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What You Will Do on Day 6
This field trip will visit The Cape Cod Canal where we will get better oriented to the history of the canal at the Visitor's Center, and then participate in a guided exploration of the beach at the Canal's East Entrance. This program's focus is on a one-mile section of beach, examining how the continuous changes to the shoreline impact the plants and animals located there.
The purpose of this trip is to become familiar with coastal processes, landforms, and the intertidal zonation in general, and how human development has changed a section of beach adjacent to the Cape Cod Canal.
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What You Will Need For Day 6
• Drinking Water
• Snacks
• Rain Gear
• Extra Socks
• Insect Repellent, Sunblock
• Appropriate Beach Attire
• Appropriate Beach Footware
• Beach Profile Instructions (provided)
Fees (per person):
• $5 - $10 for lunch
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Field Trip
Cape Cod Canal
(~5 hours)
IMAGE 1 - Cape Cod Canal
From: USACE Cape Cod Canal Website
Cape Cod was formed by a warming of Earth's climate that led to the retreat of the Wisconsinan Ice Sheet (see Day 5 of this series, specifically the first section of The Pleistocene Forward) that once covered the area. With the melting of glacial ice, and the thermal expansion of ocean water with the warmer temperatures, came a rise in sea-level that innundated the former coastal plane beginning a continuous process of coastal erosion that has continued unabated for more than 15,000 years.
The Islands of Martha's Vinyard and Nantucket formed at or near the terminal ends of this ice sheet (IMAGE 2 below left). Martha's Vinyard is a terminal morain - a mound or ridge of unstratified glacial till deposited at the maximum extent of an ice sheet. Martha's Vinyard formed between the stationary ends of two lobes of the Wisconsinan Ice Sheet, the Buzzards Bay lobe and the Cape Cod Bay lobe, where the ice melted as fast as new ice advanced. The melting of ice in combination with advancing ice from up-glacier resulted in a converyor-like movement of debris to the stationary end of the ice sheet, where it essentially piles-up (dark pink). Nantucket Island is thought to be a recessional moraine - glacial till deposited during a pause in the retreat of a glacier. Nantucket is located between the Cape Cod Bay and South Channel lobes. Deposits from the South Channel Lobe are exposed on the outer part of Cape Cod (the rest are below water), but the majority of Cape Cod came from deposits by the Cape Cod Bay lobe.
IMAGE 2 - Cape Cop & Islands Moraines, Outwash Plains, and Ice Sheets
From: USGS History of Cape Cod Web Site
As the lobes melted, they did so at different rates (IMAGE 2 above right). The Buzzards Bay lobe retreated first, followed by the Cape Cod Bay lobe, and finally the South Channel Lobe. Because of the order of moraines being deposited from the lobes retreat, meltwater from the South Channel lobe created Glacial Lake Cape Cod impounded by the Sandwich ressional moraine located at the Cape Cod side of the isthmus. The Sandwich and Buzzards Bay moraines come to a point just at the location of the Cape Cod Canal. MA Route 28 and MA Route 6 are located atop these moraines (outline in FIGURE 1 below).
FIGURE 1 - Moraines in relation to Major Cape Roadways
Modified from Mapquest
The Cape Cod Canal was built in the ancient spillway of Glacial Lake Cape Cod that drained the lake water through the valley that today is Buzzards Bay. Sea level at that time was some 300 feet lower than today's due to the fact that so much water was locked in ice.
IMAGE 3 - Cape Cod Canal
From: USACE Cape Cod Canal Web Site
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IMAGE 3 shows the canal cut looking southwest, with the East Entrance from Cape Cod Bay in the foreground. The mainland is to the right, and Buzzards Bay is at the top of the image.
The site of our field trip is visible in the lower left hand corner of IMAGE 3, on the Cape side of the canal. IMAGE 4 (below) is a close-up satellite view of the field trip location with the Canal at top and Cape Cod Bay at right. Visible in IMAGE 4 are several groins that will be visited during the field trip.
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IMAGE 4: Field Trip Location
Stephen C. Daukas, Google Maps
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Site #1 Visitor Center
Visitor Center
USACE Web Site
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This section of shoreline is located adjacent to the Visitor's Center, connected by a path along the side of the Canal. The areas to the right of the trail are not part of the USACE property. Additionally, the destination beach area is a mosaic of USACE, State, and private property.
Several examples of the exhibits located within the Visitor Center are pictured below. Additionally, there are three 15-minute programs covering the history, flora and fauna of the Canal.
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IMAGE 5 - Navigation
Stephen C. Daukas, July, 2006
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IMAGE 6 - Trattic Control
Stephen C. Daukas, July, 2006
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IMAGE 7 - Canal Radar
Stephen C. Daukas, July, 2006
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IMAGE 8 - Marine Life
Stephen C. Daukas, July, 2006
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Site #2 Sandcatcher Recreation Area
As we follow the path to the beach, the scale of the Canal become apparent, especially when ships pass side by side. The Cape Cod Canal is the widest canal in existance at 540 feet. The volume of water that moves through the canal at flood tide is sufficient to scour the entrances thus nearly eliminating the need for dredging.
While examining the beach, we will be sketching and taking measurements to contstruct profiles at three different locations (selected to avoid beach goers). We will be using the parallelogram method described in the WHOI Sea Grant Bulletin available via the web resource links on today's background reading page. Recommended locations are:
P1. in the area of IMAGE 11 - approximately 15 meters south of jetty
P2. in the area of IMAGE 14 - approximately 100 meters south of jetty
P3. in the area of IMAGE 20 - profile to extend into water past the spit
The recommended benchmark/baseline (common reference point) for all three profiles is the dune scarp pictured in IMAGE 26. We will not be setting a permanent benchmark, but will set a temporary marker near the face of the scarp. This scarp is located approximately 15 meters south of the jetty in line with the location from which IMAGE 11 was taken. The first profile (P1), therefore, should begin at this scarp and continue past the low-tide water level for approximately 5-10 meters.
Profiles P2 and P3 will also begin at the dune scarp in their respective locations, however be sure to take a measurement along each profile that lines up with the benchmark (dune scarp) of the first profile, P1. This is best done with two people - one at the first scarp, the other in-line with the profile being taken. The person at the benchmark will guide the second person into an imaginary line bewteen the benchmark location and a distal point on the horizon. The second person notes this point on the profile datasheet for later use as a registration point to compare profiles, and to construct a rough map of the beach. So long as the technique used for siting the benchmark/baseline is consistent and is reasonably accurate, the results will be fine for our purposes.
IMAGES 9 - 12 show the approach to the beach area. IMAGE 9 is a view of the canal from the path, IMAGE 10 is the dune area to the right of the path where it meets the jetty and the beach. IMAGE 11 shows both jetties (with a ~40' boat trversing the canal), and also gives a sence of the beach profile at this location. IMAGE 12 is an image of the cobble-sized beach material adjacent to the down-current side of the jetty. This is showing starvation as the smaller grains have been removed. This image also shows the Supralittoral Fringe where barnacles have encrusted the rocks (see the background reading, specifically Intertidal Zonation).
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IMAGE 9 - Along the Canal
Stephen C. Daukas, July, 2006
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IMAGE 10 - Dunes
Stephen C. Daukas, July, 2006
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IMAGE 11 - Jetty
Stephen C. Daukas, July, 2006
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IMAGE 12 - Starvation at Jetty
Stephen C. Daukas, July, 2006
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IMAGE 13 (below) is a view from the jetty looking south (away from the Canal's East Entrance). The concave shape of the beach is an example of starvation that occurs down-current of a jetty or groin. IMAGE 14 is about mid-way between the jetty and the first Groin and IMAGE 15 is the up-current side of the groin. As rocky as this side of the groin may be, IMAGE 16 shows how much material has been removed from the down-current side of the groin. Close examination of IMAGE 4 (above) shows the location of the first groin located approximately at the bottom edge of the vegetated (brown) area in the satellite image.
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IMAGE 13 - Starvation
Stephen C. Daukas, July, 2006
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IMAGE 14 - Approach to Groin
Stephen C. Daukas, July, 2006
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IMAGE 15 - First Groin
Stephen C. Daukas, July, 2006
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IMAGE 16 - Starvation at 1st Groin
Stephen C. Daukas, July, 2006
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IMAGE 17 and IMAGE 18 (below) show the area proximate to, and down-current from, the first groin. When the composition of the beach in this image is compared to that of IMAGE 15, it is easy to see the relative difference in grain size. Periwinkle dot the cobbles in IMAGE 18, as well as an occasional seaweed. IMAGE 19 and IMAGE 20 shows the changes to the shoreline in the vicinity of the second groin. IMAGE 4 (above) shows the sand beginning to shoal around the end of the groin. IMAGE 20 (below) shows a more recent image of a fully developed sand spit (see the background reading, specifically Figure 3 - Landforms) curving into what was the scoured area (starvation) down-current of the groin. As this form is only fully visible at low tide, it could be referred to as a sand bar, perhaps a proto-sand spit. The scoured area is now acting as a bay, while the original groin is some 30 feet from the low-tide mark. Just to the right of this spit is another groin.
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IMAGE 17 - Starvation 1st Groin
Stephen C. Daukas, July, 2006
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IMAGE 18 - Starvation 1st Groin
Stephen C. Daukas, July, 2006
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IMAGE 19 - 2nd Groin
Stephen C. Daukas, July, 2006
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IMAGE 20 - 2nd Groin
Stephen C. Daukas, July, 2006
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IMAGE 21 (below) show the lagoon formed behnd the sand spit and IMAGE 22 shows several small crabs from this same area of the lagoon. IMAGE 23 is a close-up view of the shallows fringing the spit. IMAGE 24 shows the view towards the jetty from atop the berm (see Figure 1 in the background reading) with the low tide terrace visible to the right of the lower dark line (seaweed). The south jetty of the canal is visible in the diatance, with the longer north jetty crossing the image slightly above.
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IMAGE 21 - Lagoon
Stephen C. Daukas, July, 2006
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IMAGE 22 - Crabs from Lagoon
Stephen C. Daukas, July, 2006
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IMAGE 23 - Shallows of Lagoon
Stephen C. Daukas, July, 2006
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IMAGE 24 - Beach Profile
Stephen C. Daukas, July, 2006
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IMAGE 25 (below) shows the several berm crests along this beach. three or four such berms can be found along different sections of the beach, but two seems to be the norm. IMAGE 26 shows the dune scarp - the terminus of the backshore of the beach - with an increasing density of grasses and scrub moving inland. IMAGE 27 shows a wide-view of the beach looking south from the jetty. Three or 4 berms can be seen as we move from left (water) to right (grasses). IMAGE 28 is a final look over the south jetty of the canal entrance into Cape Cod Bay.
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IMAGE 25 - Beach Profile
Stephen C. Daukas, July, 2006
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IMAGE 26 - Dune Scarp
Stephen C. Daukas, July, 2006
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IMAGE 27 - Profile from Jetty
Stephen C. Daukas, July, 2006
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IMAGE 28 - South Jetty
Stephen C. Daukas, July, 2006
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After the profile data are taken, we can use graph paper to sketch the results. Others can now take water samples at the approximate locations of the three profiles, with one sample being taken from the tidal pool at profile location P3. Samples will be examined using equipment provided. Refer to the Marine Organisms section of today's background reading to help in identification of any organisms in the samples.
This completes day six of the tour. We will return to our hotel, and meet in the hotel lobby for dinner.
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