lake tahoe tsunamiLake Tahoe Tsunami simulation from Tsunami that occurred 7,000 to 15,000 years ago.

Could there ever be a damaging tsunami on Lake Tahoe? In the words of Fargo’s Sergeant Marge Gunderson “you betcha!” but such a wave wouldn’t actually be a tsunami, it would be a seiche.

What exactly is a seiche? I’ll give you two clues – it’s not exactly a tsunami, and it’s definitely not a tidal wave. A seiche is a standing wave on a freshwater lake or in a semi-enclosed harbor on the ocean. The word ‘seiche’ is often used interchangeably with ‘tsunami’ and ‘tidal wave,’ but all three refer to different phenomena.

The Japanese translation of ‘tsunami’ is literally ‘harbor wave,’ but in the modern era, ‘tsunami’ is used colloquially to refer to the devastating ocean waves and surges that crash hundreds of yards inland as a result of gigantic underwater earthquakes in places like Indonesia, Thailand, and Japan. The use of the word ‘tsunami’ in referring to damaging waves came about in ancient Japan when waves appeared seemingly out of nowhere and caused grave damage to harbors. Eventually, people started to realize that tsunami waves were caused by underwater earthquakes, and were not tidal waves, because they have nothing to do with tides. Given what happened in Japan just a few months ago, I probably don’t need to describe the horror and destructive potential of these waves since they are so fresh in all of our minds.

Stranded Boat from the Sendai earthquake and tsunami in Japan (from National Geographic)

Weather-caused seiches are regularly observed in the Great Lakes, including Lake Erie where they occur often and are up to 5 feet in height. The National Weather Service even issues warnings for them when they cause water fluctuations of 2 feet or more. In July of 1995, a seiche on Lake Superior caused the water level to drop by 3 feet in fifteen minutes, leaving some boats dangling from docks (Korgen, 2008).

Seiches  can be just as devastating as tsunami waves are in the ocean. What causes seiches? Seiches are caused by earthquakes, landslides, prolonged wind events, meteorite impacts, and gradients between large areas of high and low pressure on either side of the body of water. Anything that can establish resonation on the surface of water in a lake or harbor can cause a seiche. The relatively short cross-shore distances compared to the ocean can cause seiche waves to be reflected back and forth across lakes for hours and hours. As you might imagine, this could be very bad for things and people that call the shores of lakes home.

Lake Tahoe has suffered from these destructive waves in the past. Deep into the past as far as humans are concerned, but barely a moment ago in terms of geologic time. A 2006 USGS study led by internationally recognized tsunami expert James G. Moore found that a giant landslide in McKinney Bay on Tahoe’s west shore dropped several cubic miles of the West Shore 1,500 feet to the bottom of the lake and likely generated enormous seiche waves between 7,000 and 15,000 years ago (Moore et al., 2006).

Faults beneath lake Tahoe, mapped by Graham Kent and colleagues in 2004 (SF Chronicle).

Another group of scientists led by Graham Kent of Scripps Institute of Oceanography mapped and described several major faults running underneath Lake Tahoe in 2005 (Kent et al., 2005, see map above), and declared them capable of producing an earthquake as large as M 7.0 that could in turn cause seiches between 10 and 30 feet in height. John Anderson and Gene Ichinose of the UNR seismological laboratory studied the faults underneath the lake and they estimated that the probability of such an event would be around 2-4% in the next 50 years, or in other words, minute (Ichinose, 2000).

If Tahoe did suffer from a large earthquake that suddenly slammed up the lakebed, or angered local telemarking hippies and caused a giant chunk of Jake’s Peak to slide into the lake, the consequences would be devastating for just about everything and everyone on or a few hundred feet back from the shores of the lake. Imagine a three story wall of freezing cold water smashing ashore in Tahoe City, Incline Village, or South Lake Tahoe. Buildings would be smashed into bits, people wouldn’t stand a chance.  Waves would crash around the lake for hours, ricocheting off the shores and amplifying in places like Emerald Bay and Meek’s Bay. Giant trees would be snapped like twigs, and huge volumes of water would overtop the dam in Tahoe City and rush down the Truckee River through Truckee and down into Reno.

YouTube Preview Image

The above video shows one interpretation of the giant pre-historic McKinney landslide and the ensuing seiche waves superimposed on a digital elevation model of modern Lake Tahoe.

In the end though, planning for the worst case scenario is not as important as preparing for low consequence, high-probability natural hazards up here in Tahoe, such as wildfires. Seiche waves could strike on lake Tahoe, but the chances are more on par with a meteorite falling from outer space and crashing into your house. So before you go installing a titanium-kevlar roof to protect yourself, or selling your 3,500 square foot lakeside mansions and moving to Truckee, you might be better off developing an emergency evacuation plan in case you have to drop everything and run from an approaching wildfire.

What other earth-science question or questions do you have? Post them in the comments and I’ll pick one to answer in next week’s column.

References

Ichinose, G. A., J. G. Anderson, K. Satake, R. A. Schweickert, M.L. Lahren. (2000). The potential hazard from tsunami and seiche waves generated by large earthquakes within Lake Tahoe, California-Nevada. Geophysical Research Letters 27(8):1203-1206

Kent, G.M.; J.M. Babcock, N.W. Driscoll, A.J. Harding, J.A. Dingler, G.G. Seitz, J.V. Gardner, L.A. Mayer, C.R. Goldman, A.C. Heyvaert, R.C. Richards, R. Karlin, C.W. Morgan, P.T. Gayes and L.A. Owen (May 2005). “60 k.y. record of extension across the western boundary of the Basin and Range province: Estimate of slip rates from offset shoreline terraces and a catastrophic slide beneath Lake Tahoe”. Geology 33 (5): 365–368. doi:10.1130/G21230.1

Korgen, Ben. Bonanza for Lake Superior: Seiches Do More Than Move Water.

Moore, J. G., R. A. Schweickert, J. E. Robinson, M. M. Lahren, C. A. Kitts. (2006). Tsunami-generated boulder ridges in Lake Tahoe, California-Nevada. Geology 34(11):965-968.

Schweickert, R. A.; M. M. Lahren. (2002). Glacial Geology of Blackwood Canyon, Lake Tahoe, California; Implications for Landslides and Tsunamis. Abstracts with Programs – Geological Society of America 34(6):130-131.

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22 Comments

  1. Andy Coughman says:

    I don’t know 2-4% in the next 50 seems pretty good to me!

    Reply
  2. Tim Konrad says:

    Great Post Dr. Kaye
    Here is a question,
    I have heard that the adirondack mountains of New York were once the size of the Himalayas. Is this true? What other mountain ranges were once far larger then their current size?

    Reply
    • Mine is Bigger says:

      the north shore of minnesota along lake superior used to be bigger in the rockies.

      Reply
    • NH Res says:

      To answer the first question: This fact is true. The Appalachian Mountain Range (which the Adirondack’s are a part of) was formed about 300 million years ago when Pangaea (land mass consisting of all the present day continental plates) existed. The Appalachians were formed by the collision of the South American, African, and North American continental plates, which is analogous to the Himalayan Mountain range being formed by the convergence of the Eurasian and African plates. Due to the extreme size of land which were converging in Pangaea, it is estimated that the Appalachian Mountain range would have reached the approximate height of the present day Himalayan Mountains.

      Reply
    • NH Res says:

      On to the second Question. For the Most part, The major mountain ranges of the united states were at one point higher than they are now. The majority of these ranges were “built up” tens of millions of years ago. However, one of the greatest mountain destroyers are glaciers. Since the last glacial period was about 22,000 years ago, glaciers have been able to rip apart the ranges of the US, bringing their elevations down significantly. Since you added these two questions together, ill take it that you were wondering if any of the other US ranges were also as high as the Himalaya. The answer is no. Since the formation of other ranges such as the Cascades, Rockies and Sierras, were either formed through different processes, or involved less quantities of mass upon convergence of plates, there is no way they could have reached elevations of the Himalayas.

      Reply
    • Bill says:

      The Ozark Mountains in Southern Missouri used to be quite large also.

      Reply
  3. scrotie mcboogerballs says:

    How big is the universe?

    Reply
  4. skier says:

    why am i hung like a horse?

    Reply
  5. heckler groupie says:

    What caused Chimney to be as marvelous as it currently is?

    Reply
  6. serious says:

    Time to wax up the surfboards!

    Reply
  7. Squawbear says:

    Heckler would probably shred that wave

    Reply
  8. 530SKIR says:

    West Shore the Best Shore…..

    Reply
  9. Cupcake Ice Cream says:

    How many licks does it take to get to the center of a toosie pop?

    Reply
  10. Agent P says:

    Wet whore the best whore????

    Reply
  11. snowgoddess402 says:

    One more reason to live in Truckee.

    Reply
  12. Heckler says:

    Haha!
    …….and you know I’d surf that shit.

    Reply
  13. pjeuck says:

    Technically there are two phenomena transpiring in Lake Tahoe, a tsunami and a seiche. The landslide caused the initial wave, which is technically correct, a tsunami. Since Lake Tahoe is a relatively small body of water when compared to an ocean, the initial tsunami wave created by the landslide sloshes around, like how one can slosh water in a bath tub, oscillating to the natural harmonics of the lake’s basin. The resulting sloshing following the initial wave reflecting off the shorelines is the seiche. So there are two phenomena occuring.

    Seiches in smaller water bodies, suhc as the Great Lakes, Bay of Fundy, etc. can result from the force of a persistent wind, or stormns. If the natural geometry of the basin is in harmonic resonance with the driving forces seiches can cause significant shifts in water level, with a relatively small dirving force. Fill a bathtub and move you hand back and forth in harmonic sequence with the slosh in the tub and it wont take much force to get a larger and larger slosh that may spill over the top of the tub. Certain water bodies also repsond to natural forces like storms and persistant winds to create harmonic sloshing similar to that you can create with your hand in a tub, only on a larger scale. Seiches are therefore a different phenomena than tsunamis although in a given water body both phenomena could occur, with the initial landslide/tsunami being the driving force (hand in the tub) that creates a resulting seiche in harmonic resonance that is determined by the water body’s geometric features. So the article is not exactly correct by saying that only a seiche is occuring. The tsunami-seiche combination/system of Lake Tahoe makes the situation more complicated and potentially more devastating than a tsunami alone.

    The ocean is too large for a seiche to be a factor following a tsunami. The engery is spread over too lareg an area and the energy attenuates so that no harmoic oscillation occurs following a tsunami in the ocean. However in a tsunami there is always a series of waves and not just one. Thorw a rock in a still pond and a series of waves propagates out from the center spreading out in circular rings. Tsunamis are like throwing stone in a pond, except at a much larger scale. With a tsunami the waves hit obne after another until the last ring passes. In a seiche like the phenomena that could occur in Lake Tahoe, the waves tsunami waves spreading out from the initial disturbance (the landslide) will reflect and interact with the seiche wave/sloshing relfected off the shore lines creating high points and low points. If one watches a motor boat make a shap 180 degree trun in a lake, one will observe the wake waves from the boat criss crossing at nearly right angles from each other. These interacting waves make high points and low points, called nodes. These nodes are where the two wave trains either build each other up, or cancel each other out creating nodal elevation changes in the waters surface. These can happen in a much larger scale in lake tahoe then causing some waves to amplify and buildup to much greater height than if there were no wave interaction at all. So the tsunami seiche combination in a place like Tahoe could hold far greater consequences than a comparable earthquake/landslide would cause in the ocean where a seiche would not form.

    I don’t know if this makes things any clearer, but the article only partially explains the natural phenomena that has taken place in Lake Tahoe in the past and not the lareger more complex situation.

    Reply
  14. hikarl says:

    I have seen rooted pine trees in Tahoe much deeper than the current water level. What is the relatively recent water level history of the lake?

    Reply

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