Volcanoes

Volcanoes are monuments to Earth's origins, evidence that its primordial forces are still at work. Over time, these prodigious land builders have created the Hawaiian island chain itself. Kīlauea and Mauna Loa are still adding to the island of Hawaiʻi and put this incredible phenomenon on full display.

 

 

Generalized boundaries of the five volcanoes on the island of Hawaiʻi: Kīlauea, Mauna Loa, Mauna Kea, Hualālai, and Kohala (NPS Graphic)

Island of Giants

Lapakū i Hawaiʻi ka wahine, aʻo Pele
(Pele is most active on Hawaiʻi Island)
Although Kīlauea and Mauna Loa are by far the most active, they combine with three other volcanoes to make up the Island of Hawaiʻi. Mauna Kea, Hualālai, and Kohala all loom to the north of Hawaiʻi Volcanoes National Park.

These three volcanoes are much older and less likely to erupt than their younger siblings to the south. However, Hualālai, upon which Kailua-Kona is built, last erupted in only 1801. It is still considered active. Mauna Kea, which last erupted an estimated 4,500 years ago, is also likely to erupt again, although its periods of quiet are much longer. Kohala, the oldest volcano on the island, has concluded its period of eruptive activity.

 

Why Are Volcanoes Here?

The eight Hawaiian Islands we know today are only the most recent formations in a chain of over 80 volcanoes that stretch for thousands of miles to the northwest, both above and below sea-level. The further southeast in this chain, the younger the volcano, ending with the island of Hawai’i and Lō‘ihi, a growing volcano still beneath the ocean’s surface.

All of the volcanoes (both active and inactive) in this long chain formed because of the Hawaiian hot spot, a stationary plume of super-heated material deep in the earth. Heat from this material rises, eventually melting rock into magma. The magma then continues to rise. When some of it pushes its way to the surface, a volcanic eruption takes place.

The exact size of the Hawaiian hot spot is not fully understood, but it is large enough to encompass most of the Island of Hawaiʻi. Some scientists estimate the hot spot to be about 200 miles across, with much narrower vertical passageways that feed magma to the individual volcanoes.

Meanwhile, the Pacific Plate, one of the several tectonic plates that move around the surface of the earth, migrates slowly to the northwest. As it moves an estimated 2-4 inches per year, it carries with it any land that formed during volcanic eruptions.

The result is like an assembly line. The hotspot stays in one place, producing new land through eruptions, and the pacific plate carries them away. The geological formation of the Hawaiian Islands through this process mirrors the legendary journey of the Hawaiian volcano deity Pele to the island of Hawaiʻi.

Eventually, the Island of Hawai’i too will be moved by the tectonic plate away from the hotspot. It will follow in the footsteps of the older Hawaiian Islands to the northwest, and volcanic activity on the island will cease. New volcanic islands, still unborn, will come up behind it.

 

A simplified cross-section of Hawaiʻi Island and the Hawaiian hot spot (NPS Graphic)

 

Additional Resources