Stop 2: Harbor and Barrier Spit
Walk The Trail:
Map of Nature Trail

Map showing Nantucket Harbor and Coatue Barrier SpitFrom the top of the cliffs overlooking Nantucket Harbor, you can see the barrier spit, Coatue, in the distance. Formed over 6000 years ago by wind, waves, and ocean currents, Coatue protects Nantucket Harbor. The harbor is a shallow embayment resulting from this protection, and home to a wide variety of sea life, including horseshoe crabs and the bay scallop.

The cliffs are a result of loose materials deposited by meltwaters from the glaciers that formed Nantucket about 18,000 years ago. Nantucket Island, Martha's Vineyard, and all of Cape Cod were formed at the maximum extent - or terminal moraine - of the Laurentide ice sheet, during the Wisconsinian glacial stage. The mile-high glacier, acting like a gigantic bulldozer, scraped and pushed tons of material southward during its advance. As the climate warmed, the melting ice sheet dumped its load of sands, gravels and rocks in place, forming Cape Cod and the Islands.

 

Map of Cape CodWith water frozen up in the giant ice sheets, sea level was 100 meters lower than it is today. Evidence for this is provided by the teeth and bones of now-extinct mastodons and mammoths that have been dredged up from the shallow seas surrounding Nantucket. Some of these fossils are only 10,000 years old.

Sea level rose rapidly as ice melted, at rates up to 15 meters per 1000 years. Nantucket and Martha’s Vineyard became islands (separated from the mainland) around 4000 years ago, although sea level continued to rise at about 1 meter per 1000 years until recently. Sea level has risen around 0.3 meters (1 foot) in the last 100 years, in part due to the increased concentrations of greenhouse gases in the atmosphere.

 
 
previous stopnext stop
Back to the start of the trail Harbor and Barrier Spit Stop 3: Beach Erosion The Ospreys Mowing and Succession Stop 6: How Plants Reproduce The Tangled Web of Vines Plants by the Pond Hidden Treasures at the Pond Wrack Lines at the Beach Folger's Salt Marsh

     The Nantucket Field Station Virtual Nature Trail is a joint effort of the following departments: Biology, Computer Science, Earth & Geographic Sciences, and ECOS. UMass Boston Home Page

     All images are (c) the photographers or UMB and may not be reproduced without permission.