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Impact #382, April 2005
Do Tsunamis Come in Super-Size
by William A. Hoesch and Steven A.
Austin*
(*William Hoesch, M.S. geology, is
Research Assistant in Geology, and Steven Austin, Ph.D.
geology, is Chairman of the Geology Department, both at
ICR.)
Fast-food consumables like french fries are known to come
in "super-size." According to Hollywood,
tsunamis do also. But is there scientific evidence for
super-size tsunamis in the past? The Indian Ocean tragedy
has brought attention to the fact that these large water
waves rank among earth's most severe natural disasters.
Because water is incompressible, disturbance at the ocean
floor generates a surface wave. In deep water such waves
propagate at speeds (celerity) as high as 800 kilometers
per hour, and their passage through the deep ocean is
barely perceptible. As water depths shallow, however,
wave energy becomes packed into a smaller column of
water, the wave slows, or "shoals," and its
form builds to fearsome proportions.
The Indian Ocean Tsunami of 2004
The catastrophe began on December 26, 2004, with a
magnitude 9.0 earthquake in the deep-water Sunda Trench
offshore Sumatra. Within 3-4 minutes, a 1200
kilometer-long rupture opened the seafloor, and a region
roughly the length and half the width of California was
displaced vertically by about two meters. The work
involved is a measure of the raw energy imparted to the
tsunami. In this case, it was equivalent to about 100
Hiroshima-sized atomic bombs. Directly east of the
epicenter lies the coastline of Sumatra's Aceh province
which experienced wave run-ups as high as 30 meters above
sea level (height of a ten-story building). Across the
Indian Ocean, the Sri Lanka coast received devastating
waves with run-ups to 10 meters. Hollywood imagery of
steep-fronted and curling waves may appear spectacular,
but are generally not true. Rather, tsunamis are best
likened to an advancing plateau of water, and the shape
of the wave front has probably less significance than the
mass of water behind it. Both the rushing waves and
receding waves do geologic work, creating distinctive
sedimentary deposits.
Earthquake-generated Waves
Four mechanisms are responsible for most, if not all,
tsunamis: earthquake, landslide, volcano, or
extraterrestrial impact. The Indian Ocean tsunami was an
example of the earthquake-generated type, but there have
been many others. In 1775 a big wave struck Lisbon,
Portugal, following an estimated 8.7M earthquake that
reduced that nation's shipping industry and navy to a
shambles overnight. A seismically active deep-sea trench
very similar to the Sunda Trench seems poised off the
Washington-Oregon coast. Evidence for several tsunami
strikes over the past few hundred years has been found by
geologists in the coastal marshes of the Pacific
Northwest.2 The tsunamis in these cases were probably
comparable in size to the December 26, 2004, Indian Ocean
event.
Shallow-focus earthquakes, the kind that generate most
tsunamis, seem to be size and energy limited. Deep-focus
earthquakes, on the other hand, are generated by an
entirely different process. Low density minerals (like
olivine) can transform to higher-density minerals (like
spinel and perovskite), abruptly changing the volume of
rocks.3 Volume reduction associated with this sudden
phase-change is capable of delivering an immense seismic
jolt. Historic deep-focus earthquakes may represent mere
residual stresses left over from much greater,
planet-wide plate movements that are modeled to have
accompanied the Genesis Flood. Magnitude-13 earthquakes
and greater are conceivable during this time of
theoretical whole-mantle overturn.4 Herein lies a
mechanism for generating "super-size" tsunamis
in the past.
Landslide-generated Waves
Big waves that struck the sparsely populated Newfoundland
coast in 1929 and the north coast of Papua New Guinea in
1998 testify to landslide processes. Landslide scarps and
debris deposits from both tsunamis have been located on
the ocean floor.5 Thus, the evidence for past tsunamis
can be found by wash marks on shore, or, indirectly, in
the form of large landslides, scarps, and debris piles
lying on the deep ocean floor.
Landslide debris covers the mostly underwater Hawaiian
Ridge over an area that is five times greater than the
area of the Hawaiian Islands themselves.6 Individual
landslides have been identified that are as large as
17,000 cubic kilometers. Underwater mapping reveals a
lumpy appearance to the deposits that is strikingly
similar to that left by the 1980 Mount St. Helens
landslide, only 1000 times larger.
Tsunami wave field in
the Bay of Bengal. View to the north west, focused near
the earthquake epicenter (northern Sumatra).US
Geological Survey
These landslides must have traveled
underwater at speeds on the order of 100 kilometers per
hour and unquestionably caused monstrous tsunamis. But
how big were they? Basalt cobbles and reef debris found
375 meters above present sea level on the island of
Lanai, testify that waves ten times the height of those
that recently struck Sumatra washed the debris onto the
Hawaiian mountainsides. Similar landslide debris offshore
from both New Jersey and Oregon testify of enormous past
tsunamis that struck the U.S. mainland.7
The largest landslide-generated tsunami appears to have
occurred when the entire continental shelf surrounding
the Gulf of Mexico gave way, and produced 200-meter-plus
tsunamis across that region.8 The trigger for this
simultaneous collapse across such a large area is
postulated to have been the Chicxulub (extraterrestrial)
impact on Mexico's Yucatan peninsula. Some of North
America's largest oilfields owe their existence to
sediments moved by this tsunami.9 Oilfield geologists
take catastrophic geology seriously in the Gulf region.
Volcanic-collapse Generated Waves
Large composite-cone volcanoes usually collapse inward
after eruption and form a crater like depression called a
caldera. If near sea level, the sudden rush of ocean
waters into a hot and instantly formed caldera can
generate impressive tsunamis. The crater left by the
explosion of Krakatoa (1883) in Indonesia's Sunda Strait
measures about 5 kilometers by 6 kilometers. The sudden
infilling of this caldera with seawater is the probable
cause for tsunami wave runups of 37 meters on neighboring
coastlines that killed 36,000 people. Santorini Volcano
in the Aegean Sea erupted explosively around 1490 B.C.,
and left a caldera of about 8 by 11 kilometers, over ten
times the collapsed volume of Krakatoa. Sea-borne pumice
deposits 250 meters above sea level on the nearby island
of Anaphi, and an unusual deep-sea deposit tens of meters
thick across much of the eastern Mediterranean, have both
been attributed to the Santorini tsunami.10 Globally, at
least 37 volcanic craters are known to be more than ten
times bigger than Santorini and Krakatoa, and many of
these are found at, or near sea level.11 Certainly
volcanic-collapse generated waves, including some of
super-size, played a major role in earth history.
Impact-generated Waves
Craters and suspected craters have been found in
continental margins that record at least 18 large
asteroid or comet impact events.12 Despite the lack of
historical precedent, tsunamis of potentially super-size
by impact have occurred in the past. The
90-kilometer-diameter Chesapeake Bay structure lies
beneath 400-500 meters of coastal sediments in
northeastern Virginia.13 Seismic imagery reveals a near
circular crater as deep as Grand Canyon and encompassing
an area twice that of Rhode Island. Waters that rushed
into this instantly formed crater must have generated
outward-bound waves with initial or "primary"
heights of up to 500 meters, modeling predicts, which
probably put the Appalachian foothills underwater.
Impacts of much larger proportions struck when most of
the continent was under water, probably during Noah's
Flood. Across a 10,000 square kilometer area in southern
Nevada, disrupted limestone blocks and as many as five
graded beds occur, as if great tsunamis sorted debris by
size.14 The Manson impact structure, located in
north-central Iowa, also took place when the continent
was underwater, and is associated with a widespread
limestone tsunami deposit.15
Do Tsunamis Have a Size Limit?
Life on our blue planet has had to cope with tsunamis of
super-size, even in human history. Science has discovered
this fact. What is the size limit for tsunamis? An
ancient text says, "In the six hundredth year of
Noah's life, in the second month, the seventeenth day of
the month, the same day were all the fountains of the
great deep broken up, and the windows of heaven were
opened" (Genesis 7:11). The text provides the date,
the duration, the depth and the extent of a seafloor
disturbance that began a Flood affirmed to be worldwide
by the prophet Moses, the Lord Jesus Christ, and the
apostle Peter. If this really happened in the fabric of
space-time history, it surely would have created the
greatest of tsunamis. As the people of South Asia pick up
the pieces from the Indian Ocean catastrophe, perhaps
they will discover a new and unique perspective on this
passage of Scripture. May they find the Ark of salvation
that is in the Lord Jesus Christ.
Endnotes
1. Tsunami energy of 8 x 1015 joules is estimated from
disturbance map in: Science News, Jan. 8, 2005. Total
energy of the earthquake is 2 x 1018 joules.
2. Atwater, B. F., 1987, Evidence for great Holocene
earthquakes along the outer coast of Washington state:
Science, 236:942-944.
3. Dabler, R., and D. Yuen, 1996, The metastable oliv-ine
wedge in fast subducting slabs: Constraints from
thermo-kinetic coupling: Earth and Planetary Science
Letters, 137:109-118.
4. Baumgardner, J., 2003, Catastrophic plate tectonics:
The physics behind the Genesis Flood, in R. L. Ivey,
editor: Proceedings of the Fifth International Conference
on Creationism, Creation Science Fellowship, Pittsburgh,
PA, pp. 113-126, also in http://globalflood.org.
5. Monastersky, R., 1998, Waves of death: why the New
Guinea tsunami carries bad news for North America:
Science News, Oct. 3, 1998.
6. Normark, W. R., and others, 1993, Giant
volcano-related landslides and the development of the
Hawaiian Islands: United States Geological Survey
Bulletin, 2002:184-196.
7. Driscoll, N. W., and others, 2000, Potential for
large-scale submarine slope failure and tsunami
generation along the U.S. mid-Atlantic coast: Geology,
28:407-410; and C. Goldfinger, and others, 2000,
Super-scale failure of the southern Oregon Cascadia
margin: Pure and Applied Geophysics, 157:1189-1226.
8. Bralower, T. J., and others, 1998, Cretaceous-Tertiary
boundary cocktail: Chicxulub impact triggers margin
collapse and extensive sediment gravity flows: Geology,
26:331 -334.
9. Including the giant Canterell field (17 billion
barrels, original reserves) and others in Mexico's
prolific Campeche Platform: J. M. Grajales-Nishimura and
others, 2000, Chicxulub impact: The origin of reservoir
and seal facies in the southeastern Mexico oil fields:
Geology, 28:307-310.
10. Yokoyama, I., 1978, The tsunami caused by the
prehistoric eruption of Thera, in Thera and the Aegean
World I: Santorini, Greece, Second International
Scientific Congress, pp. 277-283; and M. Cita, and
others, 1996, Deep-sea tsunami deposits in the eastern
Mediterranean: new evidence and depositional models:
Sedimentary Geology, 104:155-173.
11. Mason, B., and others, 2004, The size and frequency
of the largest explosive eruptions on earth: Bulletin of
Volcanology, 66:735-748.
12. Dypvik, H., and L. Jansa, 2003, Sedimentary
signatures and processes during marine bolide impacts: a
review: Sedimentary Geology, 161:309-337.
13. Poag, C. W., and others, eds., 2004, The Chesapeake
Bay Crater: Springer, New York, 522 pp.
14. Warme, J. E., and H. C. Kuehner, 1998, Anatomy of an
anomaly: The Devonian catastrophic Alamo impact breccia
of southern Nevada: International Geology Review,
40:189-216.
15. Hartung, J. B., and R. R. Anderson, 1996, A brief
history on investigations of the Manson impact structure,
Geological Society of America, Special Paper 302, pp.
31-43.
© 2005 by ICR. Reprinted with permission. All Rights
Reserved. Single Copies 10$. Order from: INSTITUTE FOR
CREATION RESEARCH P.O. Box 2667, El Cajon, CA 92021.
Available for download on the ICR website (www.icr.org).
TSS
May
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