Highlights of Bottom Processes

The time series movie shows changes in the sea floor.  A major process illustrated in these photographs is the resuspension of sediments caused by currents associated with waves. Note the episodic increases in suspended material which occur during times of large pressure standard deviation and that obscure the bottom from view (for example on September 3 and September 18). The sea floor in this region of Massachusetts Bay is gravel and coarse sand. However, there are patches of fine-grained sediment nearby, and a fine veneer of fine sediments accumulates on the sea floor during non-storm times. These fine sediments are resuspended by the strong oscillatory currents associated with surface waves. In some of the events, a small rock or boulder shifts position on the sea floor.   For example, a cobble located about 1/3 of the way from the west (left) edge of the frame (approximately in line with the compass housing) shifts from east to west (right to left) on July 24.  Throughout the period, small shells can be observed moving in the field of view.  These changes can be most easily observed by using the slider on the viewing bar to quickly view the sea floor at different times.  Other observations and modeling suggest that fine sediment resuspend during storms in this region of western Massachusetts Bay is transported to the south toward Cape Cod Bay, and offshore into Stellwagen Basin (Butman and Bothner, 1998). These regions are the long-term depositional sites in the Massachusetts Bay region.