Could a tsunami occur in Lake Erie?
Public awareness of the horrible consequences of an earthquake-generated tsunami increased dramatically after the December 26, 2004, tsunami in the Indian Ocean, which was propagated by a 9.0-magnitude earthquake near the northwest coast of Sumatra. Many people have wondered if such an event, even on a much smaller scale could occur in Lake Erie. The short answer is that the probability is very, very low.
An earthquake-generated tsunami in Lake Erie would require a very large earthquake, probably 7 magnitude or above, and significant vertical displacement of the lake bed and/or displacement of a large amount of sediment or rock that would flow downslope, either from above water or below water. Let's examine each of these criteria.
- Large earthquake: Historically, in the Lake Erie region, we have not seen earthquakes in the 7-magnitude range; indeed, the largest ones are moderate earthquakes in the 5-magnitude range. However, our historical record is quite short, geologically speaking, so we cannot say with absolute certainty that a larger earthquake could not occur. Some seismologists have suggested that the Akron Magnetic lineament could generate an earthquake in the 6.5-magnitude range, but preliminary analysis of post-glacial sediments in the region have not yielded evidence of a large earthquake in the last few thousand years.
- Vertical displacement of the lake bed: Earthquakes in the Lake Erie portion of Ohio, for which sufficient data are available, show primarily horizontal (strike-slip) movement rather than vertical movement (normal or reverse). This would suggest that even an earthquake larger than has been seen historically would not cause significant vertical displacement of the lake bed and thus would not generate a tsunami wave. In addition, some tsunami experts suggest that a substantial column of water (deep water) must overlie the displaced fault to create a sizable wave. Lake Erie, of course, is very shallow.
- Displacement of rock or sediment: Tsunamis can be generated by the downslope movement of a very large volume of rock or sediment, either from a rockfall above the water or from a submarine landslide. Commonly, such slides can be triggered by large earthquakes. Although large amounts of unconsolidated sediments are washed into the lake each year when shoreline bluffs are undercut by wave action, these masses lack sufficient volume and rapid collapse to displace a volume of water that would create a tsunami. Lake Erie, the shallowest of the Great Lakes, has a very gentle bottom profile, particularly in the western and central basins, which border Ohio. The eastern basin, the deepest part of the lake, has steeper slopes but probably not steep enough for a large amount of sediment to suddenly flow downslope in a submarine landslide.
From these data, we can conclude that it is very unlikely that Lake Erie would experience a tsunami. There are several recorded instances of so-called "rogue" waves that have suddenly swamped a comparatively small area of Lake Erie shoreline. None of these events have been associated with earthquakes and all have been confined to a local area of shoreline. Although these events are poorly understood, it is thought that they are caused by local but intense atmospheric disturbances.
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