Weather by Malcolm RileyMeteotsunamis and the Loch Ness monster

The Meteotsunami phenomena (Afloat last month) can be experienced in large lakes around the world. A meteotsunami in Lake Michigan in 1954 was estimated to be in the vicinity of two metres and swept seven people to their death from the Chicago waterfront.
Meteotsunamis in lakes are usually caused by the wind pushing water to one side of the lake. The water builds up on the windward side of the lake while the wind keeps blowing. If the wind drops or changes direction significantly the water sloshes back to the ‘shallower’ shore. This phenomenon is marked in long deep narrow lakes that are often glacial in origin.
Many lakes in the world are deep enough for several separate layers of water to form.
The near surface layer (epilimnion) down to about five to ten metres is constantly mixed by the heating from the sun and wave action and is relatively warm. The layer below the near surface layer drops in temperature very rapidly, this is called the thermocline. Below the thermocline is a layer of cold water down to the lake bottom whose temperature is almost uniform (hypolimnion).
Weather by Malcolm Riley - Meteosunamis and the Loch Ness monsterWind builds up water on the windward side of the lake. This extra weight of the water pushes the thermocline down on this windward side of the lake and it rises on the opposite side.
When the wind relaxes the weight is taken off the windward part of the thermocline and it is the cold water deep in the lake that sloshes backwards and forwards.
There is little indication on the surface of the lake that anything is happening. Deep in the lake waves of up to nine metres between the layers of water have been recorded (on some lakes). While this may be a hard concept to relate to waves between two liquids, a similar process occurs in novelty paperweights. The liquid in these paperweights is a mixture of different densities; oil and water. The concept is basically the same as that in the lake.
Weather by Malcolm Riley - Meteosunamis and the Loch Ness monsterAn interesting aside to this phenomenon is that the large underwater waves can pick up debris from the bottom of the lake such as an old blackened tree limb with some lake growth on it. The wave can give this debris enough vertical inertia that it will rise to the surface, move along the surface for a distance and then slowly sink.
This is one of the theories to explain lake monsters such as Nessie and the Champ monster from Lake Champlain in the USA.