Captions

Top Right:  The most severe Great Lakes seiches are caused by  fast-moving squalls with strong atmospheric pressure that pushes down the surface water.  The downward pressure displaces water, sending waves towards the shore and causing the lakes to slosh back and forth.

1.  Squall line moves in rapidly over lake.

2.  Storm dumps rain and exerts atmospheric pressure on lake's surface.

3.  Atmospheric pressure on lake creates a seiche, sending waves toward the shore ahead of the rain showers.

Bottom Right:  A seiche triggers waves that cause water levels to rise in one area as they drop in another part of the lake.

Article:  Big Lake 'tsunamis'  - Jeff Alexander

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