Mauna Loa (means long mountain) is one of the five active volcanoes that form in the island of Hawaii in the Pacific Ocean. It is the largest subaerial volcano compared to the subaqueous volcano and is at an elevation of 13,679 feet. It is said to be historically the largest volcano on Earth. It forms an active shield volcano with some gentle slopes with a volume estimate of 75,000 cubic kilo metres. Its peak is about 38 metres high that is lower than its neighbour Mount Kea. This volcano has seen eruption for more than 7,00,000 years and emerged above the sea level 4,00,000 years ago.
Mauna Loa erupted after 38 years on November 27, 2022 spewing ash and debris and covered the night sky of the Hawaiian island. The eruption was so huge that night sky was covered with red light.
A volcano is a rupture or an opening in the top of Earth’s crust (mountain) through which hot lava, volcanic ash, and gases escape from the magma chamber on to the surface of Earth. On Earth, the volcanoes are associated with the tectonic plates that are diverging or converging. Most of them are even found under water like the midocean ridge, etc. There exist three main types of volcanoes such as cinder cone volcanoes, composite volcanoes, and shield volcanoes. The world’s five most active volcanoes are Sangay in Ecuador, Santa Maria in Guatemala, Stromboli in Italy, Mount Etna in Italy, and Mount Yasur in Vanuatu.
Causes of Eruption
Starting from the core of Earth, the geothermal gradient and the amount of temperature increases with increasing depth which indicates that heat forms in the deep interior of Earth, which melts the rocks and creates molten rocks, known as magma. This magma gets collected in the magma chambers which are found at a relatively shallow depth between 6 to 10 km under the surface.
This magma forces its way upwards through the cracks and fissures on Earth’s crust and is called lava.
The intensity of the eruption depends on the composition of the magma. Running magma makes less-explosive eruptions which are relatively less dangerous as gasses escape in a runny lava which leads to steady but gentle flow of lava from the mouth of the volcano. The mount Mauna Loa is one such example of less explosive eruption.
On the other hand, if the magma is thick and sticky, it makes harder for the gases to escape on a consistent basis and this builds up pressure until the breaking point is achieved. Consequently, the lava releases out with force and leads to large-scale explosion. When the lava blasts into air, it breaks into small pieces called tephra which can range from tiny pieces to large boulders. This type of explosion is dangerous and is typically seen in strombolian type of volcanic eruption. The most dangerous type of eruption is called a ‘glowing avalanche’ when freshly erupted magma flows down the sides of a volcano, and can travel quickly and reach temperature of up to 1200 degrees Fahrenheit.
This sort of eruption is dangerous as thick clouds of tephra race down quickly and can destroy everything in its path. If it is thick enough, the blanket of ash can suffocate the humans, plants, and animals. If the volcanic matter mixes with nearby water sources, it can lead to create mud flows which can bury the entire community.
The current Volcanic Explosivity Index (VEI) rating of Mauna Loa is not known. The VEI is a measure of explosiveness of volcanic eruptions.
About Mauna Loa
The Mount Mauna Loa is an active shield volcano having relatively gentle slopes. It is the largest active volcano on the planet. It is about 4,169 metre above the sea level and makes up half of the island of Hawaii area of about 5,271 sq. km. Its dome is 129 km long and 103 km wide. Mauna Loa has erupted some three dozen times since the first documented eruption in 1843. Many of the eruptions are confined within Mokuaweoweo Caldera. Mauna Loa is about 7,00,000 to 1 million years old and is formed by repeated fluid lava flows.
The earliest eruptions flew onto the seafloor between about 0.6 and 1 million years ago. It emerged above sea level around 3,00,000 years ago, and has rapidly grown since then. The summit area of the volcano is above the 12,000 feet. At least 33 radial vents have been mapped by geologists on the north and west sectors of the volcano.
Significance of Mauna Loa Eruptions
According to native Hawaiian community, volcanic eruption of Mauna Loa carries a larger cultural and political significance and a message to respect indigenous communities and land. Many Hawaiians draw from their mythology around Pele, the Hawaiian goddess of fire and creator of the islands. Some assert that the auspicious timing of the eruption is no coincidence but symbolises an ‘affirmation’ of the community’s cultural practices and independence from colonial forces.
Pele’s symbolism is also significant in the context of the Hawaiian Independence Day, the Anglo-Franco Proclamation of 1843. According to experts, the US illegally overthrew the Kingdom of Hawaii 50 years after independence. American colonialism is marked with military occupation on the islands.
Eruptions of Mauna Loa in the Past
According to data provided by an official Website of the US government, usgs.gov, Mauna Loa’s Northeast Rift Zone has erupted eight times since the mid-19th century—in 1843, 1852, 1855–56, 1880–1881, 1899, 1935–36, 1942, and 1984. Mauna Loa typically erupts lava at a very high rate, combined with the steep slopes of Mauna, resulting in long travelled-flows, within 4 miles of the District of Hilo, which has been threatened by seven Mauna Loa flows.
Volcano Alert Levels and Aviation Colour Codes
There is a standardised alert-notification system for people on the ground and in the air (aviation). As for alert levels, ‘Normal’ indicates a non-eruptive state of a volcano. ‘Advisory’ indicates exhibiting signs of unrest above known background level. It does not mean that an eruption is likely or certain. ‘Watch’ indicates heightened or escalating unrest with increased potential of eruption. An eruption is likely underway with limited hazards. ‘Warning’ shows that a hazardous eruption is suspected to be occurring, though visual observation cannot verify the eruption to be in progress.
The colours for the above-mentioned four levels of normal, advisory, watch, and warning are green, yellow, orange, and red, respectively.
Impacts of Eruption
Volcanic eruption poses several hazards like volcanic ash, gases, lahars, landslides, lava flows, and pyroclastic flows.
Lava is one of the health hazards and poses risk to life and property as molten rocks could cover houses, farms, and neighbourhoods and often causes population displacement and food shortage. Sulphur-rich and other volcanic gases such as smog or vog also pose risk to health. The vog can cause burning in the eyes, headache, and sore throats. As per the US Geological Survey data, Mauna Loa released about 15,000 tonnes of carbon dioxide during its 1984 eruption. If lava flows in voluminous quantity, the current eruption can prove to be highly dangerous.
Due to the continuous volcanic eruptions, this volcano has undergone rift formation due to a series of earthquakes. The rift zones spread and it becomes easier for magma to emerge.
Volcanic eruptions cause landslide and mudslides, which are dangerous. Ash fall from eruption can damage buildings and vehicles, contaminate water supply, disrupt sewage, and electricity systems, etc.
However, volcanoes provide a number of environmental benefits such as fertile soils, hydrothermal energy, precious minerals, and tourism.
Terms related to Volcanic Eruption
Tephra are fragments of volcanic rock less than 2 millimetres to more than 1 metre in diameter that blast into the air during an explosive eruption.
Ash fall is a fine component of tephra that spreads over broad areas during an eruption. Ash particles can be hard, abrasive, and mildly corrosive. Freshly fallen ash can have an acidic coating that irritates eyes and lungs, and may pollute local water supplies and damage vegetation.
Lahar (mud or debris flows) is an Indonesian term which means hot or cold mixture of water and volcanic debris flowing down the slopes of volcano, and often entering a river valley. Lahars vary in size and speed and may be a few metres wide and several centimetres deep or hundreds of metres wide (up to 10 metres in diameter) and tens of metres deep.
Lava flows are streams of molten rocks that pour or ooze from an erupting vent. Fluid basalt flows can extend tens of kilometres and travel 1 kilometre per hour on gentle slopes and up to 10 kilometres per hour on steep slopes.
Volcanic gases released from a volcano include steam, carbon dioxide, sulphur dioxide, hydrogen chloride and hydrogen fluoride.
Pyroclastic flows and surges are high-density mixtures of hot, dry rock fragments and gases that move away from the vent at high speed. It consists of a basal layer of coarse fragments that move along the grounds and a more buoyant upper layer. This flow can deposit layers ranging from less than 1 metre to more than 200 metres.
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