The water speed has been measured at over 20 knots, and more than 3, m3 of water flow across the entrance to the fjord every second. Saltstraumen is very rich in fish, some of which are famously big. When the tide goes out, the water moves to a place between the sun and the moon which is out at sea, away from the beach. When the tide comes in the water moves to a place between the sun and moon which is over land. When this happens, the bulge of the ocean caused by the sun partially cancels out the bulge of the ocean caused by the moon.
This produces moderate tides known as neap tides, meaning that high tides are a little lower and low tides are a little higher than average. Why do some places have only one high tide and one low tide in a day? Wind and weather conditions on the Great Lakes may create a seiche , an oscillating wave which can be several feet high. As this is very similar to the six-hour time period of the tides on the ocean, it is frequently mistaken for a tide. Do the Great Lakes have tides?
Water levels in the Great Lakes change primarily because of meteorological effects. Search Our Facts. One antinode is the wave peak or crest when the other is the wave trough.
In the simple diagram below, at one instant, the left antinode is the peak while the right one is at the trough. After half an oscillation, the positions of peak and trough will be reversed. A seiche may have many nodes, in theory an infinite number but in reality rarely more than a handful.
In a two-node seiche, the antinodes will be found at the shores and the center of the basin with nodes halfway between the shore and center points. With the two-node seiche, the shoreline antinodes are in synch, either rising or falling together, and the mid-lake antinode is in opposition, cresting when shore antinodes are in troughs, and troughing when shore antinodes crest.
In general, the fewer the nodes and shallower the basin, the more pronounced the difference in water levels between crest and trough. Lakes usually have characteristic periods of oscillation, related to the water depth, number of nodes and the cross-basin distance over which the seiche moves.
On the Great Lakes the period between seiche peaks ranges from minutes to more than eight hours, depending on the location where the seiche forms. The typical seiche across Lake Erie has a period of around 14 hours. For other lakes, the period is shorter, for example, in Lake Champlain in upstate New York, 4 hours; Scotland's Loch Ness, about 30 minutes.
Large seiches are powerful enough to present hazards to navigation, damage to moored boats, piers and waterside facilities, and flooding dangers to shoreline communities. Because they often arrive unannounced, seiches present a danger to those working or playing near the shoreline, particularly on docks and piers. At times they can turn deadly. On June 26, , a seiche 2. Eight people were killed, most of whom were swept into the water and drowned while fishing in Montrose Harbor.
On July 4, , at least ten beach-goers were killed in a similar incident along Lake Michigan's eastern shore. On July 13, , a Lake Superior seiche of about a metre 3 ft in amplitude left boats hanging on their mooring lines from the docks when the lake water suddenly retreated. The same weather system set up seiches on Lake Huron as well. In a seiche in Two Harbors, Minnesota, caused several hundred thousand dollars damage to iron-ore vessels loading at the Duluth Missabe Iron Range Railway docks.
Seiches have been experienced by geocachers and others at this cove. What predominant feature of this area would lead to a "Seiche"? How often do you think a "Seiche" would occur in this location? For a "Seiche" to occur in this location from what direction would the wind need to be blowing from? What would the primary condition on Lake Superior that would lead to a "Seiche"?
Depending on the season when you visited the earthcache location, there is evidence that a seiche has occurred at this location: 5. During the winter, there are two main pieces of evidence, which can only be found near the cache location, that show that a seiche has taken place in the area. What are they?
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