Mauna Loa: The Fiery Mountain

Mauna Loa: The Fiery Mountain

Mauna Loa is Earth’s largest volcano and most massive mountain as it takes up nearly half of the flourishing landscape of the island of Hawai’i. This island is actually made up of five volcanoes, Kohala, Mauna Kea, Hualalai, Mauna Loa, and Kilauea, all in such close proximity that they fused together to form one whole island. Mauna Loa is located in the south central area of Hawai’i, in the Hawai’i Volcanoes National Park and its coordinates are 19°5' N, 155°6' W. It is 13,680 ft above sea level, but if one measures from its true base on the ocean floor, it is estimated to be 30,080 feet tall. Its name is quite fitting as it means “Tall Mountain”.

Mauna Loa is located on a hot spot in the Pacific Ocean. It is not near a plate boundary, in fact it is 3,200 km from the nearest plate boundary, and is situated in the middle of the Pacific tectonic plate. This is actually a rarity, as 90% of volcanoes are along a tectonic plate boundary. A hot spot occurs where long, stationary vertical pools of magma rise up and towards the plate. Movement of the tectonic plates above the hot spot created Mauna Loa, along with the other Hawaiian volcanoes. The older Hawaiian Islands were once above this stationary hot spot, but have been carried northwest by the slowly moving Pacific plate. As the plate moves, it carries the previously formed, older, volcanoes with it, creating a trail of younger, new volcanoes behind. The islands are lined up along the Hawaiian Ridge-Emperor Seamounts chain, which is 3,750 miles and includes Kauai, Maui, Oahu and Hawai’i, from north to south, respectively. There are around 80 volcanoes in this chain; most of them underwater, consequently the term seamount refer to submarine volcanoes. Three volcanoes of Hawai’i, Mauna Loa, Kilauea and Loihi seamount, are all currently sharing the Hawaiian hot spot. Although, recent evidence has shown that all three volcanoes use have separate plumbing systems to expel the lava from the pool of magma deep below them. It has also been suggested that Loihi is slowly moving Mauna Loa from the center of the island, thus shifting directly over the hot spot. The closer to the hot spot a volcano is, the more active it will be. The Hawaiian hot spot has laid down layers of lava, building up enormous islands from the ocean floor. Over time, the island of Hawai’i will shift away from the hot spot and make room for another, new volcanic island.

Mauna Loa is a shield volcano, with wide moderate sloping sides. Shield volcanoes are created when lava emerges out from fissures in the earth's crust. Both a'a and pahoehoe flows erupt magma, which is mafic, of low-viscosity, and the lava spreads out in thin layers. The eruptions from shield volcanoes are gentle and flow easily and are sometimes called “Hawaiian-type” eruptions.

Researchers have been studying the mineral composition on Mauna Loa for some time. They have been closely looking at its xenoliths, which are rock materials they may have been carried by lava, but not genetically related to the lava. Scientists have discovered numerous deposits of crystal-rich rocks from deep inside the volcano that were forced to the surface by volcanic eruptions. The minerals found included olivine, plagioclase, pyroxene, and combinations of all three. Some of the xenoliths are composed of minerals that are rich in magnesium and iron, while others are composed of minerals, which are rich in calcium. This indicates that the magma must have come across at least two separate chemical environments on its trek to the surface. The xenoliths also show an array of textures that show having been in different physical environments. Most of the flows of Hawaiian volcanoes, 99%, are basalt flows and erupt magma as hot as 2,200 °F. Since Mauna Loa erupts basalt flows, it magma contains around fifty percent silica and is rich in iron and magnesium. The origin of Mauna Loa’s magma is still being researched. According to a 2002 U.S. Geological Survey article, Mauna Loa has a shallow magma reservoir beneath Moku'aweoweo, Mauna Loa’s 4,000-plus foot deep caldera summit caldera, which is estimated to have collapsed over 600 years ago. The USGS website states:

Geologists must rely on data gathered from rocks at the surface of the earth, combined with geophysical information. From these data they construct a 3-D model of the many magma chambers and conduits that extend several kilometers (miles) beneath the surface of the earth.

The lush environment surrounding Mauna Loa has enthralled the native people of Hawai’i and tourists alike. Just Mauna Loa, alone, incorporates ten different zones of vegetation. As the elevation increase on the volcano, so does the desert-like climate. Mauna Loa is also one of the world’s most active volcanoes. Research indicates it has