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The Coriolis Effect in Action at the Stamp Sands

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Hidden : 4/18/2013
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The Stamp Sands at Gay – The Coriolis Effect in Action

Cache Summary:   The Stamp sands are located to the south and east of Gay, MI and then South and West along the Lake Superior coast for about 4 miles covering about half of the coastline of the Great Traverse Bay on the Keweenaw Peninsula. The stamp sands stop at the pier that protects the outlet of the Traverse River where Pier Road stops. Visitors will observe how humans and nature have conspired to considerably change this landscape.
Note: "The Gay Stamp Sands are owned and operated by the Keweenaw Road Commission, who have given permission for the use of their land for your EarthCaching enjoyment.  For your safety, Road Commission officials ask that visitors do not enter the area when active mining is taking place."

Figure 1. A satellite photo of the northern part of the Great Traverse Bay showing the gray colored beach areas covered in Stamp sands. Retrieved 7/27/12. Source: Google Earth
EarthCache Lesson:
How have humans changed the landscape and how is nature reworking it?
The main features that visitors will observe are the massed amounts of Stamp sands that were placed in Lake Superior, using water from the Tobacco River to transport a slurry of stamp sand and water via the sluices.
Longshore drift has moved the sands from the vicinity of Gay, MI along the coast. A great amount of the sands lie hidden underneath the surface of the lake. The Keweenaw County Road Commission owns 68 acres here, about 30 million tons or more, along 6,000 feet of shoreline, although there is estimated to be about 500 million tons of Stamp sand in the Keweenaw peninsula as a whole. The sands at Gay, MI are estimated to be least 30 ft thick on average.
Stamp sand is an artificial sand (made by humans) left over from the processing of copper ore (that is rock that contains enough copper in it that it was economically worth processing it, to extract the metal). In the Keweenaw Peninsula, the area of Gay and the Grand Traverse Bay is just one of the places where these black or dark grey sands were deposited in or on the edge of water. In the Stamp sands at Gay, MI. there is still about 0.03 percent of copper plus arsenic and other heavy metals in these sands, that preclude the growth of most vegetation. These may be hazardous and at this time are threatening a reef in the area that is a spawning ground for trout.
The Coriolis Effect causes large bodies of water and air to be deflected, due to the rotation of the earth. In Lake Superior at the Grand Travers Bay this causes currents to move along the coast in a particular direction. This is the main reason for the longshore drift in this direction. Wind will also cause longshore drift, if it is coming at an angle to the beach.
Stop 1 – this is where you should start! Drive from Gay, MI along Gay Park Road in a southwesterly direction. Set your GPS for N 47° 13.521 and W 88° 09.691. At this point you should be able to pull over to the side, stop your car and see through the thin screen of trees to the east, to the grey stamp sands and Lake Superior. This is a good place to begin your journey to the lake shore, between some rather large ponds. The sands are firm to a little soft. Make sure that you are able to clearly see the slope of the sands down to the lake, as there are some high cliffs that should be to the north east of your position. These are near the lake shore! The picture below is approximately at the same navigation point.

Logging Question 1

Measure the distance to the beach using your GPS or by counting the number of normal steps (each of about 3 ft, or 2 ft, if the sand is soft) it takes you to reach the Lake shore. If on average the sands are about 30ft deep and 4 miles long (1 mile = 5,280ft). How much Stamp sand by volume is visible on the beach, in cubic feet?

Stop 2 – N 47° 13.460 W 88° 09.514 Longshore Drift
You should now be at the water's edge. This is where you should take your plastic scooper and scoop up some sand. Throw the sand into the waves and watch which way the sand is moved by the wave coming in and then the return wave. Do this at least 3 times to check that your evidence is the same each time. This will give you the direction of Longshore Drift, that must be either up the coast towards the Tobacco River or down the coast towards the Traverse River Pier.

Logging Question 2

In which direction is Longshore Drift moving the Stamp sands that have been dumped into the Lake by Gay, MI?

Figure 2. Photo taken at Stop 2, showing Stamp sand cliffs and the water's edge, on 7/14/12. Source: M.C.Wardell

Stop 3 – N 47° 13.364 W 88° 09.593 Alluvial Fan
You have arrived at the Cliffs that are being worn away by storms (otherwise the lake water does not reach that far). The Cliffs are collapsing in a very natural way and making mini alluvial fans (Alluvial fans are fan-shaped deposits of water-transported material (alluvium). They typically form at the base of topographic features like the cliffs, where there is a marked break in slope like a notch at the top of the cliff that allows water to find its way more easily down the face of the cliff).
There are 3 basic ways in which these cliffs are being eroded away.
1.      During storms the waves reach further up the beach and wear away the cliff from the bottom, undercutting the cliff, so that the top of the cliff leans out over the bottom of the cliff face (the top of the cliff juts out further than the bottom of the cliff).
2.      It rains and small temporary streamlets carry water and Stamp sand sediment from the top of the cliff to the bottom of the cliff, where the water slows down and deposits much of its sediment. Mini Alluvial Fans form at the bottom of the cliff. When this happens the bottom of the cliff sticks out further than the top of the cliff.
3.      On dry and windy days the breeze picks up and carries small particles of sediment away from the cliff or loosens the sediment, which then falls further down the cliff face. The top of the cliff will erode faster than the bottom, as it is more exposed to the wind.

Logging Question 3

a.      Are the top of the cliffs closer to the water's edge than the bottom of the cliffs?
b.     Which of the 3 types of erosion from the explanation above, do you think is the main one at work here?
c.      Explain why you think the erosion is happening according to your answer to the 'b' question above?
d.     What do you think is causing the mini alluvial fans to form?
Figure 3. Photo taken at Stop 3, on 7/14/11, showing the height of the Stamp sand cliffs and a small alluvial fan. The person in the picture is approximately 6 feet tall. Source: M.C. Wardell

If you are interested you can go and have a look at the other end of these Stamp sands at Big Traverse River Pier. Look at either side of the Pier and ask yourself why the Army Corp of Engineers built this pier?


Stamp sands – material produced as waste from mining for metals such as copper. The rock (ore) is smashed by a mechanical stamp, the metal falls to the bottom and the waste rock is usually gravel to sand sized.
Arsenic – a poisonous metal, that at one time was used to kill rats.
Copper ore – rock that contains enough copper that it is economically worthwhile to mine and process it for its metal.
Longshore Drift – the movement of sand and other small rock particles along a beach in a particular direction, often due to the prevailing wind direction or prevailing offshore current.
Sluice – an artificial channel for conducting water, often fitted with a gate (sluice gate) at the upper end for regulating the flow. (
Slurry – a thin mixture of an insoluble substance, such as cement, clay, or coal, with a liquid, such as water or oil. (
Mid-Ocean Ridge – A place on the ocean floor, that extends for hundreds or thousands of miles, where lava is pushing through to the surface and pushes the ocean further apart. The lava cools and creates new rock, which is itself pushed away by newer lava and the process continues.
Alluvial fan – a fan-shaped deposit formed by running water (and the affects of gravity), where its velocity is abruptly decreased, as at the mouth of a ravine or at the foot of a mountain or cliff.

Earth Science Literacy Principles Big Ideas
What's the Big Idea? The Earth is constantly changing!
When you look down on the Earth from space, there are not many structures built by humans that can be seen. The Great Wall of China is one of them. However the human species is changing the planet, sometimes on purpose, but more often than not by accident and without thinking of the consequences. The Stamp sands at Gay, MI cannot be seen from outer space, but they can be seen by aerial photography. Also a great deal of the sands that were moved here by miners are not seen, but are just off of the Lake coast under the surface of the water! Have you noticed that almost nothing grows on this sand? Grass grows on sand dunes that are not covered in water every day. This does not happen on the Stamp sands. Why is this? The Stamp sands contain copper and arsenic and other trace heavy metals. They are poisonous.
There has been talk of using these Stamp sands to make roof tiles, which do not allow moss to grow on them. We use millions of roof tiles every year in the U.S., it is possible that these poisonous sands could become a useful resource at some time in the future. If this happens they will be scooped up and the sands will disappear over time, to be replaced by the natural sands on which they currently lie!

Common Earth Science Misconceptions:  
Misconception 1 – the Coriolis Effect is demonstrated every time you flush your toilet.
Despite what you may have been told or shown by a teacher or other adult, the Coriolis Effect is too weak, to cause the spin of water to be clockwise or anticlockwise, when you flush your toilet or pull the plug on your sink full of water.
When you flush a toilet, the vortex of water will spin either way depending on how the water enters the bowl. You can test this by filling a sink full of water and using your hand, swirl the water clockwise, then pull the plug (observe the spin direction) and try it again by swirling the water anticlockwise the second time that you try this.
Misconception 2 – the Earth used to change, but now it basically stays the same.
Well after you have experienced this EarthCache, you should be able to see that both humans and nature are continuously changing the way that the Earth is and looks. Just because you cannot see the hour hand on a clock move by staring at it, does not mean that it does not go round the dial at least once every 12 hours. Many of the processes that the Earth experiences on a daily basis are slow and steady (it is like watching grass grow) but that does not mean that they do not happen. Seeing is believing- right!? Do your fingernails grow? Are you sure? Can you see it happening if you watch your fingernails? Of course not! Yet the Atlantic Ocean is moving apart (getting wider every year) at the Mid-Ocean Ridge at about the same speed with which your fingernails grow (2-3 centimeters a year)!

The owner of this cache is a participant in the Michigan Teaching Excellence Program (MITEP) through Michigan Technological University, which teams with science teachers to improve science teaching and learning.

This work was supported by the National Science Foundation award # 0831948

Dictionary. (n.d.). Retrieved July 27, 2011 from

Stamp sands. (n.d.). Retrieved July 27, 2011 from
[A satellite photo of the northern part of the Great Traverse Bay showing the gray colored beach areas covered in Stamp sands]. Retrieved 7/27/11 from: Google Earth

Gagnon, John (2010, August 18th) Alumnus Teams with Tech to Reclaim Stamp Sand and Grow an Industry. Retrieved from

[Map of part of the Keweenaw Peninsula, showing the Grand Traverse Bay and Gay, MI]. Retrieved July 27, 2011 from
Miller, Marli Bryant. (n.d.). Retrieved July 27, 2011 from

Schaetzl, Randall J., Darden, Joe T., and Brandt, Danita S. Michigan Geography and Geology. New York: Pearson Custom Publishing; 1 edition (January 8, 2009).

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