What IS at the bottom of Belize's Great Blue Hole? Plastic bottles
What IS at the bottom of Belize's Great Blue Hole? Plastic bottles: Richard Branson's expedition to the giant sea hole found pollution next to startling signs of climate change
The complex cave system was submerged 10,000 years ago by melting ice
Branson sighted plastic bottles at the bottom of the hole at depths of 400 feet
He called the site 'proof of how oceans can rise quickly and catastrophically'
Belize's Blue Hole has never been fully explored due limits of technology
By Yuan Ren For Mailonline
Plastic pollution including water bottles has been found 400 feet (120m) below the ocean's surface during an expedition down a sinkhole known as the Blue Hole.
Virgin founder Richard Branson is behind the project off the coast of Belize, which set out to explore the complex cave system.
The Blue hole was once on dry land but became submerged around 10,000 years ago at the end of the last ice age.
It is hoped the information gathered during the expedition will shed more light on how climate change has impacted the planet over the course of millennia.
Plastic pollution has been found 400 feet below the ocean's surface during an expedition down an underwater sinkhole known as the Blue Hole. The Blue hole was once on dry land but became submerged around 10,000 years ago at the end of the last ice age
Virgin founder Richard Branson (left) is behind the project off the coast of Belize, which set out to explore the complex cave system. Branson was joined by Fabien Cousteau – an ocean conservationist, documentary maker, and grandson of famed explorer Jacques Cousteau (right)
The expedition at the popular tourist site deployed two three-man submersible submarines.
Branson and Fabien Cousteau – an ocean conservationist, documentary maker, and grandson of famed explorer Jacques Cousteau – spent hours deep inside the Blue Hole.
Two large floating vessels were also on hand to provide research and logistical support.
The team of divers and scientists performed a 3D scan of the site, including a sonar scan of the interior using military-grade technology.
In a blog about the expedition, Branson wrote: 'The real monsters facing the ocean are climate change – and plastic. Sadly, we saw plastic bottles at the bottom of the hole, which is a real scourge of the ocean. We've all got to get rid of single-use plastic.'
He warned of similar submergence events in the present day, calling what he saw at the bottom of the hole 'the starkest reminders of the danger of climate change I've ever seen'.
'It is proof of how oceans can rise quickly and catastrophically,' he added.
While divers have previously reached the bottom of the Blue Hole, the total darkness and difficult conditions limited their ability to collect scientific data.
The latest expedition is the first time that modern technology, in the form of a submarine, has given a scientific team time and access to study the geological formation in detail.
'There's a lot of discoveries left to be had there, including finding the sediment, looking at the variations in the walls, the oxygen and CO² content.'
'There's a whole laundry list of things that we are going to be doing there that haven't been done,' Cousteau said.
Submersibles allowed the team to spend more time at the bottom of the Blue Hole. The expedition is the first time that the Blue Hole has been properly explored by scientists.
Branson's Belize expedition was also in support of Ocean Unite, an organisation which brings leaders and voices together to promote ocean conservation. They are campaigning to protect at least 30 per cent of the ocean by 2030.
Cousteau's links to the Blue Hole go beyond just professional interest.
In 1971 his grandfather, famed French diver-explorer Jacques Cousteau, brought his research vessel Calypso 43 miles (70km) off the coast of Belize to explore the wondrous 1,000ft (300 m) long sinkhole.
Cousteau's team had discovered that the Blue Hole, the largest sea sinkhole in the world and one of Belize's main tourist attractions, was in fact a submerged cave that had formed over a period of tens of thousands of year.
JACQUES COUSTEAU AND THE GREAT BLUE HOLE
The Great Blue Hole was made famous by French ocean explorer Jacques Cousteau, who declared it one of the top five scuba diving sites in the world.
He brought his renowned research ship, the Calypso, to investigate the depths of the sinkhole in 1972.
The expedition found some submerged stalactites in the hole, and was able to conclude that the Blue Hole was formed before ocean levels rose.
The Great Blue Hole was made famous by French ocean explorer Jacques Cousteau (left), who declared it one of the top five scuba diving sites in the world. He brought his renowned research ship, the Calypso, to investigate the depths of the sinkhole in 1972.
Investigations by this expedition confirmed the hole's origin as typical karst limestone formations, formed before rises in sea level in at least four stages, leaving ledges at depths of 21 m (69 ft), 49 m (161 ft), and 91 m (299 ft).
Stalactites were retrieved from submerged caves, confirming their previous formation above sea level.
Some of these stalactites were also off-vertical by 5˚ in a consistent orientation, indicating that there had also been some past geological shift and tilting of the underlying plateau, followed by a long period in the current plane.
The tilt indicates that this was a movement of the land, rather than a rise in sea level alone.
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