The Features And Current State Of The Baraga Cliffs Area

The Baraga Cliffs have been under observation ever since the Michigan Department of Transportation (MDOT) rerouted US 41 to create a scenic outlook on top of the cliffs. The cliffs are located seven miles north of Baraga, MI. Over the years the cliffs have had rapid cliff recession, this has lead to concerns to the stability of the cliffs with US 41 not far from the cliff face. Due to the ongoing effects of erosion the Baraga Cliffs’ stability a hazard analysis of the cliffs was conducted to determine the dry and wet intact rock strengths. Allowing for determination in the stability of the Cliffs and the qualities of the Rock formation (Jacobsville sandstone) that makes up the cliff. Fundamentally evaluating the risks and the current mitigation options as acceptable.

In the past MDOT has requested an analyze of the stability of the cliffs, this study was conducted by Vitton and Williams in 2008. Prior to this there has not been a definitive study publish on the Baraga Cliffs, the study concluded that the cliff recession ranged from .15 to 1.5 inches a year, and that there is no indication for large scale collapse being possible. As of 2008 the road was not immediately threatened but the roads stability could start to deteriorate soon. And it was recommended that the road be moved to a farther distance to allow for a stable slope to form. USGS Professional Paper 1693 published in 2004 talks about the erosion of coastal bluffs in the great lakes, specifically how erosion occurs, the paper concludes that the erosion and transport of shoreline sediments by wave is the most significant geomorphic process along the great lakes bluff shores. There are two major ways the wave erosion affects the stability and recession of the bluffs.

First is Bluff toe erosion, which is caused by surface waves generated by winds across the surface of the lake. The waves are cable of both direct and indirect erosion, Kamphuis (1987). The waves breaking on the lower bluff face cause the removal of fallen material at the bluff base, this causes the base of the bluff to be cut into and can lead to large slides. Lake bed downcutting is a second form of erosion that causes the stability to indirectly be altered. Downcutting is the process of coarse sediments and larger particles being dragged across the nearshore zone, causing it to erode and producing deeper than usual waters near the shore, this can cause the waves to be bigger and have more energy to hit the bluffs with. Causing faster and heavier erosional conditions.

The Baraga Cliffs area in question are located approximately 7 miles north of Baraga, MI, With a approximate latitude of 46°52'0.00"N and a longitude of 88°28'40.00"W. The Baraga Cliffs are composed of Jacobsville sandstone which is a light reddish-brown oxidized medium grained quartz sandstone with bleached layers and cross bedding. The Jacobsville tips to the southeast and ends at the south end of the keweenaw. To the North the sandstone thickens rapidly to over 1000m as it goes under superior. The formation dips north from approximately 1 to 5 degrees. The Jacobsville Sandstone formation was apart of the lake superior segment of the mid-continental rift system as it subsided during the Precambrian age. Jacobsville sandstone is exposed at both the east and west ends of the northern part of the upper peninsula. The formation was overlaid by paleozoic sediments which were removed via erosion except for a couple remnants located near the cliffs, for example the “Limestone Mountain” which is actually a dolomite approximately 11 miles west of the cliff.

The area once held features such as stamp mills both to the north and south of the area in question, The stamp mills were built in the early 1900s to process the copper ore mined near, the mills deposited billions of pounds of waste sand that was then pumped into lake superior. Theses stamp sands were then deposited along the shoreline creating beaches. There was once a ore dock that stretched into the water south of the cliffs that trapped a large amount of stamp sands which provided protection from the erosive forces of the water and would have decreased the cliff recession, as the dock ruins became less prominent the stamp sands were washed southward causing numerous problems in addition to the protective beach in front of the cliffs being removed which cause the recession of the cliffs to speed up.

The Current state of the site is approximately a 70% incline with a Talus Slope that reaches about 4 meters above the water line, the beach in front of the cliffs contains large fragments of cliff that have fallen down or been eroded, they have features of being well rounded and angular. There was noticeable bedding, and the overburden on top of the cliff was slumping over with trees at the edge leaning at a noticeable angle. There was a moderate amount of foliage growing on the talus slope and along the side of the cliff. A significant portion of the lower cliff face that was exposed was fractured and cracked, with very little structural integrity at the immediate surface.