Basalt Towers EarthCache
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This is hike is a fair challenge: know your physical limitations. You will hike a total of 2.5 miles over rocky and steep terrain climbing about 700ft to a point called Deadtop. Do not attempt the hike in bad weather unless you’re an experienced hiker.
To get to this site drive south on U.S. route 5 from the Holyoke-Easthampton line for about 1.6 miles to Reservation Road. Turn right onto Reservation Road. Follow Reservation Road until you get to the gate for the reservation where you will pay $2.00 to park. Continue along Reservation Road past Lake Bray, on your left, to a very small rotary where you will find a Visitor’s Center for the park and parking.
While at the park remember Earthcache’s mantra, “Leave no trace behind.” Abide by all park rules and hours. This is a hike, so remember besides your GPS you should carry a day pack with all the necessities required for hiking along small mountain terrain. A cell phone is a good idea in case of an emergency. CAUTION: don’t hike this trail in poor visibility as there is some very steep terrain along ridge and trail. If you take children with you keep them away from the edge of the cliffs, and if necessary hold onto their hands.
The best route to the cache site is to walk back along Reservation Road, in the reverse direction that you drove to the Visitor’s Center, to the intersection of the Metacomet-Monadnock (M-M) trail. Turn right, a southerly direction, onto the M-M trail. Continue along this trail tracking your distance and location on your GPS. You will hike approximately 1.2 miles to an observation point where you can clearly see the basalt towers. The Latitude and Longitude coordinates given are of the observation point, not the actual basalt towers. CAUTION: The basalt towers stick out from the side of the ridge and there is no reason to approach them or climb on them. Just observe them from the observation location given with the coordinates. These basalt towers will remind you of Devil’s Tower in Wyoming. There is good reason for looking like Devil’s tower, which is explained below. Once you reach this observation point have a seat and observe the towers.
What are these basaltic towers? Well, they are actually referred to as “Columnar Basalt.” They are called this because as one observes them one can clearly see that the rock looks as if it was formed as columns. Basalt is a type of igneous rock. Igneous is Latin for fire, so one can say rock born of fire. Basalt is a hard rock usually gray to black in color. Basalt is an extrusive igneous rock which means that it was rock that flowed out of either a volcano or fissure (a crack on Earth’s surface) as lava and cooled and hardened on the surface. Igneous extrusive rock cools and hardens quicker than igneous intrusive, which is rock that cools and hardens below Earth’s surface. An example of igneous intrusive is granite. These basalt towers are “Mafic,” which means that they are rich with iron and magnesium. (visit link)
Basalt is said to be fine-grained because it cools so quickly that there is little time for crystals of any sort to form. In fact as you hike the M-M trail and begin to get close to the observation site look at the basalt along the trail and look at the rocks closely. You will see small holes known as vesicles. They were formed by bubbles of gas that were trapped in the upper part of a lava flow. (Brady and White, 1990)
Now that the type of rock that makes up the towers is clear, how did these towers form? Well the columnar shape of these towers suggests that the towers are actually basaltic, volcanic plugs. Volcanic plugs are also called volcanic neck or lava neck. These are all synonyms for landforms created when lava hardens within a vent of a volcano that was once active. Plugs are usually preserved when the volcano dies and weathering and erosion remove surrounding rock that is less resistant. Remember that this volcanism occurred some 200 million years ago. Since that time there has been much weathering and erosion that occurred in the Connecticut Valley. Remember that the last ice age ended approximately 15,000 years ago. That’s a great deal of time and exposure to the forces of erosion. Over time the less resistant rock and soil has been eroded away leaving behind the harder basaltic rock of Mt. Tom. In the end the plug remains and is a signature of previous volcanism. (visit link) Supporting the theory of these towers being volcanic plugs comes from an article written by Richard M. Foose, James J. Rytuba, and Michael F. Sheridan. They wrote “Volcanic Plugs in the Connecticut Valley Triassic near Mount Tom, Massachusetts” in the Geological Society of America (GSA) Bulletin; November 1968; v.79; no.11; p. 1655-1661. In this article they state that a number of basaltic volcanic plugs are well exposed on the east flank of the Mt. Tom Range near Holyoke, Mass. The basaltic towers you are observing are on the west flank, yet still appear to be basaltic plugs.
James Skehan, the author of Roadside Geology of Massachusetts, writes that basaltic magma flowed out of rift faults in the Connecticut Valley about 200 million years ago. He states that that “Two flows of Holyoke basalt-a 320 foot think flow and a 255 foot thick flow- form a north-trending mountain ridge from Hartford, CT to Easthampton Township, where it turns east. The ridge includes the rugged profiles of Provin Mountain, East Mountain, and Mount Tom.” He writes that if one views Mt. Tom from Northampton, Massachusetts one can see huge basalt flows on the west side of Mt. Tom. He says that, “Basalt cracked into great columns at right angles to the layering of the lavas. The fractures shape the steep cliff face on the west side of the range.” Skehan’s findings seem to suggest that the basalt flowed from large fissures rather than volcanoes. Fissures with lava flowing out of them are still caused by volcanic activity, so whether the basalt towers were once a volcano or just part of huge lava flows that cracked into columns may still be debatable.
The main point is that you can directly observe a site in Massachusetts that has a volcanic history.
To get credit for finding this earth cache you will need to do the following:
• Determine the straight line distance to the towers from the observation point (this is an estimate).
• Determine a magnetic azimuth from the observation point to the center of the basalt towers (don’t forget to bring your compass).
• Look off to your left as you face the basalt towers. You will see a track and field, what is the magnetic azimuth to the center of the field?
• Estimate the height of the basalt tower furthest from the ridge.
• Take a picture of your GPS with the basalt towers in the background.
• Email your findings with picture.
• Stay awhile and enjoy the view of the Connecticut Valley below, it’s spectacular. Mt. Tom Reservation is a great place to spend a day outdoors.
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).
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
Resources:
(2007). “Pre-K through Grade 12 Curriculum Frameworks”: Massachusetts’ Department of Education. Retrieved September – December 2007: (visit link)
(2007). “Volcanic Plug”:Wikipedia, the Free Encyclopedia. Retrieved October 25, 2007: (visit link)
Brady, John and White, Brian. (1990) Fifty Hikes in Massachusetts: Hikes and walks from the Top of the Berkshires to the Tip of Cape Cod. Woodstock, Vermont: Backcountry Publications.
Foose, Richard M., Rytuba, James J., and Sheridan, Michael F. (1968, November) “Volcanic Plugs in the Connecticut Valley Triassic near Mount Tom, Massachusetts.” GSA Bulletin; v. 79; no. 11; p. 1655-1661.
Skehan, James. (2001) Roadside Geology of Massachusetts. Missoula, Montana: Mountain Press Publishing Company.
Additional Hints
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