Which way did it travel? EarthCache
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As you are driving down the highway looking at the forest and edge of the road as you travel. Have you ever wondered why it looks the way that it does? This EarthCache looks at the evidence that is used by scientists to determine how the glaciers in the past have shaped the land around us.
The most recent glacial episode in New Brunswick began about 25,000 years ago, when the Laurentide ice sheet overspread New England and Eastern Canada. During its peak development, this ice sheet was centered over eastern Canada and flowed east to southeast across New Brunswick. It became several thousand feet thick, while its massive weight shaped the land as it traveled. Climatic warming forced the Laurentide ice sheet to start receding as early as 21,000 years ago. This melting of the ice sheet left a great deal of evidence behind. The last remnants of glacial ice probably were gone from Maine by 10,000 years ago.
This EarthCache will show you how geologist can look at the land to understand the past. It will give you a new perspective of the land. It will explain a ten-mile trip along the Trans Canada Highway in west central New Brunswick. To best understand this EarthCache you must travel the highway in both directions over this section but need to only travel west bound to complete the cache. The description is going east then returning west because in this section of the road that is the direction that the glacier traveled. As you travel south from Woodstock, east on the Trans Canada Highway, the land is gently rolling composed of relatively soft rock. But as you drive several miles east of Canterbury the land suddenly rises very quickly. This is the edge of the Pokiok Batholith, a very hard course grained granite that was formed during the Early Devonian period deep underground. The rock is easily identified due to the very large grain of the granite. This formation is not a very large one so it will show the movement of the glacier very well. Up until this point in your trip there have been few large rocks and the land has been rolling. But as the glacier moved up and over the harder rock sections of the rock sections near the surface were torn from the bedrock. These sections were broken and tumbled by the glacier as they moved along. As you continue the trip toward Nackawic you will see a great number of these broken sections called erratics all along the road. As you return you will look at them as their number and size changes over the distance you travel.
Boulders that differ from the bedrock beneath are call erratics. He word erratic comes from the old French “erratique” which is derived from the Latin “errare” meaning "to wander." An erratic is a piece of rock that has been eroded and transported by a glacier to a different area; it is left behind when the ice melts, simply dropped in place. Glacial erratics give us information about the direction of ice movement and distances of transport. Glacial erratics can be any size from small pebbles to large boulders the size of a house. This area is a classical example of the type of boulders that were carried here by the glacier and dropped when it melted.
Most glacial erratics appear worn and rounded, and sometimes include beveled or faceted surfaces. During the course of their journey, the rocks were jostled against other erratics or scraped against the underlying bedrock, rounding off corners and planing smooth surfaces, eventually producing their characteristic appearance. Glacial transport also caused some boulders to fracture, producing fresh angular edges.
The composition of glacial erratics can often lead to identification of their point of origin and thereby provide some specific information about the direction of ice movement. At times, a string of erratics of similar composition can be observed across a broad region. These are referred to as "boulder trains," and are defined as a series of erratics that have come from the same bedrock source, usually with some special characteristic that makes it easy to recognize their common origin. Boulder trains appear as long lines or fans of erratics extending outward from their source in the direction of ice flow. Erratics from a given area are nearly always more numerous near their source and diminish in number with distance from the source.
At the posted coordinates you will find a road cut that shows a great deal of evidence about the direction the glacier traveled. The top of this outcrop of rock is what is called a Glacial Pavement. This is a rock surface that has been scraped by glaciers moving over it. Rock fragments frozen into the base of the ice scratched the underlying rock. These scratches are called striations if they are small and grooves if they are large. Scientists use these features to show the direction of ice movement.
To log this EarthCache: Send an email to me through my profile with the following information: At the road cut, describe how the appearance of the rocks can be used as an indicator of the direction the glacier traveled, and give that direction. If possible post a photo of you, your GPS and your group at the glacial pavement, near one of the erratics or near the road cut. It also would be nice if you would post a photo so others would know what they have to look forward to at this earth cache.
Please begin your email with the name of the EarthCache and make sure your log includes the number of people in your group and answer the question.
Traveling West on the Trans Canada Highway
(DO NOT STOP ON THE TRANS CANDA HIGHWAY)
Waypoint #1 (N45 56.081 W67 11.501): This is the first large grouping of erratics that you will see along this section of the road.
Waypoint #2 (N45 57.141 W67 20.598): You will begin to see the erratics scattered all along the side of the Trans Canada Highway.
Waypoint #3 (N45 56.976 W67 19.367): This is the bridge over the Shogomoc River, in this area there are a large number and perhaps the greatest concentration of erratics.
Waypoint #4 (N45 57.249 W67 20.764): This is the exit 223 to Charlie Lake that you will use to find the location of the EarthCache. In a short distance you will find a turn-a-round where the EarthCache site is located.
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