IT USED to be that no self-respecting visitor to Azerbaijan would leave without wallowing in the gooey, supposedly health-giving effluent of a mud volcano. The country鈥檚 tourist industry still makes great play of them, since Azerbaijan boasts nearly half of the world鈥檚 800 known mud volcanoes, though thousands more could be bubbling away undiscovered on the ocean floor.
What do mud volcanoes have in common with their lava-spewing cousins? We know less about them, perhaps because they aren鈥檛 so dramatic and glamorous. Small cones of mud and clay, they are usually under 2 metres tall, though some in Azerbaijan reach heights of 400 metres. The mud forms from hot water and fine sediment as deep as 10 kilometres underground, and either pours gently from a vent in the ground or is ejected into the air as a fountain.
How often do mud volcanoes erupt? In Azerbaijan it happens three to five times a year, though lately things have been hotting up, according to Adil Aliyev, head of the Laboratory of Mud Volcanism at the Geology Institute of the Azerbaijan National Academy of Sciences in Baku. 2001 was an exceptional year, with 18 eruptions. Baku residents were treated to the spectacle of one mud volcano, 15 kilometres from the city, spurting flames high into the air and depositing a thick layer of mud over the surrounding area. The next three years were quieter, but since 2004 things have started getting busy again.
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What is triggering this frenzy of activity? Scientists are desperate to know, partly because they think there may be a link between mud volcanoes and earthquakes. While eruptions are more likely to occur after an earthquake, Aliyev says the composition of gases the volcano emits changes in the period before an earthquake. Specifically, the concentrations of helium and carbon dioxide increase, a finding that could possibly be used to predict earthquakes, although researchers will have to learn a lot more about the complex plumbing of mud volcanoes first. One major puzzle is how the mud is forced up to the surface from the depths of the Earth鈥檚 crust. One theory is that, like magma, it accumulates in intermediate structures a few kilometres down, but so far no one has found these so-called 鈥渕ud chambers鈥�.
鈥淢ud can pour gently out or be ejected into the air as a fountain鈥�
There is another reason for researchers to be interested. Mud volcanoes are often found above oil reservoirs, and their plumbing offers prospectors an easy way down. They are also found close to methane seeps. Mud volcanoes could be a lot more valuable to Azerbaijan鈥檚 economy than their unglamorous appearance suggests.
