A serious natural disaster mud volcanoes spew toxic mud and kill life in the areas affected. Close cousins to magmatic volcanoes, mud volcanoes too erupt powerfully with millions of cubic meters of hydrocarbon gases and tons of mud and hurl flames as high as several hundred meters.
 What is a mud volcano?
Mud and gas accumulate when sea sediments are trapped in volcano vulnerable zones, where one tectonic plate slides under another. They can erupt out of volcanic cones or simply from a crack in the ground. Pressurized gas and mineral water beneath the earth's surface find release through mud volcanos. It is said that mud volcanoes have roots that go several kilometers underground and act as safety valves for high underground pressure.
Mud volcanoes have erupted on every continent, but are abundant in the South Caspian region (offshore and onshore Azerbaijan) and offshore Indonesia in the East Java Basin. The volcano in Indonesia named Lusi, which has been erupting continuously since 2006, has already devastated homes and businesses in Sidoarjo, East Java, displaced around 10,000 people and killed 14.
The world largest and highest mud volcano is located in Balochistan, Pakistan. Rising up to 300 feet, these volcanoes not only appear on land but also on small islands off the Arabian Sea
 What causes mud volcano
When oceanic tectonic plate slides underneath a continental plate, sediments accumulate rapidly and water is trapped in its pores. The trapped water stops the sediment from being cemented by pressure as it otherwise would have done. This results in a reservoir of mud being trapped underground. In the case of the East Java mud flow, the mud is thought to have come from a reservoir some 2.7 kilometres below the Earth's surface.
A number of things can create a crack that allows trapped mud to bubble to the surface; particularly earthquakes and drilling.
Mud volcanoes are generally found where stratified rocks with cores of mobile sediment, deposited rapidly and trapping water, fold down from a crest. Pressure exerted on rock formations by deep gas deposits, or gas generated closer to the surface, can be an element in the formation of mud volcanoes.
Mud volcanoes occur when gas pushes mud from deep within the earth upwards towards the surface with such great force that it can lift and break rock formations. As a result pieces of rock are sometimes thrown out with the mud when the volcano erupts.
 Nature of mud volcanoes
Mud volcanoes do sometimes erupt powerfully, but in most parts of the world gases bubble passively from the tiny "craters" at their summit, and ooze out small flows of mud. Mud from mud volcanoes are also cold, or perhaps only slightly warmer than the ambient ground temperature.
Large explosions are said to occur due to excessive accumulation and combustion of hydrocarbon gases, such as methane. Once these gases are released, the mud volcano returns to a passive state, and may not explode even for centuries
Gases expelled from mud volcanoes are primarily methane and carbon dioxide, making them one of the important sources of greenhouse gases. There are estimated to be 1,100 mud volcanoes on land and 100,000 more underwater, together emitting 185 million pounds of greenhouse gases each day. Though insignificant compared to industrial sources worldwide, this is still a significant amount of gas.
 Mud volcano frequencies
Mud volcanoes have both active and extinct phases. Dormancy between eruptions can extend from three years to 80-90 years. There are differences in the size and the impact of the eruptions. But there are few disasterous consequences of such eruptions as they occur far from pupulated centers.
- Mud volcano floods Java -- Bio-Ed Online
- Mud Volcanoes
- Here's the dirty truth about mud volcanoes