Mud volcano explodes in the Caspian Sea

July 4 was Independence Day in the United States—a day which typically features huge fireworks displays. But the biggest fireworks going off that day were actually halfway across the world in Azerbaijan.

This country sits between Russia and Iran on the shores of the Caspian Sea. And on that Sunday, a massive explosion skyrocketed above the sea, on a tiny island about 75 km (45 miles) from the coastal capital of Baku.

WATCH: Large explosion reported near oil platform in the Caspian Sea; officials say it may have been caused by a mud volcano pic.twitter.com/eqwNw110bF

— BNO News (@BNONews) July 4, 2021

The cause?

Experts believe that it was set off by an underwater mud volcano.

And what exactly is that?

There are a few questions here, but let's start with the most obvious: What is a mud volcano?

First off, it is not a true volcano—an opening in the Earth's crust that spews forth lava, or molten rock. Instead, is it a super heated slurry (mixture) of water and mud, as well as gases, especially methane. The heat and pressure pushing up underneath this mixture can create dome-like structures. And sometimes, this pressure becomes so great, that you get an eruption of stuff. Normally, that stuff is large amounts of methane gas, though it can also include mud, rock, and water.

How would it explode?

Methane is a highly flammable gas. That means it burns easily. Not surprisingly, it is actually used as fuel around the world. Sometimes during a mud volcano eruption, sparks caused by colliding rocks ignites the gas. And Ka-BOOM! You get a huge explosion.

A really huge explosion in this case, as this aerial video shows.

Why in Azerbaijan?

Azerbaijan is a fairly small country—only a little bigger than the province of New Brunswick. But of the 1,000 or so known mud volcanoes in the world, it has around 400 of them. It is also an area rich in oil and natural gas. All of these 'explosive' features have given the country the nickname 'The Land of Fire'.

In fact, when the explosion first happened, many people suspected that an Azerbaijani oil rig on the Caspian Sea had exploded. Thankfully, that was not the case. But it is clear that all of these reserves of oil and gas—not to mention the mud volcanoes—can really keep you on your toes!