Mauna Loa

Panorama of the Mauna Loa

The Mauna Loa is one of the largest active volcanoes in the world and is located in the Pacific on the main island of the archipelago of Hawaii.

Name

The name Mauna Loa Hawaiian means: long mountain, which is explained by its from NNE to SSW elongated shape.

Location

The shield volcano occupies a large part of Hawaii, the largest island of the Hawaiian archipelago, a.

Most important data

The mountain rises to 4170 m, but also reaches 5000 m up to its submarine base into the sea down, if you still see this involves the assumption that has been lowered by the weight of the mountain to the ocean floor at about 8000 m, could be found on a theoretical total height of 17,000 m come ..

Its length is about 120 km. It covers 5270 km ² and has a volume of about 80,000 km3.

Structure of the volcano

It is an elongated shield volcano with a summit caldera, which measures 3x5 km and has a depth of 183 m. This caldera is probably 600 BC - 750 years collapsed, in an older, 6x8 km caldera. Mauna Loa is currently in the second construction stage of volcanic ocean islands, the shield stage. The lower part of the volcano is old to about one million years, dating from the first construction stage, the Seamountstadium. This lower portion is identified by pillow lava and Hyaloklastiten, the upper part mainly by Tholeiitbasalten of low viscosity.

Like many large volcanoes are also located on Mauna Loa volcano columns that are responsible for the elongated shape of the volcano building in this case. Here are two axial rift zones that extend from the summit crater Mokuaweoweo. Each of them contains magma -filled columns.

Eruption history

It is believed that the first eruption occurred in the system 1000000-700000 years ago. 400,000 years ago estimated the volcano has overcome the seamount stage and produced lava and tephra, but the oldest actually been clearly datable rocks have an age of about 200,000 years ..

Little is of outbreaks during the period of pure Polynesian settlement known. From the year 1832 has the report of a missionary of an outbreak of Mauna Loa, however, the rapporteur was on the neighboring island of Maui, about 190 km away.

Since then, we know of at least 33 eruptions of Mauna Loa to the last date of 1984, 17 eruptions in the 19th century and 15 in the 20th century. An eruption in the 19th century took a whole year, from August 1871 to August 1872. A total of 4.1 km3 of lavas were produced.

The series of eruptions in 1950

This is about the most spectacular eruption of Mauna Loa volcano in historical time.

The outbreak focused on the southwestern flank of the mountain, with a 20 km long eruption column moved across the rift zone. The eruptions followed the established on the Mauna Loa rhythm, with a summit eruption draws a flank eruption after usually after about 1-2 years.

Although the eruption sites were at an altitude of about 3,200 m above the sea, reached the lavas of this in less than 4 hours. Numerous lava flows made ​​over the course of the eruption of staggered columns arranged, but the damage was relatively low. The aa lavas of the lava flow streamed at a rate of up to 48 km / h valley. Particularly spectacular is the influx of these lavas was into the sea.

During the 23 days of ongoing eruptions, the volcano had finally produced 376 million cubic meters of lava, where it is the largest known outbreak with the outflow rate in Hawaii.

The outbreak in 1984

Since the outbreak series of 1975 it had been found growing bulge in the volcano Mauna Loa. To this end, joined in the spring of 1984, earthquake swarms, of which the deepest located earthquakes were located at 13 km and reached the strongest a magnitude of 6.6. The tactics involved the intrusion of dykes. Shortly before the start of the eruptions on 24 March 1984, the number of micro-earthquakes and Volcanic tremors increased set in, so that one sensitive telescopes could not keep quiet on the 42 km distant Mauna Kea.

On March 25, the actual outbreaks translated first into lava fountains in the southwest of the summit caldera. After 2-3 hours, much of the caldera was covered with lava. In the late afternoon, the activity on the northeast rift zone shifted approximately 650 m below the summit.

In the next few days, the lava flows threatened the city of Hilo, but stopped at the edge of the same, because the lava was eventually distributed by means of perforation of levees on a wide slope area and no longer channeled streamed in a few channels. Moreover, had by cooling its viscosity increases ( AA lava), the slope in front of the city was low and growth slowed the lava flows. On April 15, the outbreak series was finished ..

Development in 2007 and situation 2012

According to the Hawaiian Volcano Observatory 2007, the following developments were observed in:

Since the beginning of July 2004, an increasing number of volcanic tremors were registered in the depth of Mauna Loa. The number of earthquakes fluctuated from week to week, but was higher than normal. Alone in the first week of September of 2004, there were more than 350 earthquakes in 35 to 50 km depth. It was this to be long-period earthquakes, whose shock waves gradually emerge from the seismic background. This was not happened since records began in 1960.

The publication of a geophysical study led in May 2007 to a strong media coverage. Some messages aroused thereby the impression that an outbreak would be imminent shortly. The Hawaiian Volcano Observatory noted in a report on May 21 that there were no significant changes.

How many calderas, such as Campi Flegrei or Askja, Mauna Loa seems to "breathe". So you put directly determined by the series of eruptions of 1984 an incipient bulge, but then returned for several years into its opposite. It was not until 2002, the volcano began to aufzuwölben again, but this was slowed down to 2009 again. Since 2010, only a very slow bulge can be observed.

In the fall of 2012, the volcano proves to be quiet. No significant bulge was found and only a few shallow earthquakes, no striking gas emissions.

Hot Spot

Mauna Loa, and other volcanoes in Hawaii, Mauna Kea, Hualālai and Kīlauea are developed over a hot spot. Hot spots are areas where transport from the deep mantle rising hot Aufströme called Plumes, material up to the surface. In the case of Hawaii, the region is pushed on the Pacific lithospheric plate by plate tectonics slowly over the hot spot, which at a distance of millions of years a whole chain of volcanic islands and seamounts, which was Hawaii - Emperor chain of islands formed up from the Aleutian Islands extends into the middle of the Pacific.

It has this theory used to explain the different composition of lavas from Mauna Loa in comparison with those of Mauna Kea. The tholeiitic basalts of Mauna Loa, a volcano that is in a stage of the shield assembly, therefore, are a result of a position directly above the hot spot. Has reached Whereas Mauna Kea already in the next stage, is no longer directly over the hot spot, and produces basalts of alkaline series. Some researchers explained this with the chemical composition, different zones of the mantle from which the magma would come, others with different zoning of the ascending mantle plumes.

Studies on the vegetation on the volcano Mauna Loa

In 1997, studies were conducted at six different sites for the growth of iron woods at Mauna Loa, a flowering shrub that is similar to the rhododendron and is typical of the Pacific. They wanted to test different growing conditions, especially the influence of altitude and temperature. As might be expected turned out that the resident in lower layers plants ( about 700 m) better headway than in 1600 m height. However, seems interesting that Mauna Loa for some reason felt for such tests to be particularly suitable: Due to the isolated location thrives on the islands, only a limited number of species. In addition, exist on the shield volcano lava flows that cover many areas of air, so that a very homogeneous picture of the soil results.

Myths and legends about Mauna Loa

The volcano goddess Pele will one day be gone incognito with Poliahu, the snow goddess of Mauna Kea, a sled race. But suddenly fire leaped from the earth and Poliahu recognized her enemy Pele.

The locals believe that the goddess Pele sends a white dog in front of an eruption, the slopes of the mountain down to the people, to warn them.

Observatories on Mauna Loa

On the Mauna Loa are the Mauna Loa station, a meteorological station, which is mainly specialized in carbon dioxide measurements, as well as an observatory.