When the oil reaches the shoreline, on rocky shores some components of the oil evaporate, leaving behind the heaviest components and turning the oil into tar. On rocky shores with surf, the tar will erode away from the wave action, and biological communities will return rather quickly. In marshes, however, oil can sink down below the surface and remain for many years. Oil accumulated in marsh sediments undergoes some microbial breakdown, but it is slow. Low-energy environments like marshes are the most vulnerable and show the slowest rates of recovery from oil spills. Effects of a rather small oil spill in Falmouth, MA in the late 1960s were seen to last for a decade by a team of scientists from the nearby Woods Hole Oceanographic Institute. It is seldom that a spill occurs right in an area that has been intensively studied prior to the spill. Fiddler crabs were particularly sensitive, and were still affected after seven years. The oil affected their burrow construction – the burrows did not go straight down, but leveled off to a horizontal plane. While this was not a problem during the summer, when winter came the crabs were not below the freezing zone of the marsh as they should have been and froze to death. Benthic communities took about a decade to return to normal. After 30 years, some abnormalities still are noted in fiddler crab burrows in the oiled areas.