Few People Realize There’s A Second Active Volcano Right Here In Hawaii

The Hawaiian archipelago was created millions of years ago when underwater volcanoes emerged from the ocean’s surface. Each Hawaiian Island is home to at least one volcano, though Hawaii Island – the youngest of the main islands – consists of five volcanoes: Kilauea, Hualalai, Kohala, Mauna Kea, and Mauna Loa. While most people are familiar with Kilauea, one of the most active volcanoes on earth, not everyone remembers that Mauna Loa is actually larger than Kilauea and almost as active.

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Mauna Loa has long been considered the largest subaerial volcano on earth in terms of both mass and volume. Its peak is only 120 feet lower than its neighbor Mauna Kea, and is approximately 18,000 cubic miles in volume with gentle slopes.

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The slopes of Mauna Loa rise gradually more than 13,000 feet above sea level, and more than 16,000 below the surface. The ocean floor is also depressed by Mauna Loa’s great mass another 26,000 feet - making the entire volcano, from below the seafloor to summit, 56,000 feet in height. That’s nearly 20,000 feet taller than Mount Everest! The name Mauna Loa translates to "Long Mountain" in Hawaiian, an apt name for a volcano that accounts for more than half of Hawaii Island’s land mass.

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It is estimated that Mauna Loa emerged above sea level some 400,000 years ago and has been erupting for more than 700,000 years, though the oldest dated rocks are no more than 200,000 years old.

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U.S. Geological Survey/Flickr

The volcano last erupted from March 24 to April 15, 1984. There have been no fatalities caused by recent volcanic activity from Mauna Loa, but eruptions in 1926 and 1950 destroyed villages. In fact, the city of Hilo is partially built on top of lava flows from the late 19th century. Unlike Kilauea, eruptions of Mauna Loa are typically huge, producing rivers of lava that have continuously threatened the town of Hilo.

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R.W. Decker/Public Domain, Wikipedia

The volcano has erupted approximately 33 times since the first well-documented historical eruption in 1843, making it one of the world’s most active volcanoes. However, because the volcano isn’t currently erupting, it is often overshadowed by the neighboring Kilauea, which has been continuously erupting since 1983.

U.S. Geological Survey/Flickr

The Hawaiian Volcano Observatory has monitored Mauna Loa closely since 1912, and the volcano is part of the Decade Volcanoes program, which studies the world’s most dangerous volcanoes. After an extended period of quiet, Mauna Loa is certain to erupt again, and is closely monitored for signs of unrest.

Jai Mansson/Flickr

The summit area and southeastern flank of the volcano are a part of Hawaii Volcanoes National Park, which also includes Kilauea. In fact, Mauna Loa and Kilauea are actually connected - and it was once thought that Kilauea was simply a part of Mauna Loa, until its own set of lava tunnels were discovered.

Have you experienced the beauty – or danger – that is Mauna Loa? Share your stories with us on our Only In Hawaii Facebook page. You also might enjoy reading about these 12 incredible Hawaiian volcanoes.