Geology of Martha's Vineyard

Martha’s Vineyard was formed during the last glacial period, the Wisconsinan glaciation. 

Two glacial lobes, the Buzzards Bay Lobe and the Cape Cod lobe formed Martha’s Vineyard.  As the glaciers move along the land, they pick up large boulders and debris. When the glacier began receding or melting, they left behind large boulders and debris.  The heavy boulders and debris were dropped at the farthest place the glacier made it to, called the end moraine.  As they melted, rivers of melted water carried debris creating the outwash plains.  See the map below. 

 http://pubs.usgs.gov/of/2008/1288/html/imagepages/figure2.html

We attempted to make a time-lapse simulation of a glacier melting.  We froze rocks and debris in mold or casts.  It isn’t quite accurate because glacier debris was not spread through-out the cast.  

To watch the video, click here.

The clay cliffs, such as the ones found in Aquinnah were created by the pressure or weight of the glacier.  The clays were under the sea bed, but were forced upward.

We squashed clay to mimic the upward thrust.

Resources

Oldale, R.N. (2001). Cape Cod, Martha’s Vineyard, and Nantucket: The Geologic Story.  Yarmouth   Port, MA: On Cape Publications. 

Cooper, Doug.  “Understanding the Island’s Geology in 3 Walks.” Presentation through the Adult and Community Education of Martha’s Vineyard, MA, 7-26, 2016.