Hi
One of the natural phenomena that I see at the cottage on a regular basis is the seiche. It is easily noticed at our location because the bay is shallow, with a very gentle gradient to deeper water; a change of a few inches in water depth can cover or uncover a fair bit of real estate.
A seiche is caused by rapid changes in barometric pressure on a large body of water. The water will be 'pushed down' by high pressure or 'pulled up' by low pressure on the area where the changes are taking place. This sets up a 'bathtub slosh' effect that can go on for some time. The period of a seiche is usually about 20 minutes. The more extreme and rapid the changes in air pressure, the more extreme the seiche in height. The phenomena was first studied on Lake Geneva, and the word is thus old 'Swiss French" in origin.
There is always some seiche activity going on - but usually it is no more than an inch or so in height. However, thunderstorms can cause much bigger ones to develop. The biggest seiche I have ever seen occurred the day there were tornados about fifty miles south of us on Lake Huron. The bay emptied completely - about a four foot change. The boys had a glorious time that day running out to grab fish and turtles that had been left on the newly exposed beach.
I have also had the experience of standing on the dock on a hot and windless day and having the water well up so that the dock was covered and the water started flowing over our breakwall.
I thought I would post about this, because most people, when I mention that there is a 'tide-like' activity on our bay, have no idea what I am talking about. We had a bit of a seiche on the weekend that, while fairly small in level, serves to illustrate the differences it can make. The photographs are of our dock, and the thing to look for is the (home-made) mooring anchor that is off to the left of the dock. This seiche would have been about 6-8 inches.
![[Image: seiche2.jpg]](http://ca.geocities.com/shadow123@rogers.com/seiche2.jpg)
The photo above was taken when the seiche was 'out'. Below, a photo taken when the seiche was 'in'.
![[Image: seiche1.jpg]](http://ca.geocities.com/shadow123@rogers.com/seiche1.jpg)
That's all, folks. Nature study moment over. At least now when I mention seiches and wax enthusiastic about a 'big' one, you will know what I am talking about.
One of the natural phenomena that I see at the cottage on a regular basis is the seiche. It is easily noticed at our location because the bay is shallow, with a very gentle gradient to deeper water; a change of a few inches in water depth can cover or uncover a fair bit of real estate.
A seiche is caused by rapid changes in barometric pressure on a large body of water. The water will be 'pushed down' by high pressure or 'pulled up' by low pressure on the area where the changes are taking place. This sets up a 'bathtub slosh' effect that can go on for some time. The period of a seiche is usually about 20 minutes. The more extreme and rapid the changes in air pressure, the more extreme the seiche in height. The phenomena was first studied on Lake Geneva, and the word is thus old 'Swiss French" in origin.
There is always some seiche activity going on - but usually it is no more than an inch or so in height. However, thunderstorms can cause much bigger ones to develop. The biggest seiche I have ever seen occurred the day there were tornados about fifty miles south of us on Lake Huron. The bay emptied completely - about a four foot change. The boys had a glorious time that day running out to grab fish and turtles that had been left on the newly exposed beach.
I have also had the experience of standing on the dock on a hot and windless day and having the water well up so that the dock was covered and the water started flowing over our breakwall. I thought I would post about this, because most people, when I mention that there is a 'tide-like' activity on our bay, have no idea what I am talking about. We had a bit of a seiche on the weekend that, while fairly small in level, serves to illustrate the differences it can make. The photographs are of our dock, and the thing to look for is the (home-made) mooring anchor that is off to the left of the dock. This seiche would have been about 6-8 inches.
The photo above was taken when the seiche was 'out'. Below, a photo taken when the seiche was 'in'.
That's all, folks. Nature study moment over. At least now when I mention seiches and wax enthusiastic about a 'big' one, you will know what I am talking about.
)
I *think* I have it fixed now. 
