Here’s the science behind Mauna Loa’s volcanic eruption

Hawaii’s Mauna Loa, the world’s largest active volcano, has erupted luminous rock fountains and the eruption of lava from the fissure was the first eruption almost forty years Started on November 27, 2022.

Where does all this lava come from?

We asked Gabi LaskeA geophysicist at the University of California, San Diego, who led one of the first projects to map the underground plumbing that feeds the volcanoes of the Hawaiian Islands.

Where does the magma in Mauna Loa come from?

The magma that erupts from Mauna Loa originates from several magma chambers located 1 to 25 miles (2 to 40 km) below the surface. These magma chambers are only temporary repositories of magma and gas, not where the magma originally formed.

The origins are deeper Earth mantle, perhaps 620 miles (1,000 km) deeper. Some scientists believe that magma is derived from a 1,800 miles (2,900 km) deepwhere the mantle meets the Earth’s core.

Here’s an example of what a Hawaiian mantle plume might look like. Joel E. Robinson/USGS

The Earth’s crust is made up of tectonic plates that slowly move at the same rate as fingernails grow. Volcanoes are usually formed when these plates move away from each other or when one is pushed under the other. But volcanoes, like those in Hawaii, can exist between plates In the Pacific plate.

The crust and mantle that make up the Pacific Plate break apart at different places as it moves northwest. Beneath Hawaii, magma can move up through cracks to feed various volcanoes on the surface. The same thing happens at Haleakala in Maui. last time it exploded About 250 years ago.

How does molten rock move from deep in Earth’s mantle, and what exactly is a mantle plume?

Scientists hypothesize that the mantle is not made of uniform rock. Instead, difference in type mantle rocks melt different temperatures. Mantle rocks are solid in some places and melt in others.

Partially molten rock floats and rises to the surface. Ascending mantle rocks form mantle plumes. As the rock rises, the pressure in its stratum decreases, so it melts more and eventually accumulates in the magma chamber. If there is a large enough vent to the surface and enough volcanic gas has accumulated in the magma chamber, the magma will be pushed to the surface by a volcanic eruption.

Seismic imaging shows that the Earth's cross-section shows two possible sources for the mantle plume, one that starts deeper and flows along a tortuous path.

The origin of the magma may be more than 620 miles deep, and some scientists speculate that it may originate as deep as 1,800 miles where the mantle meets the Earth’s core. Gabi Laske

Seismic mapping by the research teams I work with has shown the presence of the Hawaiian mantle plume. comes from deep in the mantle.

But some conceptual data show that the plume is not a straight tube. Instead, there is twists and turns, initially from the southeast, but then turns westward over Hawaii as the plume enters the shallow mantle. Rifts in the Pacific Plate then funnel magma into the magma chamber beneath Hawaii Island.

Why do Hawaii have less violent eruptions than other places?

Hawaii is in the middle of an oceanic plate. In fact, it is the world’s most isolated volcanic hotspot, far from any plate boundaries.

Oceanic magma is very different from continental magma. It has a different chemistry and flows more easily. So it is called magma less prone to clogging vents On its way up, it will eventually lead to more explosive volcanoes.

A thermal image shows the eruption of Mauna Loa on November 27, 2022, which began around 11:30 p.m. Temperature is in degrees Celsius. USGS.

How do scientists know what’s going on below the surface?

Volcanic activity is monitored using a variety of instruments.

Perhaps the easiest to understand is GPS. The way scientists use GPS is different from everyday life. It can detect movements as small as a few centimeters. Any upward movement on the surface detected by GPS in a volcano indicates that something is pushing from below.

Even more sensitive inclinometer, which is essentially the same as the bubble level that people use to hang pictures on their walls. Any change in the tilt of the volcano’s slope indicates that the volcano is “breathing” again, as magma is moving underneath.

Map of Hawaii showing Mauna Loa and lava flow paths since the late 1800s.  There have been several explosions, and they tend to go both ways.

A very important tool is the observation of seismic activity.

Volcanoes like Hawaii are monitored by a large network of seismographs. Any movement of the magma below causes tremors seismometer. A few weeks before Mauna Loa erupted, scientists noticed tremors coming from increasingly shallow depths, indicating rising magma and an imminent eruption. This allowed scientists to warn the public.

Other ways to monitor volcanic activity include chemical analysis of the gases released through fumaroles – vents and fissures through which volcanic gases escape. If the composition changes or the activity increases, this is a clear indication that the volcano is changing.

This article has been republished Talk Under Creative Commons license. Read the original article.


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