The Mauna Loa : Biggest Mouth Of Earth

Mauna Loa Eruption

Overview: Mauna loa is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaiʻi in the Pacific Ocean. The largest subaerial volcano in both mass and volume, Mauna Loa has historically been considered the largest volcano on Earth, dwarfed only by Tamu Massif. It is an active shield volcano with relatively gentle slopes, with a volume estimated at approximately 18,000 cubic miles (75,000 km3),[4] although its peak is about 120 feet (37 m) lower than that of its neighbor, Mauna Kea. Lava eruptions from Mauna Loa are silica-poor and very fluid, and they tend to be non-explosive.

Mauna Loa has probably been erupting for at least 700,000 years, and may have emerged above sea level about 400,000 years ago. The oldest-known dated rocks are not older than 200,000 years. The volcano's magma comes from the Hawaii hotspot, which has been responsible for the creation of the Hawaiian island chain over tens of millions of years. The slow drift of the Pacific Plate will eventually carry Mauna Loa away from the hotspot within 500,000 to one million years from now, at which point it will become extinct.

Geology: Like all Hawaiian volcanoes, Mauna Loa was created as the Pacific tectonic plate moved over the Hawaiian hotspot in the Earth's underlying mantle. The

Hawaii island volcanoes are the most recent evidence of this process that, over 70 million years, has created the 3,700 mi (6,000 km)-long Hawaiian–Emperor seamount chain. The prevailing view states that the hotspot has been largely stationary within the planet's mantle for much, if not all of the Cenozoic Era. However, while the Hawaiian mantle plume is well understood and extensively studied, the nature of hotspots themselves remains fairly enigmatic.

Structure: Mauna Loa is the largest subaerial and second largest overall volcano in the world (behind Tamu Massif, covering a land area of 5,271 km2 (2,035 sq mi) and spans a maximum width of 120 km (75 mi). Consisting of approximately 65,000 to 80,000 km3 (15,600 to 19,200 cu mi) of solid rock, it makes up more than half of the surface area of the island of Hawaiʻi.

Combining the volcano's extensive submarine flanks (5,000 m (16,400 ft) to the sea floor) and 4,170 m (13,680 ft) subaerial height, Mauna Loa rises 9,170 m (30,085 ft) from base to summit, greater than the 8,848 m or 29,029 ft elevation of Mount Everest from sea level to its summit. In addition, much of the mountain is invisible even underwater: its mass depresses the crust beneath it by another 8 km (5 mi), in the shape of an inverse mountain, meaning the total height of Mauna Loa from the start of its eruptive history is about 17,170 m (56,000 ft).

Eruotive History: The oldest exposed flows on Mauna Loa are thought to be the Ninole Hills on its southern flank, subaerial basalt rock dating back approximately 100 to 200 thousand years. They form a terrace against which younger flows have since banked, heavily eroded and incised against its slope in terms of direction; this is believed to be the result of a period of erosion because of a change in the direction of lava flow caused by the volcano's prehistoric slump. These are followed by two units of lava flows separated by an intervening ash layer known as the Pāhala ash layer: the older Kahuka basalt, sparsely exposed on the lower southwest rift, and the younger and far more widespread Kaʻu basalt, which appear more widely on the volcano. The Pāhala ashes themselves were produced over a long period of time circa 13 to 30 thousand years ago, although heavy vitrification and interactions with post and pre- creation flows has hindered exact dating. Their age roughly corresponding with the glaciation of Mauna Loa during the last ice age, raising the distinct possibility that it is the product of phreatomagmatic interaction between the long-gone glaciers and Mauna Loa's eruptive activities.

Possible eruptions occurred around 1730 and 1750 and sometime during 1780 and 1803. A June 1832 eruption was witnessed by a missionary on Maui, but the 190 km (118 mi) between the two islands and lack of apparent geological evidence have cast this testimony in doubt. Thus the first entirely confirmed historically witnessed eruption was a January 1843 event; since that time Mauna Loa has erupted 32 times.