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Welcome to my geology page! During Summer 2006, I took a course on Geology and Earth processes through the American Museum of Natural History in New York. Below are some of the sites I explored locally in Massachusetts. Most of them are in Framingham, Natick, Southborough, or Marlborough. Afterwards, you will find some sites that Mr. Ward and I explored in preparation for some field work next year.

This first picture was taken when I was searching in Southborough for a "mylonite," which is a kind of metamorphic rock.

This rock outcrop is in Natick and was created by a volcanic mud flow. The ancient volcanoes heated up the glaciers on the surface, causing sudden melting. The flow of water would collect mud and rocks, and it eventually turned into this layer of rocks. After forming rocks, the glaciers eventually passed over them, carving smooth grooves as they went by. The grooves go from left to right in the picture. Thanks to Mr. Ward for showing me this site!

This picture is from a large outcrop of Alaskite by the intersection of Route 9 and Highway 495 in Framingham. You can see a large vein of quartz running up and down in this picture. Supposedly, there are also some veins of magnetite in this rock, but I didn't see them at the time.

Only in New England would there ever be a rock called "puddingstone." It's a kind of conglomerate, meaning that it has all sorts of different kinds of stones and rocks in it. This rock was from Newton, by the intersection of Route 9 and Route 128. It's on the river bank.

This was one of my coolest finds! You can see some of the horizontal layers in this rock and also a huge vertical crack. as you can see, the different sides of the rock must have shifted after the crack, because the layers don't match up on both sides. Look for example at the thick, lighter layer. The left side is shifted downwards, and the right is shifted upwards.

As for the type of rock, I'm not sure, but I found it in Southborough.

This picture and the rest are of a special rock formation I found in Marlborough, near the intersection of Route 20 and Highway 495. The rock formation consists of a gentle slope, and that's me at the top! For more detail, read my posts to my class about the rock below all of the pictures.

The short story is that it's a metamorphic rock formation of many beautiful colors. The green and pink rocks are quartzite from sand on the ocean floor, and the darker layers are volcanic rocks that flowed over the sand when this portion of Massachusetts was a volcanic island chain called "Nashoba." This happened millions of years ago, before Pangaea was even formed.

This is a close-up showing the swirls of metamorphic rock and the beautiful colors.

Notice again the bends in the rock. These layers were originally flat, but when the rocks were buried in the earth, they were under such high pressure and temperature, they deformed a little to form the curves you see here.

Here's a nice shot of the different layers. Remember, the darker layers are the volcanic rock.

This is a pretty interesting part of the rock, which is only a few inches wide. It forms a neat zebra-striped pattern here. This is because there's a quartz vein that runs left to right in this picture. (The quartz is crystallizing from the quartzite). When it was stressed by a lot of pressure, the quartz vein fractured, splitting off perpendicularly and causing the zebra-stripe pattern you see here.

Fieldwork with Mr. Ward

This is Chesterfield Gorge, where a dramatic flow of water cut through the rock here.

Notice the sharp cliffs of metamorphic rock.

Here is a pothole that the river has carved out of the rock.

Notice the texture of the rock on the river bank, where water must have once flown to erode the rock to look like this.

Here's another site we visited, which featured some natural marble. At the top of this picture is a man-made marble dam, and you can see the water begin running through the natural marble below. The water carved out an interesting path through the rock.

Here you can roughly see the marble natural bridge--it looks like an arch in the top center of the picture. The bridge was formed when the river carved out the rock below, leaving a natural bridge above.

The sign on the bridge reads:

"Natural Marble Bridge

You are standing on the only marble bridge in North America. It is 15 feet thick and spans a distance of 30 feet across the chasm. The marble in the bridge was formed when limestone, a rock made of ocean sediments, was subjected to tremendous pressure and high temperatures during mountain building. The heat and pressure transformed the limestone into marble."

And here's a picture of the cliff faces of the old marble quarry.

This is cooled volcanic rock from Mount Tom. Look carefully and you'll see that Mr. Ward is pointing out columns that formed from the unusual way the lava formed here. The picture really doesn't do this cliff face justice--it's really amazing in person. This basalt has formed hexagonal (six-sided) columns.

Maybe you can see the columns better in this picture. I'm standing on a few that are grouped together. the columns are about four inches wide each.

Finally, here is a rock on Mount Tom that has undergone severe weathering. Have you ever seen a stripe of crystals in a rock? Usually, we call that a "vein" of quartz. In this rock, a vein of some hard mineral has eroded more slowly than the rest of the rock, making it look like the rock has ribs. The softer rock eroded away more quickly, but the harder rock was more durable and remained.

Here's another example of a rock with soft and hard layers. The harder layers (top and bottom) have remained while much of the the soft rock layer (middle) has eroded away. Ms. Harrigan's puppy Remy, found some shade when we were at this rock in the Amherst Museum of Natural History's rock garden. Click on the picture for a larger version.

Finally, here's a picture of the 7th grade staff minus myself (someone had to take the picture) at Turner's Falls after a good hunt for dinosaur footprints. Click on the picture for a larger version.

Post #1 about the Marlborough formation

Marlborough, MA--beautiful outcrop of smooth, layered rock

I took a few field trips trying to find a site that really interested or intrigued me, using several roadside geology books. Finally, from "Roadside Geology of Massachusetts" (Skehan, 2001), I found a site just a few miles from my apartment. The site is on Hayes Memorial Drive, just south of Route 20, in Marlborough, MA. The area has a number of storehouses and office buildings, but the site is surrounded by undeveloped forest.

It is a large area of slightly sloping, brightly colored layered rock, approximately 30 feet wide on average, and probably around 150 feet long. The lines of layering run up and down the slope, which runs downwards (towards the west) to the street. The colors in the rock are quite striking and interesting because I've never seen such colors in Massachusetts before. The layers are varied in width, from half a centimeter to 3 or 4 centimeters. To the left and right of this rock are outcrops of single-colored rock, which is more representative of the area.

The book I used mentioned bright pink and green colors, but these tones were in actuality just shades of the brownish-grey rock tone. The colors are still quite vibrant, as you can see in the pictures.

At one point, I found an interesting part of a rock with lines streaking perpendicular to the lines of the layers. This is shown in the picture attached to this post. Most of the layers ran left to right, but there's a distinct zebra-striped pattern running up and down in the picture. Quite unusual, and I have no clue what it means.

The surface of the rocks was quite smooth--possibly from weathering, but I'm guessing that glaciers might also be the culprit--although smooth, I remember some grooves (and I'll take notes on this next time).

My book describes the area as "pink and green metamorphosed cherts." Indeed, the layers have been twisted and turned somewhat, so you can tell immediately that this is metamorphic. (Also, the rock has been turned so that the layers are visible from the top as opposed to the sides). Supposedly, the pink and green rocks are quartzite, which were "clayey cherts on the ocean floor near active volcanoes that periodically spewed basalt lava over the top of the cherts." And the glossary tells me that "chert" just means a sedimentary rock mostly made out of quartzite.

Post #2 about the Marlborough formation

Marlborough, MA Metamorphic Rock

Again, I'm reporting on the same rock as you can see in my week 2 post. From a bedrock geologic map of Marlborough, I see that this outcrop occurs in a region labeled "Marlboro Formation," which includes "thinly layered amphibolite, biotite schist and gneiss, minor calc-silicate granofels and felsic granofels."

This area of Massachusetts was part of a volcanic island chain called the Nashoba terrane. this is a narrow terrane that runs southwest to northeast through eastern MA. Nashoba runs right next to Avalon, which it is very similar to. In the lack of research I've found on Nashoba, let me give you some background on Avalon. Avalon broke off of Gondwana at the end of the Precambrian era, about 550 to 490 million years ago, turning into a volcanic island chain. "Late Precambrian quartzites of eastern Massachusetts may have originaly been deposited as beach sands on the continental shelf of Gondwana" (Skehan, 14).

These two terranes, along with two more that eventually form the eastern part of New England, collided a few times while drifting towards Laurentia (North America). Eventually, Laurentia and all the small terranes collided with Gondwana to form Pangaea around 425-370 million years ago.

The rocks composing the layers of this outcrop include volcanic rocks and sedimentary quartzite. The quartzite is rich with either garnet, which turns it pink, or green epidote, which turns it green. The layers alternate as the sand or clay was deposited on the ocean floor, then covered with lava from the volcanic islands, and so on. Eventually the rock was metamorphosed within the earth and eventually pushed back to the surface. Over time, the surface has weathered to provide the smooth texture. Being on a slope has probably helped with this as water will drain down this rock.

Sources:

Skehan, James W. "Roadside Geology of Massachusetts," Missoula, Montana: Mountain Press Publishing Company, 2001.

Bedrock Geologic Map of the City of Marlborough, Mass., 2002. City of Marlborough GIS.

Raymo, Chet and Raymo, Maureen. "Written in Stone: A Geological History of the Northeastern United States," Hensonville, NY: Black Dome Press Corp., 2001.

Last Updated August 20, 2006.