Deer Island, Boston Harbor, Massachusetts
Earthcache
GPS Coordinates: N42 21.287 W70 57.621
WARNING: Obey posted signage and open flames are restricted in some of the areas. Please stay on designated trails because rising tides may trap the unwary visitor who leaves the pathway and enters the intertidal area at low tide. Dogs must be kept on leash at all times.
Deer Island is one of many islands that can be found within Boston Harbor, Massachusetts. Although originally an island, the New England Hurricane of 1938 caused enough shoreline erosion to fill Shirley Gut located between Deer Island and Winthrop, connecting the island to the mainland. However, the name Deer Island has remained.
Boston Harbor is part of the Boston Basin. During the Pleistocene Ice Age, which ended about 12,000 years ago, ice sheets covered New England and much of North America. The ice sheets were not stationary but advanced and retreated, each time grinding, scouring and eroding material from the bedrock beneath. As the ice sheets melted and retreated in the New England area, Boston Basin became an outwash plain which filled with this eroded sand, gravel, silt and clay, also referred to as glacial till. Much of this glacial till was deposited as large asymmetrical, elongated smooth-sloped mounds called drumlins. In profile, these drumlins look like upside-down teaspoons. The drumlins can vary widely in size with lengths from 0.6-1.2 miles (1-2 km), widths from (400-600 metres) and heights from 50-100 feet (15-30 metres). Characteristically drumlins form in the direction of ice flow, with their long axes roughly parallel the direction which the ice sheets moved. In addition, the glacier side of the drumlin is typically high and steep while the lee side is smooth and gently sloped.
Drumlins may occur as scattered single hills or in clusters called ‘swarms’. Boston Harbor and its islands are part of a drumlin ‘swarm’, and are part of the only drumlin swarm in the United States that intersects a coastline. However, not all of the islands in the basin have that classic elongated drumlin shape. Geologists believe this is because the area was subject to two separate periods of glacial advance and retreat, and that many of the islands are in fact made up of more than one drumlin.
The ice sheets covering North America could be several thousand feet thick and the sheer weight of this ice literally caused the land to sink. As the ice sheets melted, the land began to rise or rebound because it was no longer under such weight. This rebound meant that relative sea level was much lower than it is today and the Boston Harbor Islands would have been a set of hills on a grassy plain rather than islands. The land in the region eventually stopped rebounding but sea level continued to rise due to melt water input from the ice sheets, and this grassy plain was drowned or submerged leaving the familiar islands that are visible in Boston Harbor.
Deer Island is also part of the Boston Harbor Islands National Recreational Area, a 1600 acre series of islands and mainland parks. Many of these islands provide important habitat and nesting grounds for migratory birds. Deer Island itself is steeped in history. It was an internment island for Native Americans in the late 1600s, a landing point and holding area for thousands of Irish refugees fleeing the Potato Famine in the 1800s, and housed a prison between the 1880s and 1980s. Today, Deer Island includes a park which offers trails, picnicking and fishing, but is best known as the location of the Deer Island Waste Water Treatment Plant (WWTP).
The Deer Island WWTP treats about 365 million gallons of waste water each day from 43 cities and towns in the Boston area. While the plant, and its 12 150 foot tall sludge digesters, is visible from many points in the harbor, a man-made berm blocks the view from the nearby community of Winthrop. Air scrubbers and carbon adsorbers remove odors and volatile organic compounds from treatment process "off-gases".
The Deer Island WWTP is the centerpiece of the Massachusetts Water Resource Authority (MWRA) and its program to protect Boston Harbor against pollution from metropolitan Boston’s sewer systems. Waste water passing through the Deer Island WWTP undergoes primary and secondary treatment which results is over 85% pollution removal. Before the treated effluent is discharged into the deep waters of Massachusetts Bay, it is also disinfected to kill bacteria and dechlorinated so chlorine levels do not threaten marine life. Deer Island also self-generates 26% of its electricity needs and more than half of the Island’s energy demand is provided by on-site, renewable generation. For example, methane, a by-product of the treatment process, is captured and piped to boilers to generate heat for the facility, while 736kW of photovoltaic systems are installed throughout the plant and two 600kW wind turbines generate over 2M kWh per year.
For those who are interested, tours are of Deer Island are offered but advanced reservations are required and can be made by contacting the Deer Island Tour office at (617) 660-7607.
Earthcache Questions:
Q: What is the origin of the word drumlin?
Q: What are the classic characteristics of a Drumlin? Observe Deer Island and the other islands in the area. Does Deer Island retain these classic features?
Q: The berm that blocks the view of the treatment plant from the nearby town is man-made but was built by relocating a drumlim that originally existed on the island. Does this berm have the same features as a real glacial drumlin? Explain why or why not.
Learn more:
National Parks Service
Massachusetts Water Resource Authority (MWRA)
A First to Find will be awarded a Gulf of Maine Council limited edition geocoin!, and has been found!