Information on the Mauna Loa Volcano in Hawaii
Mauna Loa is one of five volcanoes that make up the island of Hawaii in the state of Hawaii. It's one of the most active volcanoes on Earth and is the planet's largest volcano. Mauna Loa means Long Mountain; it's 60 miles long and 30 miles wide. At its summit, the volcano has a caldera named Moku`aweoweo. A caldera is a crater that forms when eruptions no longer support the cone of a volcano and it collapses inward. When the volcano erupts, it can spray fountains of lava into the air or create what are called curtains of fire as lava sprays up in a line.
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Size
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Mauna Loa rises from its sea floor base over 10.5 miles or 17 kilometers. From sea level, the volcano is about 2.5 miles or 4 kilometers high. The huge volcano has an area of 2,035 square miles--5,271 square kilometers--which is over 50 percent of the island of Hawaii. The volcano is so large that it is as big as about 85 percent of the rest of the other islands of Hawaii together. The volcano has a 400-mile (600-kilometer) circumference.
Age
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Mauna Loa is between 700,000 and 1,000,000 years old. The first eruption took place during the same time period that ranges from 700,000 to 1,000,000 years ago. The first subaerial eruption occurred 400,000 years ago. Subaerial means "under air" as opposed to under water. Rocks created from the volcano date back 100,000 to 200,000 years. Almost the entire surface of Mauna Loa is less than 10,000 years old. The oldest rocks of Mauna Loa are found in the Ninole Volcanic Series, a hilly rock formation created from the material of old eruptions.
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Eruptions
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Mauna Loa is a shield volcano, composed of layers of lava flows that build up to resemble a shield lying on the ground, curved side arcing up. Shield volcanoes are the largest of the volcano types. The first written reference to an eruption of Mauna Loa is a description given by one Keaweehu. He told of an eruption that took place in 1780.
The next reference was in 1832, when a missionary saw Mauna Loa erupting from another island. The earliest well-documented eruption happened in 1843. Shield volcanoes have effusive eruptions, which are relatively quiet and not usually explosive. Instead, the lava is able to escape the central vent or rifts in the flanks of the volcano easily, then flow down the incline of the volcano.
Lava
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The type of lava erupted by Mauna Loa is basaltic lava. Basalt is the most common type of lava and it is a mafic lava. Mafic lava is hot and fluid so it is able to get to Earth's suface from the mantle, the middle layer of Earth's three layers. The mantle is the layer that contains molten rock called magma, the parent material of lava. At Mauna Loa, lava temperature has been measured as high as 2,150 degrees Farenheit (1,175 degrees Celcius). As the lava cools, it can be classified as smooth and rope-like, the flow called pahoehoe (pa-HOY-hoy), or rocky, when it's called `a`a (ah-ah).
Danger
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Mauna Loa is one of 16 Decade Volcanoes, active volcanoes that pose a risk to populations or population centers. The Decade Volcanoes program studies these volcanoes to mitigate risk to those who could be hurt by eruptions. There have been billions spent on construction on the slopes of Mauna Loa. Volcanic flows underlie part of what is now the city of Hilo.
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Resources
- Photo Credit NASA, Visible Earth-Astronaut Photograph ISS005-E-7002 through the Earth Sciences and Image Analysis Laboratory at Johnson Space Center
