Framingham is Creepy!

Do you see anything odd about this picture?



The trees on the side of the hill are tilted. This is an example of a process known as "Downhill Creep" or just "Creep."



SOIL CREEP

"Soil Creep is just a slow adjustment of soil and rocks that is so hard to notice unless you can see the effects of the movement. These effects would be things like fenceposts shifted out of alignment, or telephone poles tipping downslope.
Another effect is the way a grass covered slope seems to ooze downhill forming little bulges in the soil. This heaving of the soil occurs in regions subjected to freeze-thaw conditions. The freeze lifts particles of soil and rocks and when there is a thaw, the particles are set back down, but not in the same place as before.

Gravity always causes the rocks and soil to settle just a little farther downslope than where they started from. This is the slow movement that defines creep. Creep can also be seen in areas that experience a constant alternation of wetting and drying periods which work in the same way as the freeze/thaw. Monitoring is essentially done through observation of the effects of creep. Since the process is so slow, it can only be monitored in terms of flow over long periods of time."

http://earthsci.org/processes/geopro/massmov/massmov.html



This hill is a lot bigger and a lot steeper than it looks! The slope is well in excess of 15% in both direction, so it qualifies as a steep hill. According the the Framingham Conservation Committee Master Plan Draft, "The development costs associated with construction on steep slopes are extremely high. Necessary expenses in order to develop these sloped include grading, retaining wall and vegetation in order to reduce run-off, erosion, lateral creep, or frost heaving. Consequently, these areas would be best left as undeveloped open space or conservation land."

Framingham Conservation Committee Master Plan Draft

The side of the hill that faces east has a 15% to 20% slope.


The south face of the hill leads directly to the house, and has a slope that exceeds 25%.

Creep is a normal process that affects every sloped surface. The amount of creep is affected by other factors besides the pitch of the grade. Excessive water, especially if the soil contains a large amount of clay, makes the slippery and more inclined to creep.

EXPANSIVE CLAY SOILS

In some parts of the country they have something called "expansive clay soils". The clay expands when wet and contracts when dry. The expansion/contraction action exacerbates the creep process just as the freeze/thaw cycle described above. Despite the fact that Massachusetts is not affected by expansive clay soil according to the above map, the soil sample I dug up a few weeks ago definitely contracted when it dried.

Vegetation helps to stabilize the soils if present. The roots of plants, shrubs, and trees not only hold the soil in place, they also absorb excess moisture. In general, a slope without vegetation tends to move more than a slope with vegetation. There are exceptions to this rule, however. The weight of trees, plants, and bushes can also make soil heavier and more susceptible to gravity. This is especially true for slippery soils on bedrock.

Clay Soil? Not Here!

I dug a hole in my backyard and found clay.

I didn't know clay soil was even in Massachusetts. But I live on it, and so I know it's here! This is what MY CLAY SOIL looks like today.

It looked exactly the same six months ago when I first dug it up. It's WET. It's MOLDABLE. It's MUDDY. It's DIRTY. But mostly it is WET.

Evidently, clay soils can dry up and become as hard as cement in periods of drought. That can be REALLY BAD for grass and plants and flowers. I don't know if Framingham has ever had such a drought, or if it would affect my yard if it did happen. Given the nature of clay, it will take a long, long time for this saturated soil to dry up at all; never mind turning into cement. It could happen, of course. I just can't imagine it being anything but fully saturated around here. I mean, the trees are mossy!


What is clay soil? Well, clay particles are extremely small, with 1,000 times the surface area in a given volume of soil compared with larger sandy soil particles. As a result, clay packs closely and binds water tightly by surface tension preventing it draining away.

Clay particles, bound end to end and side to side in extensive planes, are stacked in a sandwich like matrix and held together by electrochemical forces. This platelike stacking of horizontally arranged clay particles results in a large surface area. When these horizontal aggregations are stacked high and consolidated over time, they can be quite tight and sticky. Clay can hold a lot of nutrients, and some kinds can hold quite a bit of water, but the structure of clay doesn't let air and water move through it well. Most of the water in a clay soil is so tightly bound to the clay particles that plants can't get it loose.

You can't garden very well in clay soil. All the gardens in this yard have plastic laid down and real good soil laid on on top.
All the good dirt is just about gone, now.

Clay can even act like QUICKSAND in some circumstances! My husband remembers going to the "clay flats" in Braintree, and jumping on the clay like a trampoline. Every ten years or so, someone would break through the clay and start to sink to their death! The firetrucks always rescued the victims in time, fortunately.

But there isn't any clay soil within miles of my neighborhood, according to the USGS Soil Survey:

According to the map legend, clay soil would be BLUE. Do you see any blue north of route 9?

I felt cheated to find clay after researching neighborhood soil, but I wasn't being reasonable. The government doesn't sample every inch of soil, and there are pockets of clay soils everywhere.

I had to contact an expert to find out why there are there are pockets of clay soil everywhere. I was lucky enough to find an expert in Professor Lawrence McKenna from Framingham State College. Professor McKenna didn't mind explaining the topic to someone as clueless as I am.

As I understand it, clay soil is a glacial phenomenon in Massachusetts, like virtually all the topography and geology of our state. In some cases, the retreating glaciers left behind small ponds of water not fed by streams or rivers. Over the centuries, the fine dust and light particles carried by the wind would get drawn to the water and trapped there. Layer upon layer of very small particles accumulated over time, and remained when the water was long gone. These layers of infinitesimally small molecules are now known as clay.

Clay is great for pottery and tiles and pipes, and has thousands of other beneficial uses. But clay soil is always a problem to build on. It is bad for gardening, bad for lawns, and very bad for foundations. Clay soil can crack a foundation right down the middle, or keep a foundation so wet that mold grows inside the walls and spreads everywhere. (It can be potentially dangerous if you jump on it, too!)

But that is not all that clay can do. Wait until you hear about how CREEPY clay soil can be!

Framingham Topography and Glaciers

Hydrology isn't the only factor that determines whether your house and basement is dry. How much SOIL(and the kind of soil)under and around your hose is important. The TOPOGRAPHY of the area (or how many hills are around you and how steep the hills are) is very important, too. Soil and Slope determine whether you are affected by runoff of water; either seasonally or after heavy precipitation.

In Massachusetts, the soil is usually made up of glacial and post glacial deposits over bedrock.

Framingham soil is typically made up of sand and gravel deposits left behind from retreating glaciers.

The glacial history of Framingham is easy to see because of the glacial landforms present in the town. Framingham had a lot of DRUMLINS, for instance.

Drumlins are oval or elongated hills composed of dense till believed to have been formed by the streamlined movement of glacial ice. The most famous drumlins in Massachusetts are Bunker Hill and Beacon Hill. The Harbor Islands in Boston Harbor are drumlins, as well. When I personally imagine a drumlin, I always picture World's End in Hingham, a Trustees of Reservations property where I spend a lot of time as a child. It turns out that World's End is one of the 30 islands of the Boston Harbor Islands National Recreational Area.

Framingham also has Kettle Holes, or Kettle Lakes, which are formed by chunks of ice left behind by glaciers that melt into lakes.

Lake Cochituate is also a kettle lake, as is Walden Pond in Concord, MA.

There are areas in Framingham that are not buildable because they are designated wetlands, or because they are under water, or because the slope of the hills is too steep (>15 degrees.) You also can't build on sites where there isn't enough soil over the bedrock to excavate for sewage systems or septic systems.