Fiery explosion produced by muddy phenomenon

A towering wall of fire brightened the night sky over the Caspian Sea on Sunday due in part to a unique geologic formation.

Just after sunset on July 4, a large explosion and fireball could be seen offshore of Baku, the capital of Azerbaijan. The cause of this explosion was a phenomenon many may not have ever heard of outside of the countries situated along the Caspian Sea.

The Sunday blast occurred on a tiny island offshore of Azerbaijan known as Dashli Island.

An impressive fireball could be seen after the eruption of what is called a mud volcano.

"There are about 1,100 mud volcanoes that have been identified around the world, and nearly 400 of them can be found in and around Azerbaijan," AccuWeather Senior Meteorologist Tyler Roys said.

"Eruptions of mud volcanoes are driven by a deep mud reservoir that is connected to the surface," Roys explained.

When these mud volcanoes erupt, more than just mud, boulders and rocks can be lofted above the surface. Mud volcanoes can also tap into and launch oil or natural gases into the air.

"The majority, about 86 percent, of the gas released from an explosion is methane," Roys said.

In the right concentration, methane gas is highly flammable and can react explosively. Hence, the tell-tale fireball that marks many mud volcano eruptions.

The ignition of mud volcano fireballs likely occurs naturally and can be the result of two main processes.

The first explanation involves sparks. When rocks and debris smash into each other as they are launched upwards during the mud volcano explosion, the friction between them can cause a spark that lights the flammable gas in place.

The second explanation involves pressure. Some researchers suggest that rapid pressure change during the explosion alone may be enough to ignite the gas.

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"Unlike other volcanoes, the temperature of a single mud volcano remains fairly steady. However, from mud volcano to another, temperatures can range from as high as 212 F (100 C) to as low as 35 F (~2 C)," Roys explained.

According to Roys, some of the mud volcanoes with lower temperatures have been known to be used as spa-like mud baths.

Sunday was not the first time the Dashli Island mud volcano has erupted.

According to Dr. Mark Tingay, an adjunct associate professor in geomechanics and drilling engineering at the University of Adelaide in Australia, the Dashli Island mud volcano also had "major eruptions" in 1920 and 1945.

Thankfully, while the fireball from the most recent explosion looked impressive, no injuries or damage to nearby oil-drilling platforms were reported.

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