Inaugural Father James Skehan Geological Field Trip
Geologic Field Trip to Investigate Glacial Features in and around Sudbury, MA
Dr. Ken Galli, Boston College Earth and Environmental Sciences (Ph.D.Geosciences, UMass Amherst), and Mr. Bruce Porter, (M.S., Physics, Stony Brook)
Description. The purpose of this 5-hour field trip is to observe excellent examples of topographic landforms developed during the last phases of the Pleistocene glaciation, including a drumlin and an esker as well as features developed within the Sudbury River Valley and lowlands associated with the last Ice Age, specifically Glacial Lake Sudbury.
Start: Weston Observatory, Weston, MA. Depart at 9:00 AM.
Stop 1: Drumlin at Drumlin Farms, Lincoln, MA (25 minutes)
Stop 2: Esker at 50 Alpine Rd., Wayland, adjacent to Schoolhouse Pond (25 minutes)
Stop 3: View across an expanse of Glacial Lake Sudbury, at Great Meadows National Wildlife Refuge (20 minutes)
Stop 4—Break at Dunkin
Donuts, 1641 Sudbury Rd., Concord, MA (30 minutes)
Stop 5: Glacial Erratic, Gray Reservation, Sudbury, MA (10 minutes)
Stop 6: In woods adjacent to Curtis Middle School: Kettle Hole; Kame Terrace (~20 minutes)
Finish: Weston Observatory, Weston, MA around 2:00 PM
Meeting Time and Place. 9:00 a.m. at Weston Observatory Parking Lot, 381 Concord Rd., Weston, MA 02493. Saturday, October 1, 2016. Trip begins and ends here.
Take I-95/Rte. 128 North or South (toward Waltham/Weston) to Exit 26, U.S. Rte. 20 West.
Follow Rte. 20 West into Weston. Just after passing Crescent St. (on your right), bear right onto Boston Post Road. This takes you into Weston Center. Pass through the center and turn right onto Concord Road. Follow Concord Road through two forks. Bear left at the fork with Merriam Road, then bear right at the fork with Sudbury Road. Just after the Sudbury Road fork, turn right into the entrance of the Observatory at 381 Concord Road.
Other Logistics. We will have two Boston College Department of Earth and Environmental Sciences’ vans to transport a total of 19 people for this trip in the Weston Observatory parking lot. We will leave promptly at 9:00 AM and will return by 2:00 PM. Breaks/Food: Bathroom facilities are available in Weston Observatory at the start and end of our trip. We will be provide bottles of water in each van; we will have a stop at the Dunkin Donuts on 1641 Sudbury Rd., Concord as a designated break stop midway through the trip. Additionally, there are single port-o-potties at stops 3 and 6. Physical Demands: Stops 1 and especially 2 will involve walking up and down fairly steep hills. Boots are recommended, as is insect spray as we will be in and around meadows and forested areas throughout the trip. Other stops involve walking on trails over easy to moderately rough terrain.
Start: Weston Observatory: Introductions, Acknowledgements, and Glacial Geologic Overview
Stop 1: Drumlin at Drumlin Farms
Drumlins are streamlined molded glacial forms and can either have a core of bedrock or sand and gravel overlain by glacial till (unsorted boulder clay more or less deposited directly by the glacier) or be completely made of till. Usually, their blunt, steeper slope points up-ice, which in this case is correct. Their shape is close to that of an overturned teaspoon.
A drumlin is a low, smoothly rounded, elongated and oval hill, mound, or ridge of compact glacial till, built under the margin of the ice and shaped by its flow (AGI Glossary, 1974). Drumlins are often found in swarms or groups. Where the conditions to form one drumlin exist they often exist over a large area.
Stop 2: Esker
An esker is a long, low, narrow, sinuous, steep-sided ridge or mound composed of irregularly stratified sand and gravel that was deposited by a subglacial or englacial meltwater stream flowing between ice walls or in an ice tunnel of a continuously retreating glacier, and was left behind when the ice melted. It may be branching and is often discontinuous, and its course is usually at a high angle to the edge of the glacier. Eskers range in length from less than a kilometer to more than 160 km and in height from 3 to 30m. (AGI Glossary, 1974)
Stop 3: Glacial Lake Sudbury area:
(a) A glacial lake is a lake that derives much or all of its water from the melting of glacier ice, as one fed by meltwater, or one lying entirely on glacier ice and due to differential melting.
(b) a lake occupying a basin produced by glacial deposition, as one held in by a morainal dam.
Stop 4: Glacial Erratic
A rock fragment carried by glacier ice or floating ice, and deposited when the ice melted at some distance from the outcrop where the fragment was derived. * a relatively large rock fragment lithologically different from the bedrock on which it lies. (AGI Glossary,, 1974)
Stop 5: Kettle Hole
A kettle is a steep-sided, usually basin- or bowl-shaped hole or depression without surface drainage in glacial-drift deposits (especially outwash and kame), often containing a lake or swamp, and believed to have formed by the melting of a large, detached block of stagnant ice (left behind by a retreating glacier) that had been wholly or partly buried in the glacial drift. (AGI Glossary, 1974)
Stop 6: Kame Terraces
A kame terrace is a terrace-like ridge consisting of stratified sand and gravel deposited by a meltwater stream between a melting glacier or a stagnant ice lobe and a higher valley wall or lateral moraine, and left standing after the disappearance of the ice; a filling of a fosse. A kame terrace terminates a short distance downstream from the terminal moraine; it is commonly pitted with kettles and has an irregular ice-contact slope.
Fosse— a long, narrow depression or trough-like hollow between the edge of a retreating glacier and the containing wall of its valley, or between the front of a moraine and its outwash plain. It may result from local acceleration of melting due to absorbed or reflected heat from the valley sides. (AGI Glossary, 1974)
Today’s field trip will take us to 6 glacial features that are outstanding examples of the impact of the glacier that covered New England. We would like to thank all the cooperating agencies who gave us permission to visit their land and who otherwise made this field trip possible. These organizations have as their mission the preservation of land for all of us to enjoy. We owe our thanks to:
Sudbury Valley Trustees – Gray & Schoolhouse Pond Reservations
Great Meadow National Wildlife Refuge
Town of Sudbury Conservation Department
National Audubon Society at Drumlin Farm
Town of Sudbury Water District
Boston College Department of Earth and Environmental Sciences
Professor Alan Kafka: Director of Weston Observatory
Mrs. Marilyn Bibeau: Administrator of Weston Observatory
Mr. Darryl Ribao, Facilities Services, Weston Observatory
Mrs. Stacy Moulis, Professional Researcher, Weston Observatory
http://www.geography-site.co.uk/pages/physical/glaciers/images/drum.jpg accessed 11/18/16
The following are materials prepared by Dr. Kenneth G. Galli for our inaugural Fr. Jim Skehan Geologic Field Trip. You can use these as long as you give proper attribution and as long as you do not include them in materials that are to be sold.
Figure above from “Roadside Geology of Massachusetts,” 2001, by Father James W. Skehan, Mountain Press Publishing Company, Missoula, Montana. Thanks Father Jim!
The two Quadrangles in the upper right corner are the location of our field trip.
The Concord Quad is to the east and the Maynard Quad is west of Concord Quad.
The two figures below come from the Glacial Chapter in: Editors: Noel P. James and Robert W. Dalrymple, 2010:
The Geological Association of Canada’s Facies Models 4 is the essential volume on sedimentary succession interpretation. Presented in full color, this updated edition of the original, highly popular textbook Facies Models incorporates the enormous advances in our understanding of depositional environments since the last edition was issued in 1992. Coverage of this topic is at the advanced undergraduate- to graduate-student level, making this book accessible to anyone with an interest in sedimentary environments.
Published: January 20, 2010 ISBN Number: 9781897095508 Pages: 575 plus index
Facies Models is a classic up-to-date treatment of most major sedimentary depositional environments.
The above photographs were taken by my first college Professor of Geology! Professor Emeritus, William A. Newman, Northeastern University, Boston, MA. He is a Glacial Geologist and a wonderful teacher. Thanks Bill!
On the left is till at Fourth Hill, Scituate, and the other is outwash sand and gravel.
Cross-section C shows the most likely arrangement for the spillway and ice associated
with glacial Lake Sudbury.
The two Figures above from “Roadside Geology of Massachusetts,” 2001, by Father James W. Skehan, Mountain Press Publishing Company, Missoula, Montana.
Figure above from “Roadside Geology of Massachusetts,” 2001, by Father James W. Skehan, Mountain Press Publishing Company, Missoula, Montana.
Dr. Ken Galli at Louis Agassiz's grave at Mount Auburn Cemetary, Watertown, MA.
Bruce Porter (on left, blue fleece and hat) and Dr. Ken Galli (on right at rear of van in BC coat and green hat) — Overivew of main features of
surficial geology of the greater Sudbury area (Maynard and Concord Quadrangles).
Walking up the drumlin at Drumlin Farms! (Stop 1).
Happy field-trippers on top of the esker (Stop 2).
More happy field-trippers on the esker (Stop 2).
Bruce Porter goes over aspects of the esker (Stop 2).
Ken Galli (glasses and green fleece) in center of our field trip group as we answer questions about the formation of eskers and that it is made of
outwash sediments, aka stratified drift, mostly sand and gravel, is a steep-sided, sinuous ridge. (Stop 2).
View of water of swamp/wetland adjacent to esker at Stop 2.
View across wetland along trail.
Ken sets the stage and tells the geologic history of the formation of glacial Lake Sudbury and then later glacial Lake Concord, as well as formation
of Walden Pond. (Stop 3: Great Meadows National Wildlife Refuge). Prior to walking to look at the Sudbury River and to the north to the former
position of glacial Lake Sudbury.
Stop 3 Introduciton: Center map is after Carl Koteff and shows position of glacial Lake Sudbury to south (outlined in blue) and glacial Lake
Concord to the north of area (outlined in red).
Looking ~North at the Sudbury River. Stop 3: glacial Lake Sudbury.
Canoeist enjoys Sudbury River. Does he realize that a glacier "ran through it" in the past?!
Gray Reservation, Sudbury, MA. One of Bruce Porter's signs of his "Glacial Features Walk" self guided tour at Gray. (Stops 4, 5, and 6).
Stop 4: Glacial Erratic at Gray Reservation, Sudbury, MA.
Bruce Porter (red sweatshirt and clipboard) explains aspects of glacial features at Gray Reservation.
Stop 6: Along one of the kame terraces of Stop 6, Gray Reservation. Bruce Porter (red sweatshirt) and Dr. Ken Galli (green fleece). Note the steep
slope down to the right. Our group saw one of the kame terraces. At the base of the slope to the right is a wetland and then another relatively steep
slope rises marking the second kame terrace. These features are more easily seen from near the base of the slope and along a trail that continues
beyond where our field trip ended. In fact, one can park at the Stop 4 location and walk all the way though Gray Reservation and up to this point
if you have the time.