ADK Geology Tour #3 - Lake Durant Roadcut
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A fantastic road cut near Lake Durant.
NOTE: Remember, although located near a rest area and along the bike trail, this is a main route - please be aware of the road conditions during winter and keep it safe. CANNOT be done safely or easily with plowed snow along the road edge.
ADK Geology Tour #3 – Lake Durant Road Cut
The northeastern United States, New York in particular, is filled with some amazing and highly varied Geology. The Adirondack Mountains are an example of some of New York’s rich geologic history and they are one of the most beautiful places in the state. We are putting together the Adirondack (ADK) Geology Tour as a series of Earthcaches that will take you to some fascinating and beautiful places in the region. There are hundreds of locations in the Adirondacks that would be great for locating Earthcaches however we won’t be placing Earthcaches at all of them. This one is the Lake Durant area between Blue Mountain Lake and Indian Lake.
Although the roadside pullover is available 24/7 it is recommended to the do the cache during daylight hours only due to the proximity to the road and the difficulty you would have distinguishing features within the rock outcrop at night.
Some background on the Adirondack’s:
The IP will bring you to a pull off along RT 28 across from Lake Durant. Before we begin, if you are looking for an easy pull over, read some signs, jot down some info and drive off Earthcache – this one isn’t it. This Earthcache will make you read, interpret, and search the rocks, hence the higher difficulty rating. It’s a beautiful spot with some amazing rocks. That being said - this is NOT a drive by cache - if you are not comfortable getting out and walking in the bike path along the side of the road - do not do or try to log the cache. The idea is to get close and learn about the rocks, NOT drive by, snap a shot and earn a smiley - that wouldn't be fair to those who complete it correctly.
The Adirondack mountains are commonly referred to as “ new mountains from old rocks”. This nickname comes from the fact that the rocks that are exposed in the highlands of the Adirondack mountains are much older than the process that formed the mountains themselves. The majority of the rocks that make up the Adirondack region are some of the oldest rocks on Earth, OVER one billion years old. Approximately 600 million years ago the continent developed a rift (a tear in the earth’s crust that continuously erupts magma and pushes the two sides apart) and began splitting apart, each side moving in the opposite direction of the other. As this occurred the area between the two masses filled with sediments and volcanic deposits (from the magma at the rift zone). Over time sea level rose and much of New York was covered by this ancient sea.
Then the rifting ended. The ancient sea began to close and our continent collided with the island arc that had developed during the rifting process. This event is called the Taconic Orogeny (or mountain building event). During this event the sedimentary deposits that made up the shorelines were scraped off and thrust onto the continent as the rest of the mass was forced deep into the earth. Over the next millions of years mountains were built and eroded, and shallow inland seas advanced and retreated.
While this was occurring, the rocks that had been forced so far below the surface of the continental crust were subjected to intense temperatures and pressure that altered their chemical make-up, known as “metamorphism”. At these intense pressures and temperatures the rock becomes “rock taffy” and gets stretched and twisted into folds. Materials that are similar in makeup begin to band together and once cooled, form wonderful pink and green gneisses (pronounced “nice” - a type of hard metamorphic rock) with pronounced layering and banding. In other instances, the rocks cool and undergo another folding event and the entire unit of rocks is folded again. Much like layering several colors of play dough and then bending them up into an “S” shape; you can still see the different colors of the play dough, but they are all folded together.
In some instances, the variations in the resistance of materials to deformation is also evident. For example, in this road cut (and commonly throughout the area) the gneisses are cut by a large band of white marble that is uneven and chaotic in appearance and is often referred to as “marble stew”. The term “marble stew” is owed to the plastic (taffy like) nature of the marble as it flowed and plucked the more resistant, less plastic and brittle pieces of gneiss off the surrounding area and dragged it along with the mass resulting in a stew-like mixture.
Another feature that helps demonstrate the viscous nature of the rocks is a xenolith. A xenolith is a piece of a rock that is trapped within another rock. Typically, the xenolith was torn off of the neighboring rock during an intrusive event. In other words, as a rock taffy was pushing its way into another rock formation, it ripped pieces off of the formation and dragged it with it. Once cooled, these xenoliths show up as a piece rock that doesn’t match the rock matrix that it is within.
Then, about 5 million years ago an igneous intrusion of anorthosite began pushing up the center of the metamorphosed sediments and began forming a dome. Picture a large piece of play dough that is rolled out flat. Now take a bouncy ball and place it under the play dough and slowly begin to push the ball up. You would notice a dome forming with play dough on top and the bouncy ball hidden beneath.
The same occurred in the Adirondacks, the metamorphosed rocks would be the play dough and the igneous anorthosite would be the bouncy ball. Over time erosion by wind, water and glaciers eroded the less resistant metamorphic rocks to reveal the harder, more resistant igneous core that makes up much of the High Peaks. Amazingly, the Adirondacks are still rising today at a rate of 2 -3 millimeters per year.
. Now, for the fun part!! From the pull over at the IP (N 43° 50.720 W 074° 24.370) walk a short distance south along the SAME side of the road. To receive credit for this cache you must use the information above to locate and photograph (close up so we know it’s the right spot, with your GPS in each photo for scale) the following:
1) a Xenolith rock
2) a section of Gneiss illustrating strong layering and banding
3) a portion of the “marble stew”
After taking the photos - upload them to the cache page and label them as to which photo is which.
This Earthcache is meant to make you think and develop a better understanding for the power of nature that you are witnessing when you look at rocks, especially rocks in the Adirondacks. This isn’t a test and we won’t delete your smiley if your answers and photos are incorrect – we are really looking for you to show that you read the material and actually tried to find the corresponding area.
Most of all – HAVE FUN!! Although we read through everyone's answers on all of our EC's we are not able to respond to each one individually. We hope you enjoy this Earthcache and maybe even learn something new about the world around us.
Additional Hints
(Decrypt)
whfg rznvy hf vs lbh unir nal dhrfgvbaf - ab arrq gb rire gnxr n QAS ba bhe pnpurf, jr'yy tynqyl uryc bhg.