Island’s Erratic – The Islands Provincial Park EarthCache
Island’s Erratic – The Islands Provincial Park
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This earthcache will bring you to a location where you can see evidence of the glacial retreat and what it left behind to give us some idea of its power.
Welcome to Nova Scotia’s first and oldest camping park opened some 50 years ago on land jutting out into Shelburne Harbor. The Islands Provincial Park is located on 350 million year old granite. The position of the park offers an exceptional view of Shelburne town’s marina and historic waterfront. Granite boulders pepper the land, and outcroppings rise three-stories out of the ground. For campers, picnickers, photographers, and natural history and geology buffs, The Islands is a coastal natural history treasure chest open for the explorer.
The story of this earthcache begins with the retreat of the last glacier as climatic warming forced the ice sheet to recede and drop its load of stone. These stones are known as erratics. 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. Boulders that differ from the bedrock beneath or sitting on top are call erratics. The word erratic comes from the old French “erratique” which is derived from the Latin “errare” meaning "to wander." Glacial erratics are important to scientists because they give 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, like this one. This area is a classical example of the type of boulders that were carried here by the glacier and dropped when glacier melted. The small ridge behind these erratic is covers but many smaller boulders. Their placement tells an interesting story not only due to their size but how they were piled as the glacier melted and the power it must have taken to move them. The most recent glacial episode in Nova Scotia 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 Maine into the Maritimes. It became several thousand feet thick and shaped the land as we see it today. Climatic warming forced the Laurentide ice sheet to start receding as early as 21,000 years ago.
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 smoothing surfaces, eventually producing their characteristic appearance. Glacial transport also caused some boulders to fracture, producing fresh angular edges. As you look at these erratic imagine the forces necessary to break something of that size or the size of the ice sheet that must have moved them to this area.
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. In this case if you look carefully at the sides and edges of the erratic you will notice very little wear from movement, which generally indicates that the rock has not traveled a great distance. Geologists identify erratics by studying the rocks surrounding the position of the erratic and the rock of the erratic itself. It is easy to see why erratics were once considered evidence of a biblical flood, but in the 19th Century scientists gradually came to accept that erratics pointed to an ice age in Earth's past. Geologists have also suggested that perhaps landslides or rockfalls initially dropped the rocks on top of glacial ice. The glaciers continued to move, carrying the rocks with it. When the glacier slowed and finally stop it began to melt. This melting slowly and gently dropped the boulders that it was carrying. Occasionally these boulders came to rest precariously perched on other erratics.
To log this Earthcache: You must send an email to me through my profile with the following information: At the posted coordinates describe what you feel was the cause of the splitting of the erratic (or the smaller one close to the rail trail) and how it might have come to rest in that position. When you post your log please include a photo of you or your hand, your GPS and with the erratic in background. Please begin your email with the name of the earthcache and make sure your log includes the number of people in your group. In your log please take the time to describe what you find interesting about this location and the park.
Please remember to help preserve and protect this beautiful park for the enjoyment of future generations. Plants, animals and rocks are an important part of its natural heritage. Please do not damage or remove them and please make sure to practice “Carry-in-carry out" to keep this park special for the future visitors.
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