Natural Bridge State Park is a day use facility, open from Memorial Day through Columbus day each year. Park hours are from 9:00am to 5:00pm, 7 days a week. A fee of $2.00 per vehicle is charged to help defray the cost of maintaining and staffing the park. If you do this EarthCache after 5:00pm or during the winter please place your $2.00 in one of the donation boxes and mention with the fee, that you were there EarthCaching.
During the Cambrian period within the Paleozoic Era around 550 million years ago, the area we now call Natural Bridge State Park began its formation.
During this time this entire area was flat and underwater. Covered by a warm shallow ocean, seashells were deposited here and dissolved into calcium carbonate sediment. Over many millions of years, the sediment began to build up to the point where its own weight compressed it into a soft sedimentary rock known as limestone.
As we move forward in time, the entire planet began its continental drifting away from and towards other continents. During this time the Berkshire Mountains were formed by the continental collisions called orogenies. The very very slow process of building Mountains was caused by the collisions during this time. These collisions and lifted, folded and buckled the earths crust forming the mountains around you. The Taconic Mountain Range and the Hoosac Mountain Range were caused by such continental collisions. These ranges reached heights of 14,000 to 20,000 feet. The crystalline marble found it this area was formed when the limestone was metamorphosed and recrystallized by tremendous pressure and heat during the mountain formation.
The creation of the natural Bridge did not begin until much later in geologic history, after the ancient Taconics had been eroded down and the marble exposed. About 2 million years ago , a mere eye-blink of geologic time, the climate cooled down in the northern hemisphere, allowing continental ice sheets to grow and push southerly across the northern third or so to the United States - including all of new England, which has been buried beneath a mile or or more of ice at times during the Ice Age.
Theses glaciers advanced and melted back several times over the past 2 million years. The most recent retreat began about 13,000 to 15,000 years ago in the Berkshire region.
Natural Bridge itself was created by the billions of gallons of water that ran off across the land as the glaciers retreated, melting back during warm periods, such as present times.
The water that flowed along Glacial Hudson Brook became channeled along weaknesses in the bedrock, vertical fractures called joints. The brook, caring a load of sediment ranging from silt to cobbles, corroded down along the joints, creating the chasm which the Natural Bridge spans. The water was also somewhat acidic, and removed some of the marble by dissolving it. It was this solution process which opened up the joints sufficiently for them to capture the brooks flow. At any rate, we can see this joint control in the right angle turns and the straight runs the brook makes along them as it passes through the chasm and under the Natural Bridge.
The Natural Bridge itself was created where a joint took the stream underground for a stretch, preventing the water from wearing away the bedrock marble of the Bridge.
Studies suggest that the Hudson Brook chasm, and Natural Bridge, were probably created over the course of two or more advances and retreats of the continental ice sheets or there local lobes. It is likely that what we see in the park today had been largely carved out by the time the ice retreated some 13,000 years ago. Water released during the last retreat probably only deepened the chasm by a few feet.
The process continues today on a much smaller scale as the Hudson brook slowly carves out the chasm deeper - perhaps no more then an inch of so every hundred years.
To log this Earth Cache please click on "Message this owner" at the top of the page and answer the following questions.
1) How many steps are on the stairs that will put you about eye level with the top of the Natural Bridge?
2) What is so special about the dam above the beginning of the chasm?
As with all EarthCaches, please do not post any pictures that will give away any of the answers.
During construction, just answer any questions you can.