A Belize whale-shaped island with a “giant blue vent” — Earth seen from space

This incredible photo of the astronaut shows the strange whale-like shape of a tropical island in Belize. The reef-covered structure features the Great Blue Hole, one of the deepest ocean sinkholes on Earth, which looks like a whale’s “furpet hole” when viewed from space.

The whale-shaped land known as Lighthouse Reef is located about 80 km (50 miles) off the Caribbean east coast, and its “head” to “tail” is approximately 26 miles (42 km) long. There are no settlers here, but it is visited annually by over 10,000 tourists, including many scuba divers.

Because this island is an atoll, the majority of the island is underwater, covered with shallow coral reefs, and only a few sandy areas known as cays protruding above the surface. The turquoise waters of the atoll are only 6 to 20 feet deep (2 to 6 meters), but near the center of the island there is a dark circle that stretches far deeper.

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The Great Blue Hole is an underwater sinkhole with a nearly circular opening spanning 1,043 feet (318 m). The hole has a maximum depth of 407 feet (124 m), and is one of the deepest sinkholes on the planet, and it was only recently properly investigated.

Related: See all the best images of Earth seen from space

Lighthouse Reef is part of the wider Belize Barrier Reef, listed as a UNESCO World Heritage Site, and is home to a variety of marine life, including a variety of fish, such as vera, snapper, and goby, as well as large animals such as crocodiles and sea turtles.

One of the island’s most famous water spots, Half Moon Key (located at the tip of the hump on the whale’s back), is home to a variety of birds nesting in coconut palm trees, as well as endangered species of geckos and anols.

Great Blue Hole

The Great Blue Hole is believed to have initially been formed as an overwater cave system, as evidenced by stalagmites and stalactites discovered in underwater caves diverging from the main sinkhole. However, the end of the last ice age caused sea levels to rise, causing flooding around 10,000 years ago.

The hole became famous in the 1970s when famous marine explorer Jacques Cousteau visited the island and began creating maps of its depths from his famous ship Calypso. Cousteau later described the sinkhole as one of the world’s “top five scuba diving sites.”

In 2018, explorer grandson Fabian Cousteau and British billionaire Richard Branson led a submarine expedition to explore the Great Blue Hole, creating the first 3D map of the structure. One notable finding on this expedition is the discovery of a layer of hydrogen sulfide about 107 feet (33 m) thick towards the bottom of the hole. This layer is fatal to most marine animals that invade it because there is no oxygen-free layer, or dissolved oxygen.

The expedition team also found the bodies of two scuba divers who were missing while exploring the Great Blue Hole. Their bodies were completely preserved by a hydrogen sulfide layer, according to Newsweek magazine. The expedition, in honor, decided to leave the body there. It is known that at least one other diver has gone missing in the sinkhole.

More recently, scientists analyzed the area’s historic tropical cyclone using sediment cores taken from the bottom of sinkholes earlier this year, finding that these storms have become more frequent in the past 6,000 years.