The Surabaya Mud Volcano

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About Mud Volcanoes

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Fig.2_smaller mud volcanoe

Mud volcanoes are poorly understood geological phenomenon. These
volcanoes take place under subsurface layers with that has been built
up under pressure. They have been put under stress by the tectonic
activities of the crustal boundaries and over time have culminated various
gasses. A mixture of methane and carbon dioxide builds up and is waiting
to be released. The mound of mud is created by fluidized sediment
containing silt and clay. The mud can come from miles under the earth’s
crust, mixing with hydrocarbon gasses forcing the mud up to the surface.
Mud volcanoes can be as small as a few inches to hundreds of feet high
(see fig.1). Unlike the bubbling gas pots found in geothermal areas
(Yellowstone) the mud that erupts out of the mud volcanoes are cool to
slightly warm.

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Fig.1_mud volcanoe of Sidoarjo

As the mud is blasted or oozed out of the earth,
mounds of mud form the conical shape. Most of
these mud volcanoes are harmless and are fairly
small (only inches in height_see fig.2).These are
referred to as “craters”, which ooze forming small
flow
s.A mud volcano may be the result of a piercement structure created by a pressurized mud diapir which breaches the earth's surface or ocean bottom. Temperatures may be as low as the freezing point of ejected materials, particularly when venting is associated with the creation of hydrocarbon clathrate hydrate deposits.





Location

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Fig.3_left_Aerial view of Java Right_fault line

LUSI is located on the island of Java. (see_fig.3)The East Java basin is known for its “over pressured’ formations and the area has around 120 historical volcanoes. The most active areas in the world are along plate boundaries. East Java is part of the Indonesian Arc Islands, which located on an oceanic subduction plate off of the Sunda plate and the northeastward drifting Australian plate. Right off Java is the Sunda trench is the subducting Australian plate (2.4 inches per year). This constant friction often triggers frequent earthquakes, which then in result triggers lahars (mud volcanoes).





The Mud Volcano: "LUSI"

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On May 29, 2006, mud and gases erupted from a vent 150 meters away from a hydrocarbon exploration well close to Sidoarjo, East Java, Indonesia. LUSI (Lumpur Sidoardjo) volcanic mud eruption displaced around 30,000 people and has been flowing for 2 years. The reason for the eruption has been a controversial topic. There have been two main proposals for the cause of the mud volcano. The first cause of the eruption could be due to the 6.3 earthquake the struck Yogyakarta (250 km from Lusi) two days before eruption. Many state that the earthquake was too small to have caused any disturbance to the fault. In 2007 Durham University has published a scientific journal suggesting offshore drilling near the Banjar Panji may well be a more plausible cause of the mud eruption. Under examination it seems that the petroleum drilling has caused more stress on the already pressured fault line. PT Lapindo Brantas (an Indonesian oil and gas exploration company) could not control pore fluid intakes into the hole was the main cause of the disaster. First the oiling company has penetrated through about a dozen different layers of the sand, clay and shale (the fluidized sediment), which lay on top of a limestone layer (500-1300m. deep) The limestone layer was the last layer (barrier) keeping the various clay layers from being flooded, mixing with water and eventually turning the clay, silt and debris into mud. (see fig.4) At this point of the drilling, the borehole was still surrounded by a steel casing to help stabilize the drilling. Then a second drilling took place. The casing was left off this time and went 2,834m deeper. Since the drilling did not have the steel casing, steam and small amounts of gas erupted about 200m southwest of the well. And later, in early June (800-1000m) a couple more gas lines busted (hydrogen sulphide); and local villagers noticed hot mud at 212°F/100°C (previously the mud was cool, but the steam and broken gas lines have heated the mud).


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fig.4 layers of sediment

The 13 casualties were not due to the mud slide but to the oil and gas lines in the barriers which were ruptured. The aftermath of the eruption has severely damaged the economy and the mud continues to flow endlessly. There is enough mud to fill 50 Olympic sized pools daily (100,000 cubic m3) to 160,000 m3 (being the highest) and this is expected to last for at least a decade due to the steady rate of mud flow. The mud has filled villages and inhabitants realize they will not be going back to their homes. The main roads have been covered in mud and thousands have lost their jobs. Most of the jobs in Indonesia come from American factories (i.e. Nike). Attempts to stop the incoming mud from further causing damage involves filling nylon bags with mud or dirt to create barricades, channeling the mud into the Kali Porong River leading to the ocean 20km east (ineffectively because of the low gradient) and people have also been trying to build dams with drier mud with bulldozers. A concrete dam, to block the mud flow has been suggested in June 2007, but has yet to be seen through. Another attempt to stop the mud was when the company “Boots and Coots” came in to try and plug to the well, but when they were about to plug it; the plan was called off. This was very controversial because not only was it very expensive ($10 million) to get there and not attempt to plug the well, but if it had succeeded then it will be a proven fact that the oil well is the cause of the disaster.

In May 29, 2008 (the second year of LUSI) scientists have found out that the center of the volcano has collapsed 3m overnight. These sudden changes imply the beginnings of a caldera volcano. The research team from Durham University UK, and the Institute of Technology Bandung, in Indonesia suggests that the depletion of mud and water from the ground has now left the earth hollow and is no longer supporting the crust. The study also shows while some parts of Sidoarjo are sinking, others are rising. This implies that the Watukosek fault system has been reactivated because of the eruption.


Sources

http://earthquake.usgs.gov/eqcenter/eqinthenews/2006/usneb6/

http://pubs.usgs.gov/of/2008/1019/pdf/OF08-1019_508.pdf

http://www.geolsoc.org.uk/gsl/geoscientist/features/page4009.html

http://folk.uio.no/adrianom/et%20al%20Mazzini%20et%20al/Mazzini_EPSL_07.pdf

http://online.wr.usgs.gov/calendar/2008/jan08.html