Last updated January 24, 2018 at 2:24 pm
Small crystals found in lava may hold the key to understanding how volcanoes will behave in future.
The changing composition and growth of crystals as they move upwards through a volcano are recorded in layers, which can be read like the growth rings on a tree.
A new study suggests that the history from these layers, as they grow in magma and rise from depths of around 30 kilometres to the surface of the Earth, may help scientists monitor volcanoes more effectively – even dormant ones.
Crystals formed in the run-up to a volcanic event can provide evidence of processes leading to and timing of eruptions.
Arrival of new magma is eruption trigger
“They essentially ‘record’ the processes right before the eruption starts,” says Dr Teresa Ubide from the University of Queensland, the lead author of a new study.
While the arrival of new magma into an existing reservoir is a common eruption trigger, the time between the two events can vary from a matter of days to years.
By studying the crystal record of past eruptions, the new study seeks to provide better understanding of the recharge mechanisms, as well as the pathways and timescales involved, to improve eruption forecasting at individual volcanoes.
Ubide and her colleague Professor Balz Kamber from Trinity College Dublin, used a laser technique to examine the insides of these crystals in Sicily’s Mount Etna, Europe’s most active volcano.
They analysed 287 clinopyroxene crystals in Mt Etna lavas from 40 years of eruptions from 1974 to 2014, collected from different vents, noting the recharge to eruption timescales of the crystals.
Trying to decode eruption-triggering mechanisms
“At Mount Etna, we found that the arrival of new magma at around 10 kilometres depth is a very efficient trigger of eruptions – and within only two weeks,” she says.
Earth tremors at the depth of the magma chamber being recharged might be signs of potential imminent eruptions, Ubide says.
“At other volcanoes, the method will allow to establish the relationship between recharge depth, recharge frequency and eruption efficiency.
“This can then help scientists to better relate physical signs of recharge to eruption potential.”
Given that clinopyroxene is a common crystal in many volcanic lavas, Ubide and her team are planning to expand the study to other volcanoes around the world, and to combine the information with signs of magma movement.
“Combined with better constraints on crystal growth rates, such studies have potential to help decode eruption-triggering mechanisms, depths and timescales,” they write in the study.
Predicting eruptions in dormant volcanoes
“Improved constraints on the movement of magma preceding past eruptions could advise future volcano monitoring efforts in relation to the origin of seismic or deformation signals and the time available for hazard evaluation and emergency planning.”
Kamber believes the new approach may also prove useful for studying volcanoes that have remained dormant for long periods, leaving scientists with little eruption history.
The currently erupting volcano on Kadovar Island, Papua New Guinea, for example, is proving difficult to predict for this very reason.
“For many volcanoes there is no eruption history, but geologists can collect lavas from past eruptions and study their crystals,” Kamber says.
The findings have been published in the journal Nature Communications.