The above pictures have been graciously given by fellow Geocacher Klepper! Hope you enjoy them as much as we did! Its amazing to see what the Rock looked like 60 years ago. Amazing how something as simple as a giant rock can influence your life.
When you arrive at ground zero, you will be shocked in what you find. Like in the Wizard of Oz when Dorothy's house land in the middle of Oz on the Wicked Witch of the East, the boulder you are now looking at has no rightly business being there. We call this an “Erratic Boulder”, which means that it came from somewhere else. We know it is erratic because there is no source near ground zero that this boulder could have come from. So how did such a large boulder find its way to the Saskatchewan prairies? The only reasonable explanation is that a glacier moved this monsterous piece of rock.
The last glacier that moved across the province was called the Laurentide ice sheet. This ice sheet reached its maximum size some 18,000 years before present (BP) when it covered most of Canada. At that time, a thick layer of glacial ice a kilometre in depth covered most of Saskatchewan. After 18,000 years BP the Laurentide Ice sheet gradually retreated northeastward, present only in the far northeast corner of Saskatchewan around 8,000 years BP, with the last vestige of ice likely gone by 6,000 years BP. As the ice sheet advanced, it eroded and transported rocky materials Southward like the erratic boulder sitting at ground zero. As such, it is believed that this erratic boulder in particular was moved from the Craiton/Flin Flon area of the Canadian Shield, approximately 620 km, to its current resting spot
Glacial Geology
Rocks and sediments are added to glaciers through various processes, but glaciers erode the terrain primarily through two methods: abrasion and plucking.
As the glacier flows over the surface of the exposed bedrock, it lifts blocks of rock that are swept into the ice. This process is known as plucking. Through this method, sediments of all sizes become part of the glacier's load. Depending on the location of the said boulders, either on the top of bottom of the glacier, the rocks could act act like sandpaper as they are dragged across the ground.
The action is the second type of errosion called Abrasion. And again, this occurs when the ice and the load of rock fragments slide over the bedrock and function as sandpaper that smooths and polishes the surface situated below. In turn, the transported boulder will also have signs of abrasion in the form of smooth or polished edges. One Visible characteristic of glacial abrasion is glacial striations, which are produced when the glacier's base ice contains large chunks of rock that create scratches in the bedrock. By mapping the direction of these scratches, or "flutes", researchers can determine the direction of the glacier's movement.
In general, material that becomes incorporated in a glacier are typically deposited in two distinct types:
Glacial till: Till includes a mixture of undifferentiated material ranging from clay size to boulders. These deposits are stratified through various processes, such as boulders' being separated from finer particles.
Glacial Erratic: These are the larger pieces of rock which are encrusted in till or deposited on the surface. They may range in size from pebbles to boulders, but as they may be moved great distances. They may are often made of drastically different types of material upon which they are found.
What is a Glacial Erratic?
A glacial erratic is a piece of rock that differs from the size and type of rock native to the area in which it rests. "Erratics" are carried by glacial ice, often over distances hundreds to thousands of kilometres. Erratics can range in size from pebbles to large boulders weighing hundreds of tons. The term "erratic" is commonly used to refer to erratic blocks, or in other words, large masses of rock, that have been transported by glacier-ice. These "erratics" have often been lodged in a prominent position in the glacier valleys or have been scattered over hills and plains.
Erratics were once considered evidence of a vast flood 10,000 years ago. Ancient legends of an epic flood come from many cultures including Mesoamerican, Sumerian, Hebrew, Indian culture. In the 19th century, many scientists came to favour erratics as evidence for the end of the last glacial ice age 10,000 years ago, rather than just a great flood. Other than plucking, some geologists have suggested that landslides or rockfalls initially dropped the rocks on top of glacial ice, which caused the glacier to transport the rocks when they kept moving. When the ice melted, the erratics were left in their present locations.
This cache can be a bit tricky to find. There is a turn off approximately 17 km North of Watrous on the Number 2 Highway. It's an old grid road that will take you directly to ground zero. Take the utmost caution on this road as it can be quite terrible. I made it the first time in my little Accent, but a 4x4 would be ideal. Pleasse do not attempt this road during winter. To register this find, you need to answer the following questions. Do not post your answers with your log . . . please email them to me directly:
1. Are there any signs of abrasion on the sides of the erratic boulder? What does this tell you about the location of the boulder when it was moved by the glacier?
2. Moraines, accumulation of glacial debris or till, are commonly found in Glacial Regions, but in the areas surrounding the Erratic Boulder, these landforms are not visible. Why not?
3. What is speeding up the rate of errosion to this paticular Erratic Boulder? How does the boulder differ from the above pictures from 1954?
4. Please take a picture of the Erratic Boulder and post it with your log. It would be awesome if you were in the picture, but that is not necessary. (Completely Optional)
Please note that this is an Earthcache, which means there is not a physical cache at ground zero. For more information on Earch caches, please visit www.geocaching.com or www.earthcache.org. Also a big shout out to Geocacher Klepper who first brought me to this site to find his cache GC15J28 Glacial Rock.
Sources:
http://en.wikipedia.org/wiki/Glacial_erratic
http://esask.uregina.ca/entry/glaciation.html