19/01/2015 Scientists intrigued by a unique volcano on the ocean floor

Methane bubbles from Haakon Mosby mud volcano. Photo: Alfred Wegener Institut

Norway has two active volcanoes. One is the northernmost subaerial volcano in the world, Beerenberg on the island of Jan Mayen. The other is at the bottom of the ocean, spewing out mud and methane.

Text: Maja Sojtaric

Haakon Mosby mud volcano is a unique volcano at sea. It was discovered by accident in 1989 by researchers at the University of Bergen. They did surveys of the seabed of the continental margin in the Barents Sea, which is the part of the seabed situated between land and deep sea. And there they found the volcano, at 1300 meters depth.

"Usually one finds such volcanoes on the seabed of active continental margins, where an oceanic plate is forced under a continental plate. But this does not happen here. This is a passive continental margin. We rarely find volcanoes on passive continental margins. Haakon Mosby is a unique volcano as far as we know", says Professor Jürgen Mienert, director at CAGE .

Spewing out mud and methane

The volcano, which was named after a well known Norwegian oceanographer, has been probed with all sorts of sensors.

"All possible sensor technology has been used on this small volcano. Many of the major international marine geological institutions have done research there. I myself have been on the seabed with Russian underwater vehicle MIR 1 and MIR 2, to see the volcano. And still the volcano is in many ways a mystery for us", says Mienert .

The researchers do know is that volcano has been active at least 40 years. And it has blown out large amounts of hot mud and methane. It is particularly methane bubbles that interest Mienert . He´s curious as to what makes the volcano so active, and what happens to methane gas when it escapes.

Haakon Mosby Photo: Alfred Wegener Institut

Methane bubbles from Haakon Mosby mud volcano. Several tons of methane are released by the volcano each year. Photo: Alfred Wegener Institut

"Methane is a very potent greenhouse gas. It contributes greatly to the greenhouse effect. And there are large amounts of methane stored beneath the seabed. What will happen to global climate if this gas is released into the atmosphere?"

Volcanoes contribute to climate change

Volcanic eruptions have previously contributed greatly to dramatic climate changes, but there is a difference between volcanoes on the surface and under the sea.

"Reactions to methane in the atmosphere are different than the reactions in the water column. Around Haakon Mosby, we see that special bacteria eats up the gas. Methane can also be dissolved in water and passed around by currents, and never reach the atmosphere. But there are also several studies that suggest that the gas can actually reach the surface and thus the atmosphere. So what is it that causes methane to bubble up in the first place?"

Earthquakes?

Earthquakes and volcanoes are common companions, and it is often earthquakes that cause volcanoes to blow out. But earthquakes are rare in Norway.

"Passive continental margins do not experience earthquakes often. We have had seismic measurements of the Haakon Mosby over two years, to look at the frequency of earthquakes and whether they affect the volcano. And still we must say that it is unclear whether it is the seismic activity that controls blowouts from Haakon Mosby."

"There is no direct connection between the seabed and the deeper area beneath it, where the volcano gets the gas and the mud from. We believe that there possibly exists a system of chambers beneath the volcano that get filled and emptied. Gas and mud goes through several chambers before we get a blowout. In the individual chambers, which may be as deep as 1,000 meters below the seafloor, earthquakes may be acticvating this stuff. But also the tide and changes in pressure play an important role in the activity of Haakon Mosby mud volcano."

Sailing the seas

Professor Jürgen Mienert, director at CAGE.

Jürgen Mienert has a long career as a marine geologist. He has sailed most oceans, been on expeditions over 100 times with 50 different research vessels and worked for world leading institutions such as Columbia University in New York and the Woods Hole Oceanographic Institution.

He has also contributed to establishment of GEOMAR, the renowned German oceanographic centre in Kiel. So how did he end up in Tromsø researching, among other things, volcanic activity?

"In 1998 I held a talk at a congress in San Francisco when a nice lady ( prof . Karin Andreassen , editor. ) Asked me if I wanted to apply for a professorship in Tromsø. Investigating the Arctic ocean is exciting and challenging. And being so close to the research area was tempting."

Mienert has been the director of CAGE – a center of excellence in research on environment and climate at UiT – since 2012.

"We are a team of geologists, biologists, geophysicists and chemists looking into what 's happening with methane emissions in the Arctic Ocean. The volcano Haakon Mosby can give us very detailed local knowledge of an anomaly. It can not tell us anything about what happens to methane reservoirs in general."

"Gas hydrates, methane frozen into ice under the seabed, are little explored in the Arctic. Whether the methane gas is released from these hydrates depends on water temperature, ocean currents, water chemistry and microorganisms in the ocean. We investigate all this in the present, while we look at past data stored in sediments, in order to come up with general answer. It is a significant contribution to the understanding of global climate change that we face" emphasises Mienert.

Reference : Character of seismic motion at a location of a gas hydrate -bearing mud volcano on the SW Barents Sea margin .

https://cage.uit.no/news/scientists-intrigued-unique-volcano-ocean-floor/