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What You Will Do on Day 4
This field trip covers selected locations along the Connecticut River in western Massachusetts from the French King Bridge (MA Route 2) south to Turners Falls, MA. Images taken from the top of Poet's Seat Tower (Rocky Mountain) in Greenfield are also included. Excerpts from USGS maps (Millers Falls and Greenfield Quadrangles) from 1894 and 1941 are included and referenced.
The purpose of this trip is to visit locations that exhibit physical evidence demonstrative of the Connecticut Valley's geology. Specific stops were selected based on easily seen features that can be readily tied to broad concepts (e.g., Plate Tectonics) while providing information on specific topics (e.g., glacial till). These sites are also scenic and visiting them makes for an enjoyable afternoon. This field trip, therefore, focuses on that portion of the present-day Connecticut River that bypasses an obstacle (delta) created by the Millers River as it emptied into Glacial Lake Hitchcock between 14,000 YBP and 12,000 YBP. A brief geologic history of the Connecticut River Valley is available on this site (see links at left) and provides additional background to that presented here.
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What You Will Need For Day 4
• Drinking Water
• Snacks
• Extra Socks
• Rain Gear
• Sun Block
• Insect Repellent
Fees (per person):
• $3 - Admission (Members Free)
• $10 - Weather Forecasting Workshop,
Balloon Launch, & Instrumentation Tour
• $5 - $10 for lunch
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Field Trip
Millers Falls Quadrangle
French King Bridge
Stop #1
(~45 minutes)
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IMAGE 1 - Connecticut River, Looking Northeast, from the French King Bridge
Stephen C. Daukas, April, 2006
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The French King Bridge provides a crossing for MA Rt. 2 (Mohawk Trail) over the Connecticut River, just north of the confluence with Millers River (FIGURE 1 at right - Route 2 shown in red). This location marks the start of this field trip.
Millers River flows generally North to empty into the Connecticut River at this location. This river's progenitor created a delta in Glacial Lake Hitchcock south of its present location. The shape of the delta is, in fact, deltoid. One can imagine the Millers River repeatedly pivoting from the south as far north as its present location, and back again to its southern extreme, while depositing sediments that nearly crossed the entire width of the glacial lake.
We will start at the parking area located at the western end of the bridge (left side of FIGURE 1). There is a parking area for the adjacent public park and trails at this end of the bridge, but do be mindful of traffic - Massachusetts does have the occasional aggressive driver!
CAUTION! DO NOT attempt this hike during winter months, nor during or shortly after rain. We will be descending beneath the bridge's superstructure at the southeast corner of the lot (Northwest corner of bridge) - there are no marked trails here - I suggest you keep to the narrow paved runoff channel along the side of the bridge until you are beneath the bridge. The terrain here is steep (and steepens as elevation drops over 80 feet), covered with leaves and grasses, loose soil in spots, is slick when damp, and footholds can give way in some areas. You will also likely encounter broken glass. Wear proper foot ware and take your time! Let others know of your itinerary for the day. DO NOT TRAVEL ALONE!
Also keep in mind that, as the graffiti beneath the bridge attests, you may encounter other visitors during your descent.
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FIGURE 1 - Millers Falls Quad, NW
USGS Topographic Map, 1941
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IMAGE 2 - Glacial Till
Stephen C. Daukas, April, 2006
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IMAGE 3 - Cobble & Bedding Layer
Stephen C. Daukas, April, 2006
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Once beneath the bridge...
This bridge in rooted in coarse conglomerate and crosses the gorge cut by the river after the lower portion of Glacial Lake Hitchcock drained. The Connecticut Valley Border normal fault (see Background) is also coincident with the river in this location. That is to say, the river follows this fault southward, flowing beneath the French King Bridge, until it detours to the west leaving the fault to continue along a SSW heading.
Digital images taken beneath the bridge of the West bank of the river (IMAGE 2) clearly show poorly sorted conglomerate (glacial till) varying is size from cobbles, to sand, but also displays layering of finer materials (fine sand) in distinct units. Occasional slaty layers (phyllite) lie at lower elevations. These slaty layers appear to lie at an unconformable angle to the previously mentioned fine layers higher in elevation, with dip and strike similar to the exposed layers at the present elevation of the river, however conglomerate does lie beneath this and other bedding planes. Closer inspection shows that the strata is not consistent among samples and the phyllite is just another component of the till. At first glance, the conglomerate looks fairly frangible, however while gathering some samples required careful handling, others were surprisingly difficult to obtain with the rock hammer.
IMAGE 3 shows the phyllite sample taken from the till. The original location (top left of hammer) shows the "bed" from which the sample was taken. The sample (lower right of the hammer) was collected using the rock hammer with some effort. The sample shows a slightly wavy glossy/shiny luster consistent with the intermediate stage between slate and schist. As can be seen in IMAGE 2, this sample is but one of many random components of the conglomerate including rose quartz, phyllite, etc.
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IMAGE 1 was taken from the top of the bridge looking NE (upriver) and shows the rather narrow structure of the valley in this location. Dipping strata can be seen on both sides of the river bank (at waters edge) with similar strike and dip to that found beneath the bridge (dipping down to the left in the image). The CT Valley Border normal fault is along the West (left) bank of the river from this view. IMAGE 4 is a view from the bridge looking SE (down river). Millers River enters the CT River upstream along this bank (IMAGE 4A) where mixing of the two can be easily seen. The normal fault is crossing the river at this location (approximately mid-river) trending toward the SE bank of the river from this view (left side of IMAGE 4), and the CT River makes a 90° bend to the West (right) from this view. The bend in the CT River at this location marks the northern edge of the Montague Delta that prograded into Glacial Lake Hitchcock from the Millers River prior to 12,000 YBP. This delta consists of coarse deposits and bedrock, the northern edge of which rises from the Southern bank of the river (directly behind the river in IMAGE 4).
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IMAGE 4A - Millers River joins CT River
Stephen C. Daukas, April, 2006
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IMAGE 4 - Connecticut River Diverts to the West (right) Around Montague Delta
Stephen C. Daukas, April, 2006
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The bend in IMAGE 4 also marks the location of a deeply eroded structure beneath the present level of the river. This pothole is approximately 120 feet deep and coincides with the location of the Border fault previously described.
We will follow the river's course downstream on our drive to Barton Cove, our next stop on the field trip.
Greenfield Quadrangle
Barton Cove
Stop #2
(~3 hours, including lunch)
Turn right out of parking area onto Route 2 West. Depending on the time of year, you will be able to see portions of the CT River to the South (your left as your travel West on Route 2). Continue for ~4 miles to the Barton Cove Recreation Area (Northeast Utilities) - turn left onto the access road and continue to the (small) parking area. Restrooms are located here, as well as several picnic areas and an information station. The distal picnic area of the peninsula may serve as a good location to have lunch.
The access road has taken you approximately 1/5th the length of the Lily Pond Formation, the sandstone bedrock nick point over which the CT River once flowed. This stop will cover the entire length of the formation, both ancient water falls, as well as the final course of the river at the distal end (the ancient river course prior to glaciation). However, the majority of time will be spent at the proximate waterfall location (Site #1) as access is much easier and far safer.
Once the lower portion of Glacial Lake Hitchcock drained, the CT River began to flow. As previously noted, the river's flow was diverted around the Montague delta as its elevation was now higher than that of the river's, and it was composed of resistant material. As the river wound its way around this delta (Horse Race - FIGURE 3 above), it encountered the Lily Pond Formation, which it would have normally passed by to occupy its ancient river bed (the Narrows in FIGURE 2 and FIGURE 3 above) if not for the fact that this path was blocked with deltaic material. Thus, the river was forced over the sandstone ledge.
After some period of time, perhaps more than 1000 years, the obstruction at the Narrows weakened due to basal sapping eventually giving way and allowing the river to occupy its ancestral channel. Before that time, however, two deeply eroded cuts in the sandstone bedrock were carved by waterfalls. The plunge pools at the base of these ancient waterfalls were called lily ponds, clearly visible in FIGURE 3 prior to the formation of present day Barton Cove by flooding, and lent their name to the sandstone bedrock formation.
Lily Pond Formation - Site #1
Access to Site #1 is along the north (proximate) side of the cliff. Walk the access road toward distal end of the peninsula and depart paved access road for the first trail on right (~20 yards from parking area). This trail is short, but offers a good view of the site and terminates at the location from which IMAGE 5 was taken (IMAGE 6).
IMAGE 5 offers an idea of the size of the waterfall and the plunge pool (now submerged) at its base. Vertical cliffs rise in elevation from the current water level 30-40 feet, with steep slopes above the cliff edge rising an equivalent distance. Standing atop the site is reminiscent to standing atop a flooded quarry.
IMAGE 6 shows the sandstone bedrock of the Lily Pond Formation at the NE edge of the plunge pool (a small peninsula between the plunge pool and Barton Cove). The dip and strike of this formation is N 40 E, 36 SE, with the dip towards the plunge pool. IMAGE 6A shows the bedding at this location. IMAGE 6B show a sample taken from this formation.
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IMAGE 5 - Site #1, Looking Southeast
Stephen C. Daukas, April, 2006
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IMAGE 6 - Exposed Sandstone, NW of waterfall
Stephen C. Daukas, April, 2006
The sample shown in IMAGE 6B (at right) shows thin strata of fine sand. The sample was hammered from the outcrop (IMAGE 6 above), but differs very little from weathered "chips" scattered across the location: color & texture of sample does not differ from that of exposed rock.
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 IMAGE 6A, Lily Pond Formation Sandstone
Stephen C. Daukas, April, 2006
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 IMAGE 6B, Sample taken at IMAGE 6 location.
Stephen C. Daukas, April, 2006
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Retrace the trail back to the paved access road, turn right and walk past Site #1. Take next trail on right (enter to the right of the split-rail fence). This trail follows the top of the SE wall of Site #1.
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IMAGE 7 - Fluvial Erosion SE Wall
Stephen C. Daukas, April, 2006
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IMAGE 8 - SE Wall, Looking up-slope
Stephen C. Daukas, April, 2006
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This trail is above the vertical SE wall of the waterfall (right side of trail) with higher elevations to the top of the nick point (left side of trail). Approximately 30 yards along the trail to your right, you can see a fluvial feature in the bedrock wall of the nick point (IMAGE 7). The rounding of the rock in general, as well as the concave channel in particular, can be clearly seen. Looking SE up to the top of the formation at this location (IMAGE 8) shows more strata of the barrier overlain by conglomerate (large boulder in upper left of image). While IMAGE 8 gives a sense of the angle of the slope, looking up at these large outcrops in situ instantly gives one pause with the realization that the image was taken on what is essentially a talus slope. Total change in elevation from top of nick point to water level is approximately 80 feet.
Looking due south from this same location shows a typical outcrop of resistant sandstone set above a channel terrace (just visible at left edge) dipping to the right and perched approximately 30 feet from the final vertical face of the nick point (IMAGE 9). The entire SE section of the nick point is composed of vertical walls terminating above terraces at differing elevations with channels running throughout.
Continuing along the trail will lead to an observation platform. Descend along the trail to the left of the platform - be careful of the steep slope along this portion of the trail - and then up the opposite slope until you reach the base of an outcrop.
This location is located well below (and to the right) of the wooden stairs shown in IMAGE 9, approximately 15 feet above present water level.
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IMAGE 9 - Site #1 Upper Cliff, SE Wall
Stephen C. Daukas, April, 2006
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This location of site #1 is perhaps the most interesting of Stop #2. The outcrops in this general location display a melange of strata (lacustrine and playa strata, gray shale bounded by lighter color beds above and below, beds of breccia composed of dolomitic siltstone, fine sandstone and dark mudstone). While individual sections can be identified, understanding how the chaotic layering of sections relate to one another takes some time. Keep in mind that this location has been subjected to both tensional and compressive forces (see background).
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IMAGE 10 - Melange @ SE Wall Base
Stephen C. Daukas, April, 2006
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IMAGE 11 - Melange @ SE Wall Base
Stephen C. Daukas, April, 2006
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IMAGE 12 - Cycle @ SE Wall Base
Stephen C. Daukas, April, 2006
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Shallow lacustrine strata and playa deposits tend to be reddish in color and fairly massive while deeper water lacustrine deposits trend towards fine laminations which are dark to black in color. IMAGE 10 - IMAGE 12 show deposits that have weathered to gray, yellow and white.
The deformation apparent in the images is complex and include a variety of folding (including recumbent) at varying intensities. The melange results from a combination of thrust faults and folding of the ancient syncline in this area (see background). After studying the outcrop for a period of time, one can begin to make out the pattern in the outcrop that can be best described as being similar to that of ribbon candy.
Looking at the various elevations at this site, we begin to get a feel for the complex geology where fine-grain beds (lacustrine-based shales) interbed laterally with alluvial conglomerates (principal of lateral continuity). At our current lower elevation (at an earlier period) from the Montague delta that prograded into Glacial Lake Hitchcock (principal of superposition), it is clear that we are looking at older bedrock. This formation precedes glaciation and the subsequent formation of the glacial lake. The age of this formation raises a question regarding the ancient location of the river at this location: Why did the river cascade over the formation at this location rather than occupy its original course? Recall that this formation is covered by conglomeritic strata (IMAGE 8) which also filled the rivers original channel. As previously noted, it took some time for this "plug" to erode allowing the river to occupy it present (and ancient) channel.
Retrace your path to the left of the outcrop just examined, heading up slope towards the wooden stairs picture in IMAGE 9. Take the terraced stairs to the landing, then bear right and continue along the trail (heading south) to the top of the ridge. This trail rejoins the access road at the top of the ridge.
Lily Pond Formation - Site #2
Depart the access road to your right (NW) onto the trail marked with white diamonds (attached to tree trunks at eye-level). Access to Site #2 is along this trail (10 minute walk). This trail meets the NE side of the second waterfall and leads around to the SE side while following the general outline of the cliff (IMAGE 13). Barton Island (see FIGURE 2) is visible through the trees in IMAGE 13, as well as the far shore of Barton Cove. A note of caution is in order: Site #2 is not as accessible as Site #1 and, as can be seen in IMAGE 14, the slopes are steep and covered in leaves, mosses, and ferns. I do not recommend a descent, nor do I recommend getting too close to the edge.
This trail along the vertical SE wall (IMAGE 14) affords a good view of Site #2 from the several paths leading from the trail to the edge of the cliff. This location is not quite as large as Site #1 and the walls at this location display very little terracing. As this site is geologically similar to that of Site #1, we will move on to the distal portion of the formation.
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IMAGE 13 - Approach to Site #2
Stephen C. Daukas, April, 2006
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IMAGE 14 - Upper Cliff, SE Wall
Stephen C. Daukas, April, 2006
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Continue along the same trail south to the end of the formation (10 minutes). You will arrive at a picnic area with restrooms.
Lily Pond Formation - Site #3
Walk toward the split-rail fence at the south end of the picnic area. This is The Narrows, the channel (IMAGE 16) once blocked by conglomerate that caused the Connecticut River to spill over the ridge you just hiked, incising the two ancient waterfalls (Site #1 and Site #2). Once the conglomerate filling the channel was cleared, the waterfalls ceased. IMAGE 15 shows the start of The Narrows where the Connecticut River passes into Barton Cove (through IMAGE 16) to the right (see FIGURE 2 & FIGURE 3).
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IMAGE 15 - Entrance to The Narrows
Stephen C. Daukas, April, 2006
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IMAGE 16 - CT River Looking South
Stephen C. Daukas, April, 2006
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This may be a good time to have lunch. When ready...
Walk to the southeast end of the picnic area overlooking the river. Locate the path to your left and follow it up to a series of paved picnic areas. Follow the paved access road back to the parking area (10 minutes). We will continue to parallel the Connecticut River as we drive to our next stop.
Greenfield Quadrangle
Turners Falls
Stop #3
(~1 hour)
Follow the access road back to Route 2. Turn left out of Barton Cove onto Route 2 West. Follow Route 2 West for ~1 mile to intersection (Turners Falls Bridge to left). Continue on Route 2 past the intersection and turn left into the second, lower entrance to the rest area (immediately west of intersection) overlooking Turners Falls Bridge and the falls beneath. Be careful of traffic when making this turn!
CAUTION! This stop requires great care because of traffic on Route 2. Remain alert for vehicles in both the parking area as well as along the roadside. Look in all directions before you move around!.
Turners Falls - Site #1
Turners Falls is directly beneath the bridge (IMAGE 19) and is the foundation for the dam built upon it. The dam was built to raise water levels in order to supply a power canal, and also flooded Barton Cove upstream (refer to FIGURE 2 and FIGURE 3). IMAGE 18 shows the Turners Falls Sandstone located along the NE bank of the Connecticut River (to the left of IMAGE 19) below the dam (blue canisters in IMAGE 18 are 55 gal drums).
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IMAGE 18 - Turners Falls Sandstone, NE bank
Stephen C. Daukas, April, 2006
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IMAGE 19 - Turners Falls viewed from Rest Area
Stephen C. Daukas, April, 2006
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Trails located to the south of the rest area (on opposite side of fence) lead down to the Connecticut River. We will not fully descend these trails during this stop due to recent precipitation. CAUTION! Descending to the river is not recommended due to potentially unannounced discharges from the Falls River Dam, as well as the steepness of the trails leading back to higher ground, and to safety.
Because this location is one of only a handful in the world where you can find armored mud balls, I have included an image taken at this location along a trail descending approximately half way to river level (IMAGE 20). This image shows what could have been two armored mud balls embedded along the side of the descending trails. This section of the trail contained a line of five (5) forms of similar size (15cm - 20cm). These features have what look like exfoliation layers and are in line (spatially) with pillow lava shown in Image 21 below. A sample was taken (after being accidentially knocked loose by a friend - never travel alone - as he slid down the trail after loosing his footing) for examination. Initial examination of interior portions of that sample show faily uniform distribution of clasts, which suggests these may well be mud balls, but more detailed examination has yet to be done.
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IMAGE 20 - Armored Mud Balls (?) below rest stop
Stephen C. Daukas, April, 2006
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Turners Falls - Site #2
Across Route 2 from the rest area is a road cut that exposes an excellent sequence useful for discussing relative dating. In order to view the features of the outcrop, you must cross from the rest area to the opposite side of Route 2. This is best done with great care at the traffic light. Stay well away from the paved roadway and be conscious of where you are relative to Route 2! Look away from the outcrop and in all directions before you take a step!
The Turners Falls Sandstone (IMAGE 24) is visible at the SE end of cut (to the right from this view). This is the same sandstone seen in IMAGE 18, with the same dip and strike. Beneath the sandstone (moving right to left) is the top layer of a lava flow (red vesicular) followed by (IMAGE 23) the middle portion of the flow containing sills followed by (IMAGE 22) columnar joints at the base of the upper flow. To the left (IMAGE 21) is the top layer of another lower flow followed by pillow lavas (bore hole, far left of image). Of note in this sequence is that pillow lavas form underwater!
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IMAGE 21 - Pillow Lava
Stephen C. Daukas, April, 2006
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IMAGE 22 - Columnar Joints
Stephen C. Daukas, April, 2006
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IMAGE 23 - Volcanic Sills
Stephen C. Daukas, April, 2006
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IMAGE 24 - Sandstone
Stephen C. Daukas, April, 2006
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These images are arranged in the order in which they appear in the outcrop as viewed from the rest area. IMAGE 21 is on the left (NW) of the outcrop, and IMAGE 24 is on the right of the outcrop (SE). Not shown in three of the images are multiple bore holes located in the various strata. One bore hole is visible in IMAGE 21 (enlarged view). The cores taken at these locations are used for paleomagnetic studies.
Return to the rest area for departure to Stop #4.
Greenfield Quadrangle
Poet Seat Tower
Stop #4
(~1 hour)
Turn left onto Route 2 West and continue to traffic light. Turn left at lights and follow Route 2 (Mohawk Trail) for ~1.5 miles. Turn left onto Haywood Street, then right onto Parkway St. (follow blue signs to Poet Seat Tower). The entrance to the park will be on your left. There is a small parking area at the base of the access road (gated) that leads to the top of the mountain and the Poet Seat Tower (10 minute walk).
This stop provides a good view of the valley in this area and provides a context for the sites visited during this field trip. Correlating views in a given direction to topographic maps of the area (e.g., FIGURE 2) not only provides a great opportunity to appreciate scale and place the sites visited into a "big picture", but also allows one to interpret how the "bits and pieces" of the field trip fit together to "expose" the geology of the area. We will survey the valley in a clockwise direction, beginning with Turners Falls.
Poet Seat Tower is located atop the basalt ridge (Deerfield basalt) that forms the west bank of the present-day Connecticut River. IMAGE 25 is looking upriver at the nick point and dam at Turners Falls (behind smoke stacks). IMAGE 25 also shows the location of the rest stop (Stop #3) where we viewed the road cut through the same basalt formation. The bend in the river (at the rest stop) marks the location where the river once continued northwest along Route 2 past the distal end of this ridge (Canada Hill) where Fall River passes beneath Route 2, and then down the left side of the ridge (through White Ash Swamp, FIGURE 2 & FIGURE 3). The earlier course (~11,000 YBP) was a consequence of the Montague Delta blocking its original channel.
IMAGE 26 is looking NE and shows both the Connecticut River and the Power Canal made possible by the dam at Turners Falls that raised water level to flood the canal, as well as Barton Cove. IMAGE 27 is looking generally east and shows the Montague Delta formed by Millers River (the Bronson Hill uplands are in the distance). IMAGE 28 is looking SSE at Mt. Toby (distance, center), one of the many locations where ice contact features (eskers and kettles along a kame terrace) can be found.
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IMAGE 25 - Turners Falls
Stephen C. Daukas, April, 2006
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IMAGE 26 - River and Power Canal
Stephen C. Daukas, April, 2006
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IMAGE 27 - Montague Delta
Stephen C. Daukas, April, 2006
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IMAGE 28 - Mt. Toby
Stephen C. Daukas, April, 2006
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IMAGE 29 - NE along Basalt Ridge
Stephen C. Daukas, April, 2006
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IMAGE 30 - Lowlands West of Ridge
Stephen C. Daukas, April, 2006
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IMAGE 31 - Mts. Tom and Holyoke
Stephen C. Daukas, April, 2006
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IMAGE 32 - Mt. Tom Gravel Pit
Stephen C. Daukas, April, 2006
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IMAGE 32 looks SW down the ridge. A gravel pit is visible just NE of Mt. Tom. Gravel and sand pits are not uncommon in the area because of both lacustrine and glacial deposits. IMAGE 31 shows Mt. Tom and Mt. Holyoke (Mt. Holyoke is distal). The Connecticut River passes between the end of our basalt ridge and Mt. Tom, then through the gap between Mt. Tom and Mt. Holyoke. The gap between Mt. Tom and Mt. Holyoke is the site of the meander cutoff (oxbow) described in the background section. IMAGE 30 is looking SE over Greenfield and shows the lowlands where the Connecticut River once flowed. IMAGE 29 is a view NE along the basalt ridge that terminates at Canada Hill, just west of Stop #3 (rest stop) where we viewed a road cut of this basalt. White Ash Swamp is located in the lowlands proximate to the left side of the ridge from this view.
This completes our tour of the area for the day.
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