An underwater canyon deeper than the Grand Canyon, carved by currents when sea levels were lower. The walls preserve sea level records going back to the last ice age.
United States Geological Survey, Public domain, via Wikimedia Commons
A scar on the continental shelf
Just beyond the world-famous Ningaloo Reef lies a massive underwater feature: the Exmouth Submarine Canyon, part of the larger Cape Range canyon system. This immense submarine valley cuts deep into Australia's continental slope. While precise dimensions are hard to state for such a complex system, research expeditions have mapped its features, revealing a steep southern wall with slopes of 30-50 degrees. This wall shows evidence of powerful erosion.
The canyon was not carved by a river in the traditional sense. Its primary architects are turbidity currents—powerful, fast-moving underwater avalanches of sediment, sand, and water. These currents were most active during past ice ages when global sea levels were much lower. During the last glacial maximum, around 20,000 years ago, sea level was approximately 125 meters lower, exposing vast sections of the continental shelf. Ancient rivers flowing across this exposed land would have dumped sediment directly at the canyon head, triggering the erosive turbidity currents that carved the deep gorge over millennia.
A library of climate history
The walls of the Exmouth Submarine Canyon are a geological record. The northern side of the canyon features a series of small steps or terraces. These formations are ancient shorelines, etched into the canyon's slope as sea levels fluctuated between glacial and interglacial periods. Scientists can study these terraces to reconstruct a detailed history of sea level changes in the region.
The canyon connects the shallow continental shelf and the deep abyssal plain. Research voyages, such as those by the Schmidt Ocean Institute's vessel R/V Falkor, have used multibeam sonar to create high-resolution maps of the seafloor here. Remotely Operated Vehicles (ROVs) like SuBastian descend thousands of meters to collect geological samples and imagery. These expeditions have confirmed that the canyon system is still being shaped by sediment flows today. The rock types vary throughout the canyon, from limestone to volcanic rock, providing habitats for deep-sea organisms.
The shape of the canyon funnels nutrient-rich cold water from the depths up toward the surface. This upwelling supports a burst of life, forming the base of a food web that sustains the incredible biodiversity of the adjacent Ningaloo Coast World Heritage Area. This process supports the entire ecosystem, including the whale sharks that aggregate in the area between March and July. The region is a critical nursery and feeding ground for humpback whales and supports many sharks, rays, and sea turtles. In the canyon's deep, dark waters, scientists have discovered arrays of deep-sea life, including glass sponges, gorgonian corals, and crinoids (sea lilies), many of which are new to science.
💡Fun Facts
The canyon system is a known feeding ground for pygmy blue whales.
Turbidity currents, the underwater avalanches that carve canyons, can reach speeds of up to 70 kilometers per hour.
During a 2020 expedition, researchers discovered as many as 30 new species within the Cape Range and Cloates Canyons.
The canyon is part of the Gascoyne Marine Park, a protected area recognized for its ecological importance.
