New Year’s eve.) (USGS)
While we typically think of and/or hear news reports of eruptions on Kilauea and Maunaloa, presently, the US Geological Survey (USGS) Hawaiian Volcano Observatory (HVO) monitors the six currently active volcanoes in Hawai‘i.
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.
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. Since then, there have been periodic eruptions in and nearby 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. Several summit eruptions since December 2020 have generated lava lakes that have been slowly filling in the collapsed area, including 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 34 times since 1843. An eruption 1984 lasted 22 days and produced lava flows which reached to within about 4.5 miles of Hilo, the largest population center on the Island of Hawai‘i.
The most recent eruption in 2022 lasted two weeks and erupted lava flows that came to within 1.7 miles of the Daniel K Inouye Highway (Saddle Road). 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 3,179 ft below sea level, located 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. (All here is from the US Geological Survey (USGS.))
