What Types Of Volcanoes Are In Hawaii?

The Hawaiian islands are home to some of the most active and spectacular volcanoes on Earth. If you’re short on time, here’s a quick answer to your question: Hawaii’s volcanoes are shield volcanoes that erupt fluid basalt lava in effusive eruptions that slowly build up the landscape over time.

In this comprehensive guide, we will explore the volcanic origins of the Hawaii islands. We’ll look at how the Hawaiian hotspot led to repeated volcano growth on the seafloor, eventually emerging from the ocean as stunning volcanic islands.

We’ll learn about the major volcanoes that form the high points of the islands. And we’ll examine the key characteristics of Hawaiian volcanoes that make them unique, like their shield shapes, basalt composition, rift zones, and effusive eruptions.

The Origins of Hawaiian Volcanoes at the Hawaiian Hotspot

The Hawaiian Hotspot Deep Below the Pacific Ocean

The Hawaiian islands were formed by a hotspot deep underneath the Pacific Ocean floor (over 1,800 miles deep!). This hotspot is a plume of hot, molten rock rising up from near the Earth’s core. It is estimated to be 50-100 miles across.

As the Pacific tectonic plate slowly drifts over this hotspot at about 1 inch per year, the hotspot partially melts the oceanic crust and produces magma that erupts through the seafloor to form volcanoes.

The Hawaiian hotspot is believed to have been active for at least 80 million years. As the Pacific plate drifts northwestward, the hotspot remains stationary, creating a chain of volcanoes across the ocean floor.

Currently the hotspot sits below the southeast coast of the Big Island of Hawaii, where Kilauea and Mauna Loa volcanoes are very active.

Repeated Volcano Growth as the Pacific Plate Moves

As the Pacific plate drifts over the hotspot, volcanoes begin to form and then become inactive as they move away from the hotspot. There are over 80 volcanoes in the Hawaiian island and underwater volcano chain, stretching over 1,500 miles.

The oldest volcano in this chain, Meiji Seamount, is located over 2,000 miles northwest of Hawaii near the Aleutian Trench and is 80 million years old.

New volcanic islands form as lava erupts through the ocean crust above the hotspot. Lava flows build up over hundreds of thousands of years to form tall volcanic mountains. Erosion wears down the islands once they drift away from the hotspot.

This explains why the southeastern Hawaiian islands closest to the hotspot (Hawaii and Maui) have large, high mountains, while islands further northwest (Oahu and Kauai) are older and more eroded.

It is truly remarkable that tiny islands like Hawaii were built up from the seafloor by countless eruptions from the hotspot below. Visitors to Hawaii can experience the raw geologic power still being unleashed on the Big Island today.

The Major Hawaiian Shield Volcanoes

Kilauea – One of the World’s Most Active Volcanoes

The Kilauea volcano on Hawaii’s Big Island is one of the world’s most active volcanoes. It has been continuously erupting since 1983, producing slow-moving lava flows that have buried over 50 square miles of land. Kilauea is the youngest and southeastern most volcano in the Hawaiian chain.

Its eruptions are effusive, meaning lava flows out steadily as opposed to building up pressure and exploding violently. This makes Kilauea a “shield volcano,” built up over time by fluid lava flows.

Mauna Loa – The Largest Volcano on Earth

The Mauna Loa volcano makes up over half of Hawaii’s Big Island. It rises 13,679 feet above sea level, making Mauna Loa the largest volcano on Earth in terms of area covered. Although not erupting currently, it has erupted 33 times since written history began in 1843, with eruptions lasting between a few months to over a year. Its large size is due to lava flows that have traveled all the way to the ocean and spread out under the water.

Haleakala – The Wide Volcanic Crater on Maui

Haleakala is a unique shield volcano on the island of Maui distinguished by its extremely wide crater at over 7 miles across. The name Haleakala means “House of the Sun” in Hawaiian. According to legend, the demigod Maui captured the sun at Haleakala to make the days longer.

The volcano last erupted around 1790 but remains active with possible future eruptions. Haleakala rises 10,023 feet above sea level, and its summit offers stunning sunrise views above the clouds.

Kohala – The Oldest Hawaiian Shield Volcano

The Kohala volcano on Hawaii’s northwest tip is the oldest of the Hawaiian Island volcanoes, last erupting 120,000 years ago. As the Pacific tectonic plate moves northwest over the Hawaiian hotspot, volcanoes like Kohala move off the hotspot after forming and go extinct.

At one million years old, Kohala is thus highly weathered and eroded compared to the still active volcanoes. Now sliced by deep river valleys and waterfalls, Kohala was once over 13,000 feet tall like Mauna Loa and Mauna Kea.

Unique Characteristics of Hawaiian Volcanoes

Shield Shapes Built by Fluid Lava Flows

The Hawaiian volcanoes are known for their broad, gently sloping shield shapes. This shape is created as fluid basalt lava pours out quietly from the vents and rift zones, flowing easily downslope for many miles.

The fluid flows stack up over hundreds of thousands of years to build the characteristic shield profile with slopes of only 5-10 degrees.

Fluid Basalt Lava Composition

The fluid nature of Hawaiian lava that enables it to flow so far is due to its chemical composition. Hawaiian lava tends to be low in silica, making it very hot and fluid. Temperatures can reach 2,120°F as the molten rock pours from volcanic vents.

The lava flows can travel all the way to the ocean while remaining hot and fluid.

Rift Zones Where Volcanic Activity is Focused

Much of the lava erupts from long fractures in the volcanoes called rift zones. The island’s largest volcanoes, Mauna Loa and Kilauea, have two prominent parallel rift zones extending down their flanks.

About 95% of historical eruptions in Hawaii have occurred along one of these rift zones, according to the USGS. This concentration of eruptive vents is unique to shield volcanoes like those found in Hawaii.

Mostly Effusive Eruptions Gradually Adding Land

While explosive eruptions do occur occasionally in Hawaii, most eruptions are effusive, characterized by the outpouring of lava onto the surface. Through continual effusive activity concentrated along rift zones, the Hawaiian volcanoes have gradually added land to the islands over hundreds of thousands of years.

In fact, the island of Hawaii continues to grow nearly 1 square mile every year as lava from Kilauea and Mauna Loa adds new land area.

Conclusion

The Hawaiian islands showcase shield volcanoes at their finest. As the Pacific plate glides across the deep Hawaiian hotspot, volcano after volcano grows from the seafloor, eventually rising as stunning volcanic islands.

Fluid lava flows gradually build up the classic shield shapes over hundreds of thousands of years. Hawaii owes its existence to the volcanoes produced by this hotspot, which continues fueling active eruptions today on the Big Island.

Understanding the origins and characteristics of Hawaiian volcanoes provides deeper insight into the geologic processes that built these remarkable islands.

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