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Urban Geology Lesson

A cache by roadwanderer Send Message to Owner Message this owner
Hidden : 9/18/2012
1 out of 5
1 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:

This is an Earthcache, it does not have a container but rather highlights a site with geologic features. The coordinates bring you to a location where you will see two natural building materials, two rocks that are very different in their origin, composition, appearance and usage. To claim this cache you must send answers to the questions to the cache owner, you don't need to get 100% so don't worry!

The parish grounds are open to the public during daylight hours. There is a labyrinth in the rear for meditation and relaxation. The graveyard is hallow ground and should be treated as such. If you would like a history of the church and/or a self-guided tour of the graveyard contact me and I will email you a copy.

Rev. William Horton made a donation to build St. Anna's Chapel (1862-1863) in memory of his only child Anna Maria who died at an early age. The chapel was build in the High Gothic Style, very unusual for Federalist Newburyport at that time. The architect Rufus Sargent chose granite for the structure and slate for the roof. Why were these two materials chosen?

Rockport Granite Gray Slate

Photos courtesy of R. Weller-Cochise College

GRANITE is an igneous rock whose name is derived from the Latin word "granum" meaning granular. Igneous rocks were formed when magma, a semi-liquid deep under the surface of the earth, went through a process of cooling and crystallization. These rocks that slowly cooled and hardened within the earth are called intrusive and granite is classified as an Intrusive Igneous rock. The minerals contained within these rocks (the grains or crystals) had an opportunity to separate and enlarge creating the granular appearance of granite. Because we find these rocks on the earth's surface we know that they were lifted as rocks that covered them were stripped away by weathering and erosion over millions of years .

Granite is one of the most common and abundant rocks on earth, it is composed of several mineral grains or small crystals that are all approximately the same size and can be seen with the naked eye. Colors, however, vary from light to dark grays, yellow, green and white depending on the actual minerals within the granite and where the rocks were excavated.

St. Anna's Chapel is made from Rockport Granite which is noted for its big speckles and hard nature resulting from intense pressure to the rock below the surface of the earth. The Laurentian ice sheet eroded the sedimentary rock that covered the granite about 15,000 years ago and brought the granite close to the surface all around Cape Ann in MA. Rockport Granite (hence Rockport, MA) is usually gray black and white speckled but can also be shades of green, yellow and brown. This would have been the reason this stone was chosen for the chapel it would withstand the test of time, look beautiful and be fire-proof. Rockport Granite was also readily available just down the road where numerous quarries were in operation on Cape Ann. In 1922 the old church burned down and the existing church and parish house were built out of Rockport Granite to match St. Anna's Chapel.

The Custom House Maritime Museum in Boston is said to be the tallest building in the country without a steel frame, it is built of Rockport Granite which attests to its strength and durability. Other structures built from this granite include the base of the Statue of Liberty, the supports of the Brooklyn Bridge, cobblestones on Nantucket Island, the locks on the Panama Canal and six monuments in Central Park in NYC.

SLATE is a metamorphic rock which means a rock of any kind (igneous, sedimentary or metamorphic) that has undergone physical or chemical change because of heat or pressure or both. Slate began as shale (sedimentary) that formed from clay and silt deposited at the bottom of ancient seas 450-600 million years ago. Mountain building forces subsequently folded and compressed the shale while intense heat and pressure changed the clays into new minerals like mica, chlorite and quartz completing the transformation into slate. These new mineral grains are so tiny the surface of the stone looks uniform not granular like granite. The resulting stone has a unique parallel alignment of minerals that allows the stone to be separated (split) into layers - a distinct characteristic of slate referred to as cleavage. If you look at rock cuts through a highway you can see evidence of the crushing and lifting to the earth's crust, it may look like the rock is in layers similar to the pages of a book, this is metamorphic rock.

Most slate is found in the eastern US near the VT/NY border or in PA and in the Alps in Europe, areas near the roots of old folded mountains where millions of years of motion and erosion took place. Slate is resistant to weathering, is fire-proof, is insulating, can be cut into sizes and shapes, comes in a variety of colors and was readily available in the Northeast during the 1800's. Purple, green, black, red, gray and variegated slates were common and popular colors from the VT/NY region. As early as the 1300's the Welsh used slate for roofing and as they immigrated to the US they brought their skills and experience with them. In 1839 the first slate quarry began operation in VT.

Slate was used for early gravestones and was used for the headstone of President John F. Kennedy's grave. In the 1800's people would use chalk to write on a small piece of slate framed in wood like an early IPod and it was found on all schoolroom walls (blackboards) before whiteboards and markers were invented. Slate roofs are common in the Northeastern US, however, schools, churches, hospitals and government buildings across the country have slate roofs. The expense of shipping and construction made it impractical for the common household to use slate. With the introduction of mass produced asphalt shingles the use of slate for roofing declined in the early 1900's but slate is still used in the finest pool tables and has gained popularity in countertops and flooring in more recent times.

To claim this EarthCache please e-mail me the name of the cache and the answers to the following questions but DO NOT include answers in your log:

  1. From the sidewalk on the West estimate the height and length of one of the foundation slabs of granite on the chapel.
  2. What colors make up the slate roof of the chapel and what colors are the slate roofs on the church and parish hall?
  3. Why do you think these roof colors are so different?
  4. Describe any difference between the granite of the chapel and the granite of the other two buildings.
  5. What do you think caused this difference even though it is all Rockport Granite?
  6. Do you see any other uses of slate or granite on this property from the cache coordinates, if so what is it?
  7. Optional: Post a picture of your favorite feature from one of the buildings.
CONGRATULATIONS to Froedo and the "clan" and Haverood for their FTF!

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223 Logged Visits

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Coordinates are in the WGS84 datum

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