Beginning around 15,000 years ago, the continental ice sheet receded from southern Maine, uncovering the northern-most parts of Maine several thousand years later, around 10,000 years ago.
The lower left photo (taken by Karl Kreutz) is what Maine looked like. This is from Greenland, which is the only one of the 6 or 7 continental ice sheets from the northern Hemisphere to have survived to present day.
The ice sheet is constantly moving forward, as can be seen by the broad debris bands and the glacial till being dumped at its base as massive shear planes bring subglacial debris to the margin.
Note the range in grain size in the glacial debris; clay and silt-sized particles up to and beyond boulders. This non-sorted debris is called GLACIAL TILL.
Below the glacial till is a glacial meltwater stream, carrying finer grained material such as clay, silt, sand, and fine gravel.
The person is walking on sand bars that spread across the stream valley. We see these deposits in specific parts of Maine, except there are trees, roads, and homes built on them.
The photo at lower right (taken by Karl Kreutz) shows a strong meltwater stream flowing along the ice sheet margin in Greenland. Note the basal shear planes bringing glacial till to the margin. The meltwater sorts out the till into
clean sands and gravels.
Sand & gravel deposits are important for several reasons, such as providing granular material for roads bases, asphalt mixes, concrete aggregate, and many other construction purposes.
A vital function of these sand & gravel deposits is their ability to store and transmit groundwater in large volumes and at large rates, giving them the name AQUIFERS.
Rainfall and melting snow rapidly infiltrate the soil that lies on the upper 6 feet of these sand & gravel deposits. It becomes groundwater and moves rapidly downhill by the gravitational force,
emerging at the surface once again as a stream, lake, or spring. The water then flows back to the ocean, where it is again evaporated, rises, condenses to form clouds, and falls again as rain or snow, endlessly cylcing through Maine.
Maine has an excess of groundwater, nearly 5 TRILLION GALLONS PER YEAR. Maine could easily supply New York City with clean groundwater supplies (around 400 BILLION GALLONS PER YEAR). The Portland, Maine
water district uses around 9 BILLION GALLONS PER YEAR from Sebago Lake, which could easily supply many times that.
The above left photo shows a typical muncipal water district facility, while the right photo shows a PUMP TEST for a HYDROGEOLOGY investigation of an aquifer.
The above left photo (taken by Karl Kreutz) shows coarse cobbly gravel outwash, while the above right photo (taken by Karl Kreutz) shows medium to coarse sand outwash. This valley, in Kangerlussuaq, Greenland,
is very similar to many valleys in Maine. Many towns draw their water supplies, as well as many thousands of homeowners, from these sand and gravel deposits (aquifers), characterized by rapidly moving groundwater below the surface.
The above left photo shows a SOIL TEST PIT and SUBSURFACE INVESTIGATION. This type of work encompasses both PEDOLOGY (the study of soils) and GEOLOGY (the study of material deeper than about 6 feet).
Detailed data collected from these test pits can yield valuable clues about the type of soil, rock, and glacial environment on a property.
The above right photo shows the internal structure of an ESKER (or horseback), which was once the storm water plumbing system for the 2 mile thick continental ice sheet. Eskers contain, predominantly, very clean and coarse gravels, and
are highly valued for construction material and water supply.