The mud volcano in Indonesia continues to pour out hot material so the government is seeking to stop it with cement balls which have been used in Azerbaijan. Mud volcanoes are associated with gas and oil fields and tectonic plate movments.
Engineers and geologists have begun work to plug a mud volcano in Indonesia using large concrete balls, but were forced to put the project on hold when a steel cable used to hoist the balls melted and broke.
The plan involves lowering nearly 1,500 concrete balls, each weighing around 250kg, into the geyser at Sidoarjo, near Surabaya in East Java.
The volcano began erupting in May. Over the past few months a creeping sea of sediment has covered factories, thousand of homes, displaced at least 13,000 people and blocked major roads into Indonesia's second-largest city.
When I saw the photos of the cement balls, I was curious if it had been used in the past and how it fared. But first, it would help to know more about mud volcanoes. In the USA, we have places that have these sorts of geological events such as the famous Yellowstone Park, for example.
The motivating force responsible for a mud volcano is, in part, simply the weight of rock overburden borne by the fluid content of undecompacted shales. However, mud volcanoes all over the world are associated so invariably with quietly or explosively escaping methane gas that it is reasonable to conclude that the presence of methane gas in the subsurface is also an essential feature of the phenomenon. The mud of the volcanoes is a mixture of clay and salt water which is kept in the state of a slurry by the boiling or churning activity of escaping methane gas. Probably the methane gas was derived either directly from organic matter in muds or shales or from secondary accumulations in sand stringers within the source-rock shale or from larger reservoirs just above or just below such shales. Some liquid oil often, but not always, is associated with the hydrocarbon gases of mud volcanoes.
Every twenty years or so, a mud volcano may explode with great force, shooting flames hundreds of metres into the sky, and depositing tonnes of mud on the surrounding area.
This was the kind of eruption that witnesses described seeing on a hillside 15 kilometres (nine miles) outside the Azerbaijani capital Baku on Thursday morning.
"There was a big explosion, and a huge flame started coming from the hillside," said one witness. "It looked as though an animal was trying to get out of the ground.
"The flame was unbelievably big, about three hundred metres high. It was surrounded by dense, black smoke, and lots of mud was being thrown into the air.
Geologists know that the best place to find oil or gas is to look for places where salt and limestone overlay organic matter. As the tectonic plates shift, they also tip sections of continents and this also causes the fluids trapped under salt or limestone to flow into chambers in the strata, often pooling in places where it is easy to tap like the Gwaihir oil fields in Saudi Arabia.
This chart clearly shows it takes an earthquake greater than a 4.5 to trigger an allied mud volcanic eruption. The government of Indonesia originally accused the drillers working at that well of causing this eruption but the geologists have made it clear, the earthquake that occured just before this eruption was probably the cause. The government of Indonesia is more interested in getting someone to pay for the destruction of so many homes and businesses.
There is another issue at work here: as humans pump out all the gas and oil, this changes the geology of a region. Pumping in water into the potential site of a mud volcano is obviously foolish. But the pumping goes on, this includes pumping groundwater worldwide which is causing large sections of landscape to collapse or subside. Just for example, no one has the slightest idea how deadly it might be, pumping out all the water from the giant Ogallala water reservoir. This area is virtually the entire Midwest halfway between the Mississippi River and the Rocky Mountains.
The Caspian Sea is a geologically as well as politically very interesting area. I drew the map at the top of the story, showing an exaggerated view of the different elements of the lay of the land based on a satellite photograph of the whole region. Africa, Europe and Asia all converge here. Geologists believe that the Black Sea, the Caspian Sea and the Aral Sea are all the last remnants of the once huge Tethys Sea (Ocean). The Tethys ebbed and grew for millions of years. Because of this changing condition, there are many layers of different materials which is ideal for creating fossil fuels.
Unlike the deep oceans, the Tethys was fairly shallow because it was pinched to varying degrees by the surrounding countinents that made up Pangea 250 million years ago. When Pangea broke apart, the Tethys Sea deepened while what is now Europe and the Caspian region today, was underwater. So 100 million years ago, sea life flourished there which is why there is so much dead biomass produced during that time which, thanks to geological forces, has turned into coal and oil from England to the knees of the Himalayan mountains.
Some 50-60 million years ago, before the beginning of the Tertiary Period, a vast oceanic basin extended from west to east across Southern Europe and Central Asia, linking the Atlantic Ocean and the Pacific Ocean. It was the salty Tethys Sea. By the middle of the Tertiary Period, as a result of crust upheavals, the Tethys Sea had become separated first from the Pacific Ocean and later from the Atlantic.
Major crust movements led to mountain-building in the Miocene (from 5 to 7 million years ago) and the formation of the Alps, the Carpathians, the Balkan Mountains and the Caucasus Mountains. As a result the Tethys Sea shrunk in size and became divided into a number of brackish basins. One of them, the Sarmatic Sea, stretched from the present location of Vienna to the foothills of the Tien Shan Mountains and included the modern Black Sea, the Azov Sea, the Caspian Sea and the Aral Sea. The Sarmatic Sea was separated from the ocean, and gradually its salinity fell as a result of the inflow from rivers. It is assumed that the salinity in the sea was even lower than in the modern Caspian Sea. Much of the marine fauna endemic to the Tethys Sea became extinct. However, it is interesting to note that typically oceanic animals, such as whales, manatees and seals, continued to inhabit the Sarmatic Sea for a long time, before they too disappeared.
The Caspian Sea's bed is below sea level and this is true of the land on some of its shores because this is still a low spot on the earth, unlike Death Valley, of course, it is filled with water. The drawing I made from the satellite photos shows clearly how Arabia, as it is shoved harder and harder into the last of the Tethys' basin, has raised a ridge of mountains on one side of this basin and the European side is also high mountains, the Caucasus range. It is interesting that the point where these continents collide still has a deep depression instead of it just building up as mountains directly.
The map here shows various fault lines in the Caspian and the arrows show the direction of movement of the continents. These movements are particularily complex right at the southern end of the Caspian Sea and the mud volcanoes are most active in these conflicting areas. As the former seabed is squeezed and folded, gases are released. And fissures allow water to seep in and this mixes with the soft rocks below and turns them into hot mud.
Michael E. Wysession, assistant professor of earth and planetary sciences, Washington University, has discovered and mapped through seismic wave analysis a continental-sized mass of rock that directly corresponds to the location of the ancient Tethys Sea, which disappeared slightly less than 200,000,000 years ago. The two-dimensional image is the highest resolution map yet derived of this part of the inner Earth.
Through plate tectonics--the sliding movement of the Earth's dozen or so plates--the ocean floor supporting the Tethys Sea dipped into the Earth in a process called subduction, where one plate descends beneath another. Over tens of millions of years, the Tethys Sea closed up, the action causing present-day India to collide into Asia, which formed the Himalayan Mountains and the entire Tibetan Plateau. The only surface remnant of the Tethys Sea today is the Mediterranean Sea.
Wysession believes he has found the rest, but it's 2,000 miles beneath the surface. He analyzed 750 digital seismic waves from sophisticated seismographs that have recorded scores of large earthquakes over the past 15 years. From this data, he has rendered the world's most detailed two-dimensional map of this massive subterranean world. The seismic waves from the earthquakes are large enough to cause significant energy to bounce off the Earth's core and back to the surface.
He found a continental-sized region making up one very hot area, where the wave velocities move very slowly, surrounded by three cold areas, where the seismic waves travel at a comparatively fast pace. The hot area comprises older material sunk deeper into the Earth. This material has had a chance to heat up, unlike in the cold areas where it hasn't had an opportunity to settle in.
I looked at satellite photos of various geologically active regions where subduction is occuring and one sees these areas as I drew in this maps here, where the land has collapsed but is surrounded by mountains. Helmland in Afghanistan is one such area. The Black Sea/Caspian Sea complex is not the same thing, this is a trapped ocean like the Mediterranean, growing smaller and smaller. The seabed of the Tethys Ocean is now at the top of the world as the Himalayan mountains have grown. This is also true of the Alps. The Alps are less than 10 million years old.
It is interesting that as Italy is pressed into Europe, raising the Alps which was also part of the Tethys seabed, Lombardy is at sea level and just on the north side of the Alps, Lake Geneva is, along with other lakes, in a low-lying fold in the continent which rises to the north again, this being the wellspring of the Rhein river, for example. The Inn river runs along this fold through Austria and to the Black Sea along with the Danube which has a wellspring next to the Black Forest mountain range.
I used to pick flowers in the meads where the Danube springs. It is a very beautiful place, great for bird watching.
The seabed of the Tethys which is being alternately pushed sky high is also collapsing into folds such as the seas between Italy and the Adriatic coast. It seems to me that the mountain-building actions of plate tectonics is causing parts of the continents to collapse at the same time and perhaps this is because it is really seabed and not continental material.
The spectacular Tibetan plateau is merely one of the biggest, most outstanding examples of a common geological event. All along the Mediterranean's northern shores, mountain building is happening at an astonishing speed. We still understand little as to how these things happen, exactly. In Russia, Lake Baikal is the deepest on earth and holds more water than any other lakes except for the greatest of the Great Lakes and yet it is a very narrow, long body of water that has little surface area. The Caspian Sea isn't very deep and the Aral Sea is barely a pond at this point as it is rapidly drying up due to human interventions.
But it is doomed in the end for the entire land there is constantly rising. Will the Mediterranean end up like Lake Baikal? Will the old Tethys seabed fall away and create a thinner crust which could then collapse into a very deep fold? And thus, keep the water intact but only as a long, narrow chain of rift lakes?
Forecasting distant geological events is like looking into a fuzzy crystal ball. We can only guess. Thanks to modern geological advances, it is easier each year.