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The volcano, Kick 'em Jenny, sits off the northern coast of Grenada

Officials have raised its threat level to orange, which means an eruption is expected with little notice

CNN  — 

An active underwater volcano is rumbling beneath the Caribbean Sea. And scientists say an eruption could sink ships and shoot up hot rocks into the air.

The volcano, Kick ‘em Jenny, sits off the northern coast of Grenada. Officials raised its threat level Thursday to orange, which means it could erupt with less than 24-hour notice.

Kick 'em Jenny

Kick ‘em Jenny started stirring on July 11, and has produced more than 200 small earthquakes since then, according to the Seismic Research Centre at the University of the West Indies.

Even though the crater is about 600 feet (180 meters) below the surface of the ocean, the volcano is a hazard to locals and ships in the region.

Stay away, ships warned

To clear its path and reduce risks, scientists set up an exclusion zone for ships around the volcano. Recreational ships must stay at least 5 kilometers (3 miles) away from the summit of the volcano.

If it erupts, Kick ‘em Jenny could displace seawater and produce a tsunami, though the risks of that are relatively low, scientists say. If an eruption causes a tsunami, it is likely to be small and confined to nearby islands.

But other risks to shipping and marine vessels in the region are especially significant.

Underwater or submarine volcanoes release intense amounts of gas into the sea during eruptions – and at times in between eruptions during a process called degassing.

Such gas bubbles lower water density and can cause ships to lose buoyancy and sink.

Hot rock projectiles

In addition to putting ships at risk of sudden sinking, an eruption could throw hot rocks, known as ballistic projectiles, up through the water and into the air far above the ocean surface. Such rocks can go up to 3 miles (5 kilometers) from the volcano and have the ability to significantly damage or destroy ships.

One of Grenada’s worst maritime disasters is believed to have occurred as a result of degassing from the Kick ‘em Jenny volcano in 1944. At least 60 people died when a ship sank with 60 people on board.

Kick ‘em Jenny has erupted a dozen times since it was discovered in 1939, scientists say.

Its last eruption was in 2001.