Hawaii’s Mauna Loa (‘Long Mountain’) is the world’s largest active volcano.
It is one of five volcanic eruptions that made the Island of Hawaii (in the Pacific Ocean) that make up the US State of Hawaii.
It rises approximately 13,679 feet (4.169 meters) above the sea level and is about half of the island’s land mass.
According to the US Geological Survey (USGS), the volcano started to erupt Sunday night. It was the first eruption of the volcano since 1984.
The lava flows from the summit were contained early Monday morning (November 28) and didn’t threaten nearby communities.
USGS does not believe there is any risk of magma fall, but an ash fall advisory has been issued and some residents have begun to voluntarily evacuate.
The volcano’s caldera is the place where the eruption occurred.
WHY DOES MAUNA LOA Erupt?
Since 1984’s last eruption, Mauna Loa had magma under its surface. According to the USGS, Mauna Loa expands as more magma is accumulated beneath the surface.
Between August and October, geologists noted an increase in earthquakes in Mauna Loa.
Dr Jessica Johnson, a volcano geophysicist at the University of East Anglia, said it’s unclear why Mauna Loa has started erupting again now.
MailOnline explained that it could be due to a new pulse in magma or because pressure has built up over the years.
‘Monitoring data from the Hawaiian Volcano Observatory has shown that Mauna Loa has been inflating – indicating magma accumulation – for several years, and increased small earthquakes – indicating magma pushing through rocks – for several months.
“Mauna Loa” is active even though no lava is coming out of it. This is because magma is available, which could cause an eruption.
The heat moving beneath the Earth’s surface causes volcanoes to erupt. Heat is conveyed from the planet’s interior to its surface largely by convection – the transfer of heat by movement of a heated fluid.
In this case, the fluid is magma – molten or partially molten rock – which is formed by the partial melting of Earth’s mantle and crust.
The magma is raised and, in the final step of this heat-releasing process erupts on the surface via volcanoes.
Mauna Loa releases hot lava which, when it cools down, turns into basalt.
‘The Hawaiian Islands have been formed because there is a “hotspot” deep in the Earth, supplying material from the mantle that is hotter and therefore less dense than the surrounding material,’ said Dr Johnson.
“This less dense material rises from the mantle, and breaks through the crust to become volcanoes. This hotspot provides heat to all the volcanoes of Hawaii.
‘In the crust of the Earth, pockets of magma accumulate (sometimes called magma reservoirs or “chambers”).
“Some magma pockets move rapidly up to the surface to erupt. Others remain in the crust for many decades without erupting.”
HAS MAUNA LOA EERUPTED BEFORE
Mauna Loa has erupted 33 times since 1843, according to USGS – but this latest eruption marks the end of the longest eruptive pause in its recorded history.
In 1984, the most recent eruption lasted 22 days. It produced lava flows that reached within four miles (7 km) of Hilo, which is home to approximately 44,000 people.
Large, dense flows of basalt have been produced by the volcano and reached the ocean eight more times than 1868.
This new eruption is currently confined to the summit, and there is no indication that magma is moving into rift zones – areas where the volcano is rifting or splitting apart.
Mauna Loa is Kilauea’s larger neighbor. It erupted within a residential area and destroyed 700 houses in 2018.
However, Mauna Loa’s slopes can be steeper than Kilauea, so lava from eruptions can flow faster.
In just three hours, Mauna Loa’s volcanic lava traveled 15 mil (24 kms) to reach the ocean after an eruption in 1950.
Mauna Loa’s enormous size could allow it to store greater magma, which may lead to more lava flows during eruptions.
Hawaii’s volcanoes can be called shield volcanoes. The result is that successive lava flows over many thousands of years have created mountains the size of a shield.
Shield volcanoes can also be found in California, Idaho, Iceland, and the Galapagos Islands. Eight shield volcanoes can be found in Alaska’s Wrangell–St. Elias National Park, including Mount Wrangell.