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Deerfield Basalt

A cache by amgleason Send Message to Owner Message this owner
Hidden : 11/13/2007
1 out of 5
1 out of 5

Size: Size:   not chosen (not chosen)

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Geocache Description:

This site is located along the north side of the road on Rte. 2 west. There is a large designated parking lot on the southern side of route 2. You will need to cross Rte. 2 to complete the cache, so be careful crossing the road. This is basalt rock.

To get to this site drive west on Massachusetts Rte. 2 until you reach the vicinity of Turners Falls. You will come upon a fairly large curve in the road. Right on this curve you will see a rather large parking lot on the south side of the road. You will know if you are in the correct parking lot because you can see Turners Falls Dam off in the distance towards the southeast.
Once you are at the parking lot look north across the road. You will see a large rock structure. The color of this rock is a gray to black. The rock is set back approximately 10 feet from the side of the road, so be careful while you observe the rock and complete the task assigned at the site.
What kind or rock are you observing when you look at this rock? Well, you are looking at igneous extrusive rock. When it comes to igneous rock there are two types: igneous intrusive and igneous extrusive. First, what does igneous mean? Well the word igneous comes from Latin, which means born of fire. Igneous rock begins forming beneath the Earth’s surface where the environment is hot enough to keep rock in a molten magma form. This molten magma eventually hardens into rock in two different ways. The first is the molten magma rises, as any hot material will, towards the surface of the earth. As it rises it can reach a shallower depth than which it came from, yet it may not rise to the surface. Here in this new environment the rock will cool, still under ground. This kind or rock is called igneous plutonic. The word plutonic means under ground. This is how igneous intrusive rock is formed. Igneous extrusive, the kind or rock that you are observing, forms a bit differently. This rock also began forming beneath Earth’s surface in the form of molten magma. The difference here is that this molten magma oozes out of fissures, cracks, in rock at the surface of the Earth, or it flows out of volcanoes. Volcanoes in Hawaii flow out lava in this manner. As the rock reaches the Earth’s surface it spreads out and loses the name magma, but gains the name lava. As this rock flows across the surface of the Earth it cools rapidly, much faster than igneous intrusive rock. The entire ocean floor of the Earth was formed this way and it too is igneous extrusive rock. You can imagine how quickly lava cools under water. (DiSpazio, et al. 1996).
Take a close look at the rock. One way to determine that you are observing igneous extrusive rock is that you will see that there are nearly no large grains in this rock. That is you don’t see large mineral crystals. Remember that like ingredients in chocolate chip cookies, minerals make up all the rocks found on the Earth. The rock you are observing does have minerals in it, but it doesn’t have large crystals of them. This is because the rock cooled too quickly. Remember that the rock cooled on the surface of the Earth. Rock that cools on the surface of the Earth had little time to cool, it cools very rapidly. This leaves little time for large grains of crystals to form. For example, if you were looking at igneous intrusive, such as granite, you would see large crystals of quartz, feldspar, and mica minerals. You don’t see this in the rock you are observing. Granite has large minerals because it cooled under ground near the surface but not on the surface of the Earth. The rock you are observing is igneous extrusive called basalt. Some of the rock looks like it has a course texture, but don’t confuse that with large grains of minerals. One can find large grains of minerals in smooth textured rock which may in fact not be igneous extrusive rock. (DiSpazio, et al. 1996)
Where did this large rock structure form? It is possible that that this rock structure formed when basalt oozed from a fissure in rock at the surface of the Earth. It is believed that this crosscut through the road on Route 2 is Deerfield basalt. It belongs to a huge outflow of lava called the Deerfield Basin from the Jurassic period that formed a huge flow of 180 feet thick of basalt that is sandwiched between coarse to fine grained sediment strata. Turners falls is believed to be on one side of glacial Lake Hitchcock this may explain at least one of the sedimentary layers. (Skehan, 2001) In some locations along this rock structure (the eastern and western ends of the structure) you can clearly see vesicular looking basalt. This vesicular rock (looks like tiny holes and tunnels through rock) is associated with hot, gaseous lava flowing out of fissures and volcanoes. This is one more sign that you are observing igneous extrusive rock.
To get credit for finding this earth cache you will need to do the following:
• Find telephone poles numbered 41 and 42. Pace the distance between each pole: count each step. This will give you a good estimate of how long this rock structure is. How many paces did it take you to walk between each pole?
• Look for vesicles (tiny air pockets or air tunnels) on the rock. Give a cardinal direction as to where on the rock you found these air pockets. Using a compass here would be helpful.
• Take a picture of your GPS with the basalt in the background.
• Email your findings with picture.
Finally, if you have the time, check out the rock formations on the south side of Route 2. This rock is sandstone. It’s a sedimentary rock. If you break open a few you may find some fish fossils in the rock. Use caution here as there are signs stating that the dam could release water any time. The Cache is the basalt on the northern side of route 2. This southern side is an add on if you have interest and time.

Visiting this cache site accomplishes several Massachusetts’ required teaching standards in Science and Technology.

Massachusetts Frameworks:

• Give examples of how the surface of the earth changes due to slow processes such as erosion and weathering, and rapid processes such as landslides, volcanic eruptions, and earthquakes.
• Describe and give examples of ways in which the earth’s surface is built up and torn down by natural processes, including deposition of sediments, rock formation, erosion, and weathering.
• Explain and give examples of how physical evidence, such as fossils and surface features of glaciation, supports theories that the earth has evolved over geologic time.
• Use technology such as GPS.
• Describe how the movement of the earth’s crustal plates causes both slow changes in the earth’s surface (e.g., formation of mountains and ocean basins) and rapid ones (e.g., volcanic eruptions and earthquakes).
• Understand how the rock cycle works on Earth.

Inquiry Skills:

• Observe the world from a scientific perspective.
• Articulate and explain the major concepts being investigated.
• Identify and use navigation features of a browser
• Using a browser, “bookmark” a Web site for future reference
• Using e-mail create and send a message
(2007). “Pre-K through Grade 12 Curriculum Frameworks”: Massachusetts’ Department of Education. Retrieved September – December 2007: (visit link)
DiSpazio, Michael, Linner-Luebe, Marilyn, lisowski, Marylin, Skoog, Gerald, and Sparks, Bobbie. (1996) Science Insights: Exploring Earth and Space. New York, NY: Addison-Wesley Publishing Company.
Skehan, James. (2001) Roadside Geology of Massachusetts. Missoula, Montana: Mountain Press Publishing Company.

Additional Hints (No hints available.)

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