Grand Marais's West Bay Glacier Formation EarthCache
Grand Marais's West Bay Glacier Formation
-
Difficulty:
-
-
Terrain:
-
Size: 
(not chosen)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
Lake Superior is the world’s largest freshwater lake by surface area… 3 quadrillion gallons of water! The lake is so large that it significantly modifies the local climate. On average the surrounding air is 5 to 20 degrees F warmer in winter and 5 to 20 degrees F cooler in summer. The surface water temperature of the lake averages about 40 degrees F.
About two million years ago, glaciers advanced into the region. During the Wisconsin glaciation 10,000 years ago, the ice began to recede, ice covered the region at a thickness of 1.25 miles. During this period, a large amount of the basalt and sandstone, which erode much more easily than granite does, was removed by the glaciers. This formed the rough, rugged shoreline on the North Shore today. As the glaciers retreated, they took with them eroded igneous material, much of which covers the rocky beaches on the North Shore. Michigan is the bottom of the basin which filled with the residue from the eroded sandstone and thus the sandy beaches today. Without the immense weight of the ice, the land rebounded, and a drainage outlet formed at Sault Ste. Marie.
Rocks and sediments are added to glaciers through various processes. Glaciers erode the terrain principally through two methods: abrasion and plucking.
As the glacier flows over the bedrock's fractured surface, it softens and lifts blocks of rock that are brought into the ice. This process is known as plucking, and it is produced when subglacial water penetrates the fractures and the subsequent freezing expansion separates them from the bedrock. When the ice expands, it acts as a lever that loosens the rock by lifting it. This way, sediments of all sizes become part of the glacier's load. The rocks frozen into the bottom of the ice then act like grit in sandpaper.
Abrasion 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. This pulverized rock is called rock flour. The flour is formed by rock grains of a size between 0.002 and 0.00625 mm. Sometimes the amount of rock flour produced is so high that currents of meltwaters acquire a grayish color. These processes of erosion lead to steeper valley walls and mountain slopes in alpine settings, which can cause avalanches and rock slides. These further add material to the glacier.
Grand Marais's West Bay is just 1 of many bays formed by glaciers.
Requirements:
E-mail us with your answers. Please don't put your answers in your log.
#1--- Tell us what monument can be found at the coordinates?
#2---Do you think the bay was formed by Plucking or Abrasion and why?
#3--- Observe the land formations of the surrounding areas and describe them.
#4--- Optional: A picture of your GPS with the bay in the back ground, or you may be in the picture if you prefer.
Each Cacher that logs a find is required to submit answers to the questions above (failure to comply will result in a deletion of your log). Per Earthcache guidelines, each cacher is to learn from their visit/experience. That means each cacher must perform the necessary task(s) or requirements to log the cache and earn your smiley.
Any logs that do not meet the above posted requirements will be deleted at the discretion of the cache owner. All logging requirements must be completed within 48 hours of logging the cache online or your log will be deleted unless you have prior permission from the cache owner.
Additional Hints
(No hints available.)
Treasures
You'll collect a digital Treasure from one of these collections when you find and log this geocache:
Loading Treasures