The earthcache is located within Salisbury Beach State Reservation. The beach is open from dawn to dusk; night caching is not allowed. The Reservation is a Massachusetts DCR facility so there is a day use entrance fee between Memorial Day weekend and Labor Day and on weekends between Labor Day and Columbus Day.
This is an earthcache so there isn’t a container to find but instead you discover something about the geology of the area. To log this cache as a found, you will visit two locations in the Reservation and then provide answers to a few questions. The overall terrain rating is a "1" because you can complete the earthcache while on pavement and the boardwalk. Please stay off the dunes and only use the boardwalk. The dunes protect and stabilize the beach and walking on them can kill the plants.
Barrier Beach
Salisbury Beach is a barrier beach which extends 3.8 miles from south to north along the Atlantic Ocean from the Merrimack River to the New Hampshire border. A barrier beach is a narrow and elongated beach situated parallel to the shoreline. The beach provides a barrier between the mainland and adjacent nearshore wetland, such as a salt marsh or mudflat and marine waters offshore. The barrier beach system is comprised of several distinctive topographic elements: coastal beach, coastal dunes, and a salt marsh. This extensive barrier beach system plays a critical role in the protection of the Merrimack River estuary, along with associated salt marsh habitat, dune preservation, and habitat for threatened and endangered species and other wildlife.
Barrier beach topographic elements
(click image to view the Salisbury Beach barrier beach)
Salisbury Beach was created by sediments deposited by glaciers as they melted and receded to the north over 15,000 years ago. As it receded, the glacier left bedrock deposits which are present in small areas at the southern part of the beach, near the mouth of the Merrimack River. The source of the sand at the beach was historically a paleodelta deposited offshore as the glacier receded.
The development of the barrier beach began during the receding of the glacier. First the sea level rose significantly above coastal lowlands and then the land rebounded and became elevated higher than average sea levels. As the sea rose, it eroded glacial deposits offshore which formed the foundation of the barrier beach. This underlying foundation consists of glacio-marine clay which is located at depths of 40 feet or more. Sand and gravel carried along the shore by waves and currents subsequently accumulated on top of the clay to form a spit. The area between the spit and the mainland was mostly open water. Over time, the sea-level rose and the spit continued to enlarge and migrate westward. The protected bay behind the spit filled in with sand, became shallow and developed into a salt marsh.
Cross section of a barrier beach system
The barrier beach geology is a dynamic process due to the storms, tides, and currents. The waves attack the beach and dune face. Sand is then transported in an offshore direction to build sandbars and is moved up the coast by currents. The decreased depth of the offshore area causes waves to break further offshore and away from the dune face. Less energetic waves, consequently, directly hit the beach and dunes. Dune vegetation takes root to provide stability through its root system that holds the sand in place and by trapping windborne sand particles blown from the dry portion of the beach, increasing the volume of sand in the dune. The sand dunes protect inland areas and they supply sand to the adjacent beach system which increases its ability to dissipate storm waves. By absorbing much of the force of the waves, dunes provide protection to landward areas from storm damage and flooding.
The sand dunes at Salisbury Beach are moving westward with a motion similar to that of a bulldozer tread: a rolling, “going over itself” motion. Some natural factors, such as rising sea level, make this process inevitable, while others, such as littoral drift and dune vegetation, make it a relatively slow process. Storms can create changes very quickly. However, human activities also accelerate this process. People, with their desire to visit or live on the beach, often destroy the very resource that attracts them and the resources that provide storm buffering and flooding protection.
Questions
To get credit for this earthcache, you need to visit two locations within the Reservation and then send me the answers to the questions below through email or the Message Center. You don't have to wait for a response from me after you send the answers. You may log this as a find online as soon as you send in your answers.
1) At the posted coordinates you will find a sign with information about the area. Using information found on the sign, list the eight types of plants that can be found growing in the dunes and in the protected areas away from the open beach.
2) While standing at the Stage 2 coordinates, observe the area around you and answer the following questions:
a) Which of the three topographic elements that make up a barrier beach can you see?
b) Identify some of the things you see around you that look like they are preserving or protecting the dunes?
c) Explain how those things protect the dunes?
3) Using the information you have learned about a barrier beach system, explain how a rise in sea level could change the barrier beach.
4) Send me the answers before you log the earthcache as a found online.
5) Include a photo of you and/or your GPSr standing at the Stage 2 coordinates.