Australian scientists have discovered a detached reef more than 500 metres high – taller than the Empire State Building – at the northern end of the Great Barrier Reef. The “blade-like” vertical reef about 130km off Cape York, Australia’s north-eastern tip, was found during a 3D seabed mapping exercise conducted from a ship owned by the Californian non-profit Schmidt Ocean Institute. Tom Bridge, from the ARC Centre of Excellence for Coral Reef Studies at James Cook University and the expedition’s principal investigator, said the reef was 1.5km wide at its base and rose half a kilometre to within 40 metres of the surface. It is the first large detached reef found in the area since the late 19th century when seven others were discovered over a 150km stretch of ocean, Bridge said. “It’s a big reef not to have known about,” he said. “What it highlights is how little we know about a lot of the ocean, even the Great Barrier Reef. The marine park is 344,000 square kilometres – bigger than many European countries – and only about 6 or 7% of that is typical shallow-water reefs. “We know more about the surface of the moon than we know about what lies in the depths beyond our coastlines.” Detached reefs are bedded to the ocean floor off the continental shelf but are not part of the main body of the Great Barrier Reef. The newly discovered reef does not appear to have a lot of hard corals in its upper section, but has “an incredible abundance” of sponges, sea fans and soft corals, suggesting the area is rich in nutrients carried by strong currents and upwellings of deep waters. Bridge said the camera on the underwater robot used to explore the reef showed it was home to plenty of reef fish, including tiny hatchetfish and silvertip, and grey reef sharks. Video of the discovery from the robot, known as SuBastian, was live-streamed and posted on YouTube. “To not only map the reef in 3D detail but to also see this discovery with SuBastian is incredible,” the expedition leader, Rob Beaman, said. The discovery is likely to lead to years of study. The Schmidt Ocean Institute ship, the Falkor, is on a year-long exploration of oceans surrounding Australia. Scientists aboard the ship plan to continue mapping the northern Great Barrier Reef until mid-next month. The institute said earlier discoveries on the trip included what is believed to be the longest recorded sea creature, a 45-metre siphonophore, in a canyon off the Ningaloo coast in northern Western Australia. It said it had found potentially dozens of yet-to-be-described species, including black coral, sponges and scorpionfish.