Mysterious mounds of southern Hood Canal:dumpsites,landslide deposits or glacial debris

Abstract

In 2005 two large seafloor mounds 30-40m high and approximately 350m in diameter were partially imaged in Southern Hood Canal.The geophysical and sediment data indicate that the mounds are at least 12,000 years old and consist of much coarser material than the surrounding seafloor. The shape and size of the mounds, including the subbottom portion, are consistent with an interpretation that they are glacial features- drumlins- created during the Vashon Stage glaciation of the Puget Lowland.