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Location A: Kame

Location B&C: Kettle

Location D: Erratic

Location E: Kame

Great Meadows Reservation: River and Kame

The Woods Behind Lincoln-Sudbury Regional High School










Location A

Location A is a kame, a conical hill formed by uneven heating on the top of the glacier. For more information on how kames form, see our Geologic Features page. This hill formed during the retreat of the Laurentide Ice Sheet approximately 15,000 years ago. For more information on the Laurentide Ice Sheet see our Background page (Richardson, Raymo and Raymo).







Locations B&C



Locations B and C are kettle holes.  Kettle holes are depressions in the ground caused by ice breaking off the glacier onto the ground as it is retreating.  This block of ice then gets covered by sediments that get dumped on it by the glacier.  As the ice melts, a depression is left behind, which sometimes fills with water, forming a kettle pond (Richardson).




(Image drawn by Alex Gough)



Location D

Location D is an erratic, a rock that has been dropped by a glacier.  It had previously been plucked up by the glacier, and as the glacier melted, it was dropped onto the soft sediment it now sits on.  For more information on plucking, visit the erosion section of our Background page (Richardson).
This rock can be easily identified as an erratic because it is a large rock sitting on a pile of soft sediment, so it must have been deposited by something, as it could not have broken off any parent bedrock, as there is none around. For more information on erratics, visit our Geological Features page.
    This specific erratic is a large granite boulder.  There are several types of weathering occurring on this rock, some chemical, and others mechanical. For more information on weathering, visit the Background page. Specifically, this rock is experiencing frost wedging, as made evident by the cracks running over the surface.

    The cracks in the rock allow water to get in, freeze and then expand.  Because water expands as it freezes, the rock is slowly prised apart (Richardson, Tarbuck and Lutgens).

    This erratic is also experiencing weathering by way of organic acids(top of photo below).

    The lichen and moss on the rock excrete acids which dissolve certain minerals in the rock which they can use as food. This changes the composition of the outside of the rock, often resulting in a colour change (Richardson, Tarbuck and Lutgens).
    Some level of oxidation is also happening on the rock.  The colour change shown in the picture shows that some minerals in the rock must be metallic and reacting with the oxygen in the air.
    While we cannot really see it, it is probable that the granite is experiencing hydrolysis because of its content of feldspar. Granite is comprised of three minerals, quartz, feldspar and biotite mica. Feldspar, when it reacts with water creates kaolinite, a type of clay (Richardson).
    This rock was deposited here about 15,000 years ago, as the Laurentide Ice Sheet retreated from the area (Raymo and Raymo).



Location E
Location E is also a kame, a conical hill comprised of sediments deposited by the glacier during its retreat (Richardson).  For more information on how kames form, see our Geological Features page.

The Hill at the corner of Lincoln and Concord Road
    The hill at the intersection of Concord and Lincoln Roads (located on the left of the image below) is also a kame, a hill created by unstratified sediments being deposited in a conical shape (Richardson). For more on how kames form, see our Geological Features page.


Great Meadows Conservation Area

    The main hill of this area is part of a kame delta, a triangular depositional feature formed at the snout of a glacier (Allaby). For more on how these form see our Geological Features page. This hill is probably made of stratified (well sorted) sediments.  Because kame deltas are associated with meltwater they tend to be made of a single size of sediment, as liquid water sorts the sediments out by size before dropping them (Richardson, Hansen).
    On the top of this hill there is a depression near circle 4, similar to the ones in the woods behind L-S locations B&C.  This depression is also a kettle hole, formed when a piece of ice broke off the glacier and was buried in sediments.  For more on how kettles form, visit our Geological Features page.


    The Sudbury River is a fairly old river, as can be identified by the great amounts of meanders that it has.  Additionally, it has features such as meander cutoffs and oxbow lakes, which indicate that the river has moved around quite a lot, meaning it is a fairly old river (Richardson).  For more on river features visit our Geological Features page.