Washington Creek Seiche EarthCache

Washington Creek Campground in Windigo is one of our favorite places to camp in Isle Royale National Park.  The campground is located right alongside Washington Creek, which has an interesting characteristic of flowing upstream about as readily as it flows downstream.  This earthcache is about observing and understanding that phenomenon.

A seiche (pronounced SAYSH) is an oscillating wave that travels through an enclosed or partially enclosed body of water. The term was promoted by the Swiss hydrologist François-Alphonse Forel in 1890, who was the first to make scientific observations of the effect in Lake Geneva, Switzerland. The word itself comes from a Swiss-French dialect, and means “to sway back and forth”.

Seiches can occur in any enclosed or partially enclosed body of water (basin), such as a lake, harbor, bay, swimming pool, bathtub, or even a coffee cup. Although they can be caused by seismic activity or even tsunamis, they are typically caused when strong winds or atmospheric pressure changes push water from one side of the basin to the opposite side. The water continues to “pile up” there until the wind subsides or the pressure changes, and the gravitational pull to restore equilibrium releases it and causes it to roll back to the other side of the basin. Once there, it is reflected back and begins oscillating back and forth across the basin. Such oscillation can continue for hours or days while gradually subsiding. (Note that it is not necessary for the basin to be entirely enclosed, but only enough to cause the reflection). The frequency of oscillation within a body of water is determined by its size, depth, and contours, and by the temperature of the water. The magnitude of seiches can vary greatly, from being virtually imperceptible to depths of 10 feet or more.

There are many online resources describing and documenting seiches, including the following which contributed to the above information:

• https://en.wikipedia.org/wiki/Seiche
• http://oceanservice.noaa.gov/facts/seiche.html
• http://geo.msu.edu/extra/geogmich/seiches.htm
• http://www.air-worldwide.com/Blog/Say,-What-Is-a-Seiche-/

To earn a “find” for this earthcache, send an email to the owner with the following information (don’t disclose any of it in your log). You may make your observations at the posted coordinates, or at any other point in the campground where you have access to Washington Creek. (Note that loons often nest in Washington Creek early in the season, and while they are nesting you will need to take care to work within the instructions and guidelines provided by the park staff).

1. What geographical features of Washington Harbor are favorable for the creation of seiches? Consider such things as its shape, compass orientation, the direction of the prevailing winds, the size of Lake Superior compared to the size of the harbor, etc.
2. Explain how seiches in Washington Harbor relate to the upstream/downstream flow of Washington Creek. Consider the effect of the size of the harbor compared to the size of the mouth of the creek, etc.
3. Observe the upstream/downstream flow of Washington Creek and report the following:
   1. What is the period of the upstream/downstream flow cycle you observe? To answer this question, determine the length of time from one distinct point in the cycle (for example the point where downstream flow ceases and turns upstream) to that same point in the next full cycle. (This can take several minutes, so don’t be in a hurry). Do not rely on the apparent motion of the surface of the water or of small items floating on it, as that may be affected by the wind; instead observe the direction that the vegetation growing along the bottom of the creek is being pulled by the current. Feel free to include pictures of the same vegetation when being pulled upstream and downstream.
   2. What is the change in the depth of the water through a full cycle? Hold a stick of some kind vertically in the water and observe the distance between the high and low water marks on the stick.
   3. Please indicate whether you made your observations at the posted coordinates or at some other location. If at some other location, please indicate which campsite it was nearest to.

In your log, please indicate how long your trip to Isle Royale was, briefly describe your itinerary, and describe some of the highlights of your time on the island. Feel free to include some of your favorite pictures of your trip.

Isle Royale is the least visited, but the most re-visited of the National Parks.  Access to the island is only by boat or float-plane from Grand Portage or Grand Marais, Minnesota, and Houghton or Copper Harbor, Michigan.  Plan and prepare for your trip before coming here.  Here are some websites with some helpful information:

• http://nps.gov/isro
• https://nps.gov/isro/planyourvisit/index.htm
• https://nps.gov/isro/planyourvisit/transportation-services.htm
• http://irkpa.org