In that seiche, lake water went out and came back within fifteen to twenty minutes at Ashland, Wisconsin, Marquette and Point Iroquois, Michigan, and Rossport, Ontario. People who witnessed it were amazed. In just a few minutes, water levels changed about three feet. In 1998 a seiche occurred in Two Harbors, Minnesota, that caused several hundred thousand dollars of damage to vessels loading iron ore at the Duluth Missabe Iron Range Railway Company docks. Just last December, another large seiche occurred in the Duluth-Superior harbor.
Seiches generate currents within the lake's water column.
The strengths of these currents depend on the sizes of the seiches driving them. The smallest seiches drive currents with no significant effect on vessel navigation. The biggest seiches drive strong and unpredictable currents that can move vessels off course and aground or otherwise into harm's way. Seiche-driven currents do more than disturb moored vessels and influence navigation. They can impact lake biology.