In 2006, Australian caver Kim Van Dyke noticed something unusual while walking through a reserve near Buchan in Victoria’s East Gippsland. A small patch of grass was moving, even though the surrounding vegetation was completely still and there was no wind.For most people, the movement might have seemed insignificant. For Van Dyke and her husband, John, it suggested something hidden beneath the ground. They began digging and soon discovered rock, and evidence of an underground current of air.That small clue led to the discovery of Elk River Cave, a vast subterranean system concealed beneath a seemingly ordinary paddock. Nearly two decades later, explorers have mapped 3.13 kilometres of the cave, making it one of Victoria’s longest. At a depth of about 135 metres, it is also among the state’s deepest known caves, as per a report by ABC News.A hidden world beneath the paddockElk River lies near the small town of Buchan, in Victoria’s East Gippsland, on Gunaikurnai Country. The region is known for its limestone formations and extensive cave systems, many of which have been shaped by water over immense periods of time.Beneath the green hills, underground waterways have been carving through limestone for more than 350 million years. From the surface, however, there was little to suggest that a major cave system existed below the grassland.The location where Van Dyke noticed the moving grass was a doline: a sunken area formed when limestone dissolves underground and the surface gradually collapses or settles. These depressions are common in karst landscapes, where water moves through cracks and cavities in soluble rock.The unexpected movement of the grass indicated that air was travelling through a hidden opening. After digging beneath the patch, the cavers found the entrance to a passage that would eventually become known as Elk River.For the local exploration team, the discovery was the kind of moment cavers dream about. A small surface feature had provided a clue to an unseen landscape below.The first descentVan Dyke returned to the site with caving equipment and fellow explorers Eric Munro and Laurie Brown. She became the first person to enter the newly uncovered passage.The early exploration revealed a flowing underground streamway. The discovery was particularly important because researchers and cavers had long suspected that a significant underground river existed in the area. Elk River helped solve some of those century-old questions about the region’s geology and hydrology.The passage was not easy to explore. Cavers had to negotiate narrow sections, mud, darkness and cold water. Some routes ended at pools known as sumps, where the cave passage continues underwater. Beyond these points, ordinary caving equipment was no longer enough. Divers would be needed to investigate whether the system continued.The cave’s hidden river became the focus of an extended exploration effort involving members of the Victorian Limestone Caving Team and specialist cave divers.Exploration continued underwaterFinding the entrance was only the beginning. Mapping the cave required repeated expeditions, technical skill and a willingness to enter environments where even small mistakes could have serious consequences.Cave divers explored submerged sections of the streamway, pushing beyond areas that had stopped earlier teams. Among those involved in the exploration were experienced divers Agnes Milowka and Jim Arundale. Their efforts helped extend the known cave system and revealed additional sections of underground passage.Earlier accounts of the system recorded more than a kilometre of stream passage, while later exploration expanded knowledge of the cave’s length and depth. The cavehas also been referred to as the Murrindal Potholes Eastern Master Cave, reflecting its connection to the wider network of potholes and underground waterways in the area.Exploration of this type is slow and methodical. Teams must survey each passage, record its direction and elevation, document geological features and establish safe routes in and out. Underwater sections require additional planning because divers must manage air supplies, lines, visibility, water temperature and the possibility of complex passageways.The result is not simply an adventure story. Every metre mapped adds to scientific knowledge of how water has shaped the region over geological time.Why the discovery mattersElk River is important because it connected a visible surface landscape with a much larger hidden system below it. The underground river helped explain where water travelled through the limestone and how the area’s caves were related to one another, as per ABC News.Caves can preserve clues about geological history that are difficult to see at the surface. Flowing water creates channels, chambers and deposits, while changes in water levels can leave marks on the cave walls. Sediment, rock formations and the direction of underground passages can help researchers reconstruct the evolution of the landscape.The cave also demonstrates how much remains undiscovered, even in places that appear familiar. The entrance was hidden beneath grass in a landscape that people had walked through before. Yet a major cave system had remained concealed underground.That sense of mystery is one reason Buchan has become a significant location for Australian cave exploration. The area is already known for its limestone caves, but Elk River showed that the region still held major discoveries.A dangerous and demanding pursuitCave exploration is not the same as visiting a tourist cave. There are no paved paths, handrails or artificial lighting inside Elk River. Explorers may need to crawl through tight passages, wade through water and carry equipment through mud and uneven terrain.Flooding is another serious concern. An underground stream can rise quickly after heavy rain, changing a passage that was previously accessible into a dangerous flow. This is why experienced cavers carefully assess weather, water levels and equipment before entering.The cave’s depth and submerged sections make it particularly challenging. At approximately 135 metres, it is not only long but vertically complex. The exploration team has had to combine traditional caving techniques with specialist diving skills to continue mapping the system.For those involved, the difficulty is part of what makes the discovery meaningful. Every new chamber or passage represents a place that may never have been seen by a human before.A discovery that continues to inspireTwo decades after the first entrance was found, Elk River remains a work in progress. More than three kilometres have been explored, but cave systems often contain passages that are difficult to access or separated by underwater sections.The original discovery also continues to capture public imagination because of how ordinary it seemed at first. There was no dramatic collapse or obvious opening in the ground. Instead, one caver noticed grass moving in a quiet reserve.That detail captures the spirit of exploration: major discoveries do not always begin with advanced technology or a carefully planned expedition. Sometimes they start with someone paying attention to an unusual sign in the landscape.Today, Elk River stands as a reminder that some of Victoria’s most remarkable environments are hidden below the surface. The cave was shaped by water over hundreds of millions of years, but its modern story began with a patch of grass, a curious observation and a decision to dig.What lay beneath was not merely a small cavity in the limestone. It was a deep, flowing and interconnected world; one that has since become one of Victoria’s most significant cave discoveries.
