(ORDO NEWS) — Kilauea volcano in Hawaii is considered the most active volcano in the world, but we still don’t know how it was born.
New research shows that the original magma womb lies more than 90 kilometers below the hotspot. Although previous studies found two shallow chambers of magma beneath Kilauea, they were not large enough to account for the volume of liquid rock erupting from the volcano.
A larger chamber, about 11 kilometers (that’s 6.8 miles) deep, was discovered using seismic waves in 2014, but now it looks like the original magma chamber is even deeper.
A new analysis of broken fragments of ancient volcanic rock recovered from the southeast flank of the Big Island shows that Kilauea was born from a pool of pyroclastic material about 100 kilometers deep.
Sometime between 210,000 and 280,000 years ago, the Pacific tectonic plate shifted and a plume of magma rushed up into the sea. As the hot liquid cooled and solidified, it formed a large “shield” that broke through the waves about 100,000 years ago.
This is how Kilauea came into being, but the original rocks ejected from this hotspot are incredibly hard to find, as they are buried under numerous layers of newer lava. The igenic rocks recovered in this study provide an unparalleled glimpse into the volcano’s deep and distant past.
It was previously thought that the Kilauea volcano was formed as a result of the partial melting of solid rock under the influence of the heat of a hot spot.
The new study, however, finds no evidence to support this hypothesis. In the collected rocks, a set of rare earth elements was found, which, according to the models, could be formed in only one specific way.
It appears that instead of partial melting, Kilauea Volcano was originally formed by fractional crystallization. This term describes the formation of crystals in deep magma pools that do not subsequently react with the residual melt.
“We have studied the formation of these samples through experimental work involving the melting of synthetic rocks at high temperatures (> 1100 ˚C) and pressures (> 3 GPa), as well as through a new method for modeling the concentration of rare earth elements,” explains lead author of the study. , geologist Laura Miller from Monash University in Australia.
“We found that the samples could only have been formed by crystallization and removal (fractional crystallization) of the garnet.”
Garnet is a crystal that can form when magma is subjected to high pressure and temperature more than 90 kilometers below the earth’s crust. The fact that its presence is necessary to explain the composition of the Kilauea rocks suggests that the original eruption came from the same depth.
Or perhaps even deeper. Experiments show that garnet can crystallize up to 150 kilometers below the earth’s crust.
The Hawaiian origin may not be as deep, but new evidence suggests that the Kilauea aqueduct is not as shallow as we once thought.
“This disproves the current view that fractional crystallization is an exceptionally shallow process and suggests that the development of a deep (>90 km) magma chamber is an important early stage in the birth of a Hawaiian volcano,” says Miller.
Other volcanoes in other parts of the world, such as Mount Vesuvius, also show crystal formation times, suggesting “long-lived, deep-seated” magma reservoirs lurking below the surface. However, Kilauea’s original magma chamber appears to be much deeper than most.
Why this is so remains a mystery.
Contact us: [email protected]