The Yelland Stone Rows is a prehistoric monument of two parallel rows of small standing stones located on the tidal mudflats of the River Taw estuary, in Devon, England. Since the 1990s, the ancient stone alignment has disappeared from view into the silt and tidal debris. The site is within the nature reserve of Isley Marsh, and is owned by the Royal Society for the Protection of Birds (RSPB). Description The Yelland Stone Rows is a prehistoric stone alignment of two parallel rows of small standing stones. The site is situated on the tidal mudflats of the estuary of the River Taw, and is currently within the nature reserve of Isley Marsh. The stone alignment consists of at least 18 sandstone pieces, at least 30 cm high and 22 cm wide, positioned in a pair of parallel rows, up to 2.5 m apart. Since the late 1990s, all the stones have been covered by silt. Due to its large population of migratory and overwintering birds, the preserve is owned by the Royal Society for the Protection of Birds (RSPB). Rare plants can also be found on the site, including rock sea-lavender. History Stone alignments date from the Late Neolithic period (4500 BC - 3500 BC) to the Middle Bronze Age (1500 BC - 1000 BC). The Yelland Stone Rows were excavated by archaeologist, E. H. Rogers in the 1930s. A partial excavation uncovered eighteen stones arranged into nine standing pairs. Near the stones, Rogers discovered flint tools and evidence indicating human occupation of the site during the Mesolithic, Neolithic and Early Bronze Age eras. In 1932, the tallest standing stone measured 40cm in height above the silt, and the rows were determined to be 56m in length. By 1983, only seven stones were visible above the mud and the remaining stones disappeared from view over the next several years. By the 1990s, the stones were no longer visible. According to Charlotte Russell, an English Heritage project officer, "The [Yelland] power-station closure resulting in less discharge into the sea and less lively current, allowing sediments to settle, is one suggested cause [of the disappearing stones]." ... other factors, like silting up of the estuary in the absence of shipping, changes to railway and flood-bank construction in the area, and changes in runoff from upstream may all have played a role." In 2018, Historic England announced funding for a new archaeological investigation