ADK Geology Tour #1 - Hudson River EarthCache
ADK Geology Tour #1 - Hudson River
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A beautiful spot in North Creek to sit and enjoy the river and possible learn something new at the same time.
ADK Geology Tour #1 – Hudson River
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 Hudson River in the North Creek area.
Some background on the Adirondack’s:
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 that continuously fills with 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 the 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”.
Finally, 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.
In addition to the many active mountain building events, the Adirondacks, and the entire Northeast among other areas, saw many significant glaciations. Over thousands of years glaciers (large, moving ice sheets) would move through the area and then retreat again. Each time a glacier moved through it would scrape off anything in its path. As it scraped off soils and less resistant rock, it also gouged surfaces and widened valleys. The material would be carried along with the glacier and deposited in different areas. Each subsequent glacier advance would erode or erase the evidence left from the last one. Long Island is a terminal moraine (end point) of a glacier. A glacier dropped massive amounts of sediment there as it began to retreat from the area and Long Island was formed.
So, WHY North Creek?
First of all, it’s a beautiful spot. So, sit back and enjoy the peace for a minute.
Some of what we discussed above is shown here. One is the continuous faulting and folding that occurred during the many mountain building events. The Hudson follows many of the fault lines on the area and continues along the boundary of the resistant gneiss (pronounced “nice” - a type of hard metamorphic rock) on the less resistant marble. Also, the glaciers that came through the area widened the valley and rounded and scoured rocks as they cut through. They also dropped glacial erratics (a piece of rock that is not similar in size or type to the area where it was found). All of these are present at the Hudson.
The IP will bring you to the north end of a parking pull over on Route 28. After you park walk down along the river side of the parking area and you will see some signs. To receive credit for this cache you must get information from these signs and answer the following THREE (3) questions:
1) When did the last glacier retreat this area?
2) What 2 actions contributed to the rounded appearance of the river rocks?
3) What is the overall orientation of the regions rock fractures?
Email the answers to the questions prior to logging and then, with your log, post a picture of you with your GPS and the river in the background (FACING upstream, or to the north). We understand that these questions could be researched without visiting the site therefore your picture is required – pictureless logs will be deleted.
Take some time to enjoy where you are – you can find garnets on the shore, skip rocks, fish, sunbathe, search for crayfish or just sit on the rocks and take in the view.
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
(No hints available.)