Making an explosive double date with Russian volcanoes

Kamchatka is one of the most volcanically active places on Earth. It is part of the Ring of Fire -- intermittent chains of volcanoes that encircle the Pacific Ocean. Over at least the last 6 million years, Kamchatka has experienced more explosive eruptions than any place on Earth. Historically, the level of activity has made it difficult for people to explore its interior. The region boasts a wealth of volcanic features and is rapidly, sometimes explosively, changing. This makes Kamchatka a unique site for studying how volcanic cycles shaped the landscape of the early Earth.

Dr Agnes Samper (University of Quebec, Montreal, Canada) and Dr Pierre Lahitte (University of Paris-Sud, Orsay, France) are travelling to Kamchatka, located in the far north-east of Russia, to investigate the Mutnovsky and Gorely volcanoes.

The expedition, which runs from August 24th to September 7th, is part of the Europlanet Research Infrastructure's Transnational Access Programme. The international team includes Russian volcanologist, Dmitry Melnikov, of the Kamchatka Volcanic Eruption Response Team and four scientists from the Space Research Institute in Moscow with Nadia Evdokimova as coordinator of the transnational expedition.

The Mutnovsky and Gorely volcanoes are separated by just 15 km. They have been volcanically active for 700 000 -- 800 000 years and they have both gone through a succession of building and destructive episodes. The Gorely volcano was entirely destroyed in an explosive eruption, leaving only a large depression known as the Gorely caldera. Since then, activity has renewed and upcoming magma has filled the caldera to build the present volcano.

"The date of the big destructive event that initiated the new Gorely is something of a mystery. Previous studies using other techniques have given contradictory ages. Gorely has been through three cycles of being built up and then destroyed in massive explosions and Mutnovsky has been through four. We will be using dating techniques based on natural radioactive decay to pin down accurate ages for these events that have built Mutnosvky and Gorely into the volcanoes that we see today," said Dr Samper.

The team will collect samples from lava flows around the site and take them back to their laboratories in Orsay and Montreal for radioactive dating. Samples will be tested for levels of radioactive potassium, which is found in minerals in the rock and decays over 1.25 billion years into the noble gas Argon, which becomes trapped in the crystalline structure of the rock.

So far, radioactive dating for this area has measured carbon-14 in coal formed from vegetation burnt by lava during eruptions. This only allows us to study the past 40 000 years. By measuring potassium and argon, we can work directly with the volcanic rocks, giving us the age of the lava the moment it reached the surface -- thus the date of the eruption. Our technique has proved to be suitable for very young rocks and can be used to date rocks back in time up to the formation of the Earth," said Dr Samper.

During the two-week trip, the team will be hiking on foot to find fresh, unweathered samples of lava flows from the slopes, tops, and foothills of any mains stages of both volcanoes. By collecting samples from river channels that cut deep across the oldest basal deposits, the team will access rocks that are usually buried.

"We will need to sample 2 to 3 kg of rock for each site that we wish to date, which promises heavy backpacks to bring back to the camp every night! But we are confident that the long and strenuous hikes will not curb our enthusiasm to understand the complexity of the fascinating stories of Gorely and Mutnovsky volcanoes," said Dr Samper.