This EarthCache will take you to a beautiful natural area right along the main walking trail in Marti Park, New Wilmington, PA. There is a bench to sit and admire the view, especially in the spring with the native wild flowers and in the fall for the colorful foliage. But first, lets learn a little bit about how this gorge was formed.
EROSION & Gorge Formation
The process in which most gorges are formed is called erosion. Erosion occurs when a natural force wears down rock and earth. The most common natural forces that cause erosion that form gorges are water, glacial retreat, and geolocial uplift.
Water Erosion
Water Erosion is mainly in the form of streams, rivers, or creeks. The flow of the water gradually cuts through layers of hard rock to form a deeper channel than existed before. This is not a fast process, generally taking hundreds to thousands of years to deepen its channel and erode the bedrock. The eroded sediment is then carried downstream. Over time, erosion will take place and form the steep walls of the gorge, which you are witnessing now where you are standing or sitting. Flooding of the stream or creek will increase the pace of erosion in that area.
Glacial Retreat
Another key contributor to the formation of gorges is the Glacial retreat or advance. Glacial Movement cuts deep grooves into the earth's crust, forming gorges with steep walls in the bedrock. As the glaciers would then either melt, or retreat after an ice age, the deeply cut bedrock and gorge walls would be exposed. Streams, creeks, and rivers often flow in the channel that is on the floor of the gorge after the glacial recession.
Glaciers once covered most of the northern hemisphere, including western Pennsylvania, with the last ice age ending about 10,000 years ago.
Geological Uplift
Geologic uplift also forms gorges. Geologic uplift is the upward movement of the Earths surface. Geologic uplift is often associated with earthquakes and orogeny, the process of creating mountains. During geologic uplift, rock layers beneath the Earths surface bump against the surface layers. Softer layers of surface rock erode.
Erosion and geologic uplift often work together to create gorges. Parts of streams or rivers can be elevated, along with land, during the process of geologic uplift. As rivers or streams flow across this uplifted surface, waterfalls form. Over time, the power of the waterfall erodes the softer rock layers underneath, causing the original river bed to collapse and create a gorge.
FUN FACTS: The word gorge is derived from the same word in French, meaning throat or neck.
A gorge is in the same family as a canyon, however; not nearly as big!
IN ORDER TO CLAIM THIS AS A FIND, PLEASE OBSERVE THE AREA AND ANSWER THE FOLLOWING QUESTIONS VIA E-MAIL(brc1984@gmail.com).
1. From your observations, which of the factors above were instrumental in the formation of this gorge? Defend your answer.
2. How tall are the gorge walls? You can check this with your GPSr via elevation at the floor and the top.
3. How wide is the body of water that flows through the floor?
RESOURCES USED: http://education.nationalgeographic.com/education/encyclopedia/gorge/?ar_a=1 http://faculty.kutztown.edu/friehauf/Pennsylvania_history/1000_Pennsylvania_tectonic_history.html http://www.ehow.com/how-does_5130993_gorges-formed.html