Scientists discover patterns in growth, showing that Volcanoes have a circle of life
Shortly after volcanoes collapse, they begin to regenerate again. Scientists have reconstructed the process by collecting volcanic data from more than six decades. The new knowledge could minimise casualties from future eruptions.
Darkness fell several hours ago, but the sand on the Indonesian beach of Tanjung Lsung is still warm. Music is coming from a stage right on the water’s edge, where a pop-rock band called Seventeen is playing. There is no warning whatsoever as a high wall of water roars suddenly from the ocean, sweeping away everything on the beach and crashing into the palm tree beyond. When the sun rises the next morning, 22 December 2018, more than 420 people have been killed among the ruins of small tourist towns up and down the coast. Among the musicians from Seventeen, only the lead singer survives.
Tsunamis can be terrifying events. Only last month New Zealand sent out tsunami alerts after off-shore earthquakes, and many readers will remember the 2004 Boxing Day tsunami and the inconceivable devastation it left behind. But the cause of the wave that engulfed Tanjung Lsung was no earthquake. It was caused by a sudden massive slide of material pouring down the sides of the island volcano Anak Krakatau as it began to erupt, striking the ocean with massive force, raising a tsunami which then headed towards the closest shores.
Predicting such disasters is notoriously difficult. But a team of scientists is hoping that more than 60 years of data from previous volcanic collapses will help them better
understand both volcano collapses and the way they reconstruct themselves afterwards, so that natural disasters like the one on Tanjung Lsung beach can be predicted, and loss of life greatly reduced.
Volcano reveals its life cycle
The collapse of Anak Krakatau is just one of many ways in which volcanoes can present danger to their surroundings as pressure from magma increases. Scientists are constantly improving their ability to interpret small earthquakes, gas leaks and altitude changes of Earth’s crust – characteristics that contribute to an overall impression of a mountain on the edge of a breakdown. Yet the exact moment of an eruption remains hard to predict, and often the devastation still takes local communities by surprise.
One area now being studied is the full cycle through which many volcanoes go. After an eruption that spews one side of the mountain into the ocean, or destroys the volcano cone completely, there is a period of reconstruction that may take hundreds or thousands of years before
the volcano is once again ready to blow. Russian and German scientists – headed by geologist Alina Shevchenko from the Helmholtz Center in Postam, Germany – have now studied for the first time how a volcano reconstructs its cone from scratch.
Bezymianny, located on the Kamchatka Peninsula to the far east of the Asian continent, is around three kilometres high. Until the 1950s it had been considered extinct, but since a dramatic eruption in 1956 it has been one of the world’s most active volcanoes. (Its immediate neighbour, Kluchevskaya Sopka, made international news in March with a large eruption forming a new cone on its north-western flank.) Bezymianny is one of 15 ‘lab volcanoes’ around the world which are monitored particularly closely by scientists, along with some of its most famous peers – Etna, Vesuvius, Mount St. Helens, and Fujiyama.
Two lava domes emerged
When Bezymianny blew up in 1956, the entire eastern side of the volcano disappeared, removing some 700,000m of rock. But the mountain began to rebuild remarkably quickly. According to scientists, so much of the volcano has been recreated in the decades since the original explosion that the Bezymianny should regain the size and height it had in 1956 within another 10-15 years – probably then ready for another large eruption. So in just 80 years it will have completed a full life cycle – many times faster than the average volcano.
Alina Shevchenko and her colleagues have meticulously analysed all available data from Bezymianny. They had access to a large archive of photos and data from Soviet and pre-Soviet times, and by adding more recent satellite photos, the scientists were able to recreate a highly detailed lifecycle of this active volcano.
The scientists understood the process by which Bezymianny began to build a new cone so quickly. Two deep volcanic conduits some 400 metres apart supplied a flow of magma which produced two lava domes. Towards the mid-1970s, these domes grew larger as the pipes moved, reducing the distance between them to 200 metres. Eruptions were becoming ever more violent, with material being thrown over ever further distances.
Shortly before 2000, the two pipes became connected, forming a central crater pipe surrounded by an almost symmetrical volcano cone, as had existed before 1956. The scientists’ studies also reveal that alternating layers of ash and lava have stabilised Bezymianny’s new cone.
Together with data from the nearby Shiveluch volcano, which is unable to build a new cone, the results have provided the team with improved knowledge of when volcanoes are stable and when they are weak, and that will be useful in predicting a flank collapse like those of Bezymianny in 1956 and Anak Krakatau in 2018. Flank collapses, where an entire side slides, have historically been highly lethal, especially where the rock ends up in the ocean and triggers a tsunami. The very name ‘Anak Krakatau’ means ‘child of Krakatou’, indicating how the volcano had reconstructed itself since 1883, when the original volcano famously erupted in an explosion so loud it was heard in Perth, Western Australia. Some 36,000 people were killed in 1883, mainly from the resulting tsunami. Anak Krakatau rose above the waves as a new island after fresh activity at the end of 1928.
New knowledge used in Hawaii
There are other volcanoes with flanks that might collapse. Scientists are closely monitoring Kilauea on the south-east coast of Hawaii. It barely reaches above the water, but beneath the waves the volcano is massive, and unstable. The southern flank – known as Hilina Slump – is already sliding down at a slow speed of about 10cm a year. Scientists fear that pressure from gravity and new magma will suddenly accelerate the slide, causing the flanks to collapse.
A flank collapse from Kilauea would deliver a huge threat to Hawaii, though beyond those islands other land masses are so distant that the energy of a tsunami would be spread across a very large area. Calculations indicate that waves striking the main American coast could be as low as one metre high, or as high as five metres.
But there are other volcanoes under threat of flank collapse, and some of these are located far closer to densely populated areas of our planet. One of these is Mount Teide, nestled in its crater atop the Canary Island of Tenerife, where a tsunami could devastate coastal areas of North-Western Africa and Europe.
The improved insight into the interior life-cycle of volcanoes is vital information for upwards of 500 million people who live in the shadow of these energetic mountains. In good times, local residents benefit from their volcanic neighbours, which contribute fertile farmland, warm water, and thermal energy. But the price is a constant threat of violently destructive eruption. Any new information which improves the ability of scientists to predict disasters in advance could be a real life-saver.