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EVIDENCES FOR RAPID FORMATION AND FAILURE


OF PLEISTOCENE "LAVA DAMS" OF THE
WESTERN GRAND CANYON, ARIZONA

SCOTT H. RUGG
RUGG & ASSOCIATES
1221 OLIVER AVE.
SAN DIEGO CA 92109STEVEN A. AUSTIN

INSTITUTE FOR CREATION RESEARCH
10946 N. WOODSIDE AVE.
SANTEE CA 92071

Presented at the Fourth International Conference on Creationism
Pittsburgh, PA, August 3-8, 1998


ABSTRACT


Over 200 isolated outcrops of horizontally stratified, basaltic
lava flows within the inner gorge of western Grand Canyon indicate
that several natural "lava dams" blocked the flow of the Colorado
River during the Pleistocene, resulting in the formation of
several lakes within the canyon. The largest lake was 90 m above
the high water level of present-day Lake Powell and backed up a
distance of over 480 km to Moab, Utah . Although early studies
indicated that three or less dams once blocked the inner gorge,
work completed in 1994 indicated that at least 13 distinct lava
dams may have blocked the Colorado River. Comparison with modern
erosion rates of cliff retreat (Niagara Falls) indicate that the
13 dams would have required a minimum of 250,000 years to erode
during the Pleistocene. However, geologic features and
relationships not previously considered indicate that the dams
formed rapidly (hours, days, or months) and failed
catastrophically soon after formation. Excess radiogenic argon is
contain within many basalts of Grand Canyon. This initial argon
invalidates K-Ar model ages which are assumed by many geologists
to require an age of more than one million years for the oldest
lava dams. We envision that the entire episode of the lava dams
can easily be reconciled within a time-frame of less than two
thousand years. Our observations and interpretations reveal
serious flaws in the current long-age time-scale of the
Pleistocene Epoch.

INTRODUCTION

The western Grand Canyon contains a unique and spectacular sequence
of Pleistocene volcanic flows. The basaltic flows are particularly
captivating because of their stark contrasting jet-black color
against the light brown and red hues of the underlying Paleozoic
sedimentary rocks. The Pleistocene flows appear as "frozen" lava
falls cascading down the walls of the inner gorge to the Colorado
River below. They also have a much more unique aspect which was
first observed by John Wesley Powell in 1887. Powell noted that many
of the inner gorge flows are horizontally bedded, indicating that
they once extended across the entire width of the inner gorge,
damming the Colorado River and forming an immense lake within the
Grand Canyon. Later geologic studies showed that there were possibly
several separate lava dams within the western Grand Canyon during
the Pleistocene. Recently, W. Kenneth Hamblin [6] evaluated over two
hundred lava-dam remnants within the inner gorge between miles 177
and 254 (river miles measured downstream from Lees Ferry, Arizona -
See Figure 1) and concluded that at least 13 separate and distinct
lava dams once blocked the Colorado River spanning a length of time
between approximately 1.8 Ma (million years ago) to as recently as
0.45 Ma.

The remnants of lava dams outcrop at elevations from river level
(500 m) up to near the top of the inner gorge rim (1200 m),and vary
in size from a few meters to over 2.5 km long. The tallest and
oldest lava dam had a crest of 700 m above the Colorado River and
backed up a lake to near Moab, Utah (a distance of over 480 km)
which would have been 90 m above the high water level of present-day
Lake Powell. The dams were all at least several kilometers long,
with the longest extending a total distance of over 138 kilometers.
Based on present rates of retreat of Niagara Falls, Hamblin [6]
suggested that the individual dams required from 10,000 to 40,000
years to erode. Using an intermediate value of 20,000 years, Hamblin
[6] concluded that the Colorado River would have been dammed a total
of up to 250,000 years during the period between 1.8 Ma to 0.45 Ma
of the Pleistocene.

Lava dams figure prominently in the rendition of Grand Canyon in the
popular press. Hamblin and Hamblin [7] have recounted the
naturalists common perception of Grand Canyons lava dams being
"more than one million years old." Davis Young [17], a Christian
geologist writing about Noahs Flood, has reiterated the notion that
Noahs Flood could not have been involved in forming the Grand
Canyon, because the canyon was already present "1.16 million years
ago" when lava flowed in and blocked the river. Youngs very precise
"age" for the lava dam comes from potassium-argon (K-Ar) dating of
the basalt [12].

This long time-frame potentially presents a problem to those who
hold to a Biblical view of a young earth and a short time-frame for
Earth history. If the Pleistocene is a post-Flood epoch, then the
episode of the volcanic dams needs to be reconciled within only a
several-thousand-year time-frame, and not the "more than one million
years" of the uniformitarian time scale. Does the geologic field
evidence support a short or long time-frame scenario for the
development and subsequent erosion of the Pleistocene lava dams? We
believe that the evidence overwhelmingly supports a short
time-frame, and we will examine several important details not
previously considered.

Figure 1. Location and Geologic Map of Grand Canyon, Arizona.
GEOLOGIC SETTING

The volcanic rocks of the western Grand Canyon are part of the
Uinkaret Volcanic Field. This volcanic field extends northward from
the Colorado River approximately 80 kilometers to near the Vermilion
Cliffs, and contains up to 160 volcanic cones [8]. The cones range
from 15 to 250 meters in height. The volcanic flows are generally
less than 8 meters thick and cover an area of several hundred km2.
Maxson [10] noted that the volcanic rocks consist of olivine basalt
flows and basaltic cinders . The flows erupted in association with
two north/south trending fissures on the Uinkaret Plateau which
extend north from near the rim of the inner gorge. Only a few
relatively small eruptive sources occur on the platform south of the
inner gorge. The flows average between approximately 1 to 2 meters
thick. Some individual flows cover areas of up to several square
kilometers. The thin and extensive lateral coverage of the flows
indicates that they were highly fluid upon eruption. Many of the
flows poured southward into the inner gorge as lava cascades. The
most spectacular cascades occur between miles 179 and 182 on the
north wall of the inner gorge. One cascade (near mile 181) almost
reaches the bank of the Colorado River [2].

The classic Grand Canyon sequence of Paleozoic rocks (Tapeats
Sandstone through Kaibab Formation) all outcrop in the western Grand
Canyon. The rim of the inner gorge is composed of the Esplanade
Sandstone (Supai Group). The wall of this inner gorge exposes strata
as deep as Tapeats Sandstone. The broad Esplanade Platform occurs
above the inner gorge and is overlain by the Hermit through Kaibab
Formations.

The Toroweap and Hurricane faults are the most prominent structural
features of this region of the western Grand Canyon. The Toroweap
Fault, which crosses the Colorado River near mile 179, displays
about 250 meters of displacement and has controlled the development
of Toroweap Valley on the north side of the inner gorge and Prospect
Valley on the south. The Hurricane Fault exhibits up to 400 meters
of offset. The fault runs parallel with the Colorado River starting
at mile 188 (Whitmore Canyon) where the river makes a southward
bend, and eventually crosses the river near mile 191, where the
river makes another turn toward the west. Like Toroweap Valley,
Whitmore Canyon has allowed the lava flows on the Esplanade to be
channeled southward toward the inner gorge.

LAVA DAMS

McKee and Schenk [11] first studied the lava-dam remnants and
concluded that they were part of a large solitary dam structure.
After a more detailed study, Maxson [10] concluded that up to three
separate dams, two of which coexisted, once filled the inner gorge.
Hamblin [6] has concluded, in the most detailed study to date, that
at least 13 separate lava dams, none of which coexisted, filled the
inner gorge during a period between 1.8 Ma to 0.45 Ma of the
Pleistocene. Hamblin noted that the remnants displayed several
distinctive types of depositional features (texture and flow
thickness) which he relied upon to correlate the individual dam
remnants.

One of the most interesting aspects of the remnants is that many,
including some of the oldest, occur near the present elevation of
the Colorado River. For example, a large outcrop of Toroweap Dam
occurs within only 15 m of the present river level. This shows that
there has not been significant additional downcutting of the canyon
in this area since the time of formation of even the oldest dams.
The pattern of preservation of dam remnants also shows that the
inner gorge has not undergone noticeable widening during the
Pleistocene.

Concepts of uniformitarian geologists regarding the very long ages
of the lava dams within Grand Canyon come from three areas: (1) the
stratigraphic relationships of the different flow remnants of
ancient dams, (2) the durability of slopes within the canyon against
which these dams have accumulated, and (3) K-Ar dating of the
basalt. The first two methods are strongly tied to the geomorphic
presuppositions of the geologist making the interpretation. For
example, were multiple dams each eroded slowly at the rate at which
the Niagara River of New York is now eroding back the falls?. The
third (K-Ar dating) appears to be less dependent on geomorphic
presuppositions.

K-Ar Dating of Lava Dams

The first basalt dam to be dated using the K-Ar method was Toroweap
Dam by McKee, Hamblin and Damon [12]. The lowest part of that dam
gave a K-Ar model age of 1.16 +/- 0.18 Ma (million years). These
earliest workers admitted that their age could be in error because
of "excess argon", a process whereby the magmatic argon is occluded
within basalt as it cools making the sample appear exceedingly old.
Other investigators since have also dated basalts within Grand
Canyon. Hamblin [5, p. 199] described numerous basalt samples
collected during 1972 and dated by G. B. Dalrymple. Concerning these
rocks, Hamblin noted that four basalt flows gave "reliable dates"
(0.14, 0.57, 0.64, and 0.89 Ma). However, Hamblin noted "many had
excess argon" [5, p. 199]. The "ages" for those with "excess argon"
have not been reported in any publication. Also, there has been no
publication of which criteria were used to select the "reliable"
from the more-frequently occurring "unreliable" ages. Recently,
Wenrich, Billingsley and Blackerby [18, p. 10,421] reported other
"ages" for basalt dams within Grand Canyon, but none exceeds the
"age" of Toroweap Dam (supposedly 1.16 +/- 0.18 Ma).

In order to test the K-Ar dating of the lava dams, we collected
another sample of the Toroweap Dam about 300 meters downstream from
the site sampled by McKee, Hamblin and Damon [12]. Our new sample of
Toroweap Dam (called QU-16) comes from the north side of the river
just above Lava Falls Rapid (mile 179.4) at somewhat higher
elevation than the sample of McKee, Hamblin and Damon [12]. This new
sample is very fine-grained and uniform black, without phenocrysts
and without xenoliths. It may be classified as a "basanite" (44.3wt
% SiO2, 5wt% total alkalis and significant olivine). In every way it
appears suitable for K-Ar dating. The one-kilogram sample was milled
to -230/+270 mesh particles (63 to 53 microns) and separated into
heavy and light fractions by centrifugation in methylene iodide, a
heavy liquid "cut" to a specific gravity of 3.20 with ethyl alcohol.
The float fraction (called QU-16FG) is dominated by plagioclase and
glass. The sink fraction was separated magnetically into weakly
magnetic olivine (called QU-16HN) and strongly magnetic
orthopyroxene with some Fe-Ti oxides (called QU-16HM). The three new
samples were submitted to Geochron Laboratories (Cambridge,
Massachusetts) for conventional K-Ar analysis. The results are
listed in Table 1 and plotted graphically in Figure 2.

Table 1. Potassium and Argon Data for Toroweap Dam.

%K40K ppm% 40Ar*40 Ar* ppm40 Ar*/40K"Age" Ma
A-Flow0.94751.1303.10.780 x10-40.690 x10-41.19 +/- 0.18
QU-16FG1.4681.7515.93.49 x10-42.00 x10-43.4 +/- 0.2
QU-16HM0.6930.8265.01.49 x10-41.80 x10-43.1 +/- 0.3
QU-16HN0.2530.3025.03.65 x10-412.07 x10-420.7 +/- 1.3

New K-Ar analyses on the Toroweap Dam lava are listed with the
sample "A-Flow" (our name for the published data of McKee, Hamblin
and Damon [12]). We recalculated the abundance of 40K and the
resulting "model age" in "A-Flow" using the new constants [14]. The
recalculated age is 1.19 +/- 0.18 Ma. However, the three mineral
concentrates from sample QU-16 contain significantly more 40Ar* than
the whole rock analysis of "A-Flow". Mineral concentrates from QU-16
have 1.49 to 3.65 x 10-4 ppm 40Ar*, whereas "A-Flow" has only 0.78 x
10-4 ppm 40Ar*. "Model ages" for QU-16 are 3.4 +/- 0.2 Ma
(feldspar-glass), 3.1 +/- 0.3 Ma (orthopyroxene + FeTi oxides), and
20.7 +/- 1.3 Ma (olivine). These ages are strongly discordant with
that from the whole rock of "A-Flow" (1.19 +/- 0.18 Ma). Most
interesting is the olivine in QU-16, which of all the analyses has
the lowest 40K (0.302 ppm), but has the highest 40Ar* (3.65 x
10-4ppm).

Figure 2. K-Ar plot for basalts of Toroweap Dam. If the lava dam has
an "age" of 1.2 Ma, the three QU-16 mineral concentrates should plot
as a line on the 1.2 Ma reference isochron with whole rock sample
"A-FLOW" (arrows indicate where each mineral concentrate should
plot). Instead the mineral concentrates plot significantly above the
1.2 Ma reference isochron, arguing that the lava dam contains
significant "excess radiogenic argon." Can any basalt sample from
the Toroweap Dam be assumed to be free of "excess radiogenic argon?"
If "A-Flow" is actually 1.19 +/- 0.18 Ma, then the mineral
concentrates from QU-16 should each lie on the line in Figure 2
describing an isochron through "A-Flow". The new data do not lie on
that line, but significantly above that line. Why does the basalt of
Toroweap Dam give discordant K-Ar "ages"? There must be "excess
argon" in the olivine of QU-16. Are we sure there is not "excess
argon" in the olivine in "A-Flow" sampled and analyzed as a whole
rock by McKee, Hamblin and Damon [12]? Because many basalts of Grand
Canyon have been shown to contain "excess argon" (e.g., admission by
Hamlin [5, p. 199]), we can ask a more important general question.
Has any Grand Canyon lava dam been demonstrated not to contain
"excess argon"?

The ages of the remnants and dams were deciphered by Hamblin [6]
using both the relative dating method of juxtaposition and the
"absolute ages" determined by K-Ar dating. However, the K-Ar dates
in many cases do not match the relative sequence worked out by
juxtaposition. This may be why most have been discarded after K-Ar
analysis as containing "excess argon". The results of Hamblins work
concerning the relative sequence of development for his 13 dams,
along with other important details, are listed in Table 2.
Table 2. Characteristics of Lava Dams of the western Grand Canyon
(after Hamblin [6]).

Dam Elevation (m) Height
(m) K-Ar Age
(Ma) Number of Flows Dam Length
(km) Lake Length
(km) Water Fill TimeSediment Fill Time
Prospect12006991.83?51823 yr3018 yr
Lava Butte1050560?Several????
Toroweap9274241.25162832.6 yr345 yr
Whitmore7502700.9940+29173240 days88 yr
Ponderosa8403390.611192021.5 yr163 yr
Buried Canyon7442550.898?173231 days87 yr
Esplanade780288?6-813174287 days92 yr
"D" Dam6891910.5840?12387 days31 yr
Lava Falls678180?13512386 days30 yr
Black Ledge6101110.551138+8517 days7 yr
Layered Diabase581890.622022678 days3 yr
Massive Diabase548680.44116645 days1.4 yr
Gray Ledge 544610.78121592 days0.9 yr

The tens of thousands of years Hamblin [6] has interpreted for each
of the 13 dams to form and then erode are seemingly impossible to
reconcile within the several thousands of years of the post-Flood
period. However, several geologic relationships indicate that the
dams actually formed rapidly and failed catastrophically within a
period of less than several hundred years. Furthermore, it is also
evident that several of the 13 dams coexisted, as previously
interpreted by Maxson [10]. We shall highlight these important
conclusions in the following sections by addressing: (1) duration of
dam formation (the amount of time required for each of the
individual dams to form); (2) duration of the dams (the amount of
time each dam was in existence after formation); and (3) the
temporal relationship of dams (the amount of time that transpired
between erosion of one dam and the formation of the next dam).

DURATION OF DAM FORMATION

Hamblin [6] estimated that the total volume of all 13 lava dams was
near 25 km3. The flows are composed of olivine basalt, nearly
identical to those expelled during the highly fluid, late Cenozoic
eruptions of the western United States and other regions of the
world. Fissure eruptions of the Columbia River Basalt resulted on
occasion in the expulsion of hundreds and even thousands of cubic
kilometers of lava in individual flow events [16]. During the
historic Lakagigar eruption of June 8, 1783 in Iceland, a total
volume of approximately 12.2 km3 of olivine basalt lava was expelled
over a period as short as eight months [15]. This eruption resulted
in a complex sequence of thin vertically stacked lava flows very
similar to flows seen in the Uinkaret Volcanic Field.

The single flow lava dams of the western Grand Canyon (refer to
Table 2) could, therefore, have formed within periods as short as
several hours or days. The most extraordinary example is Black Ledge
Dam, which consists of a solitary flow up to 111 m thick and over
138 kilometers long. The Black Ledge lava must have been fast
flowing in order to spread over such a long distance. The
appreciable thickness of the flow probably resulted from damming
along the front edge of the flow as it cooled and hardened. Three
other single flow dams (Lava Falls, Massive Diabase and Gray Ledge)
have been identified. Thickness are from 61 m to 180 m and lengths
are between 16 km to 35 km. Obviously these dams also could have
formed over a very short period of time.

Five dams (Prospect, Toroweap, Ponderosa, Buried Canyon and
Esplanade) where formed by as few as 3 to 8 flows. Most of these
flows are near 100 m in thickness. Prospect Dam consists of three
major flows ranging from 180 to 250 meters thick. The main remnant
of Ponderosa Dam contains one major flow over 300 m thick. Esplanade
Dam actually contains laminated tephra that passes laterally into at
least three lava flow units. This shows that the tephra was
deposited contemporaneously and at near the same rate of the
adjacent flows. The multiple flow dams would have taken longer to
form than the single flow dams, but could have still formed within a
very short period of several months, as demonstrated by the
development of stacked multiple flows in the Lakagigar eruption.
The remaining four dams (Lava Butte, Whitmore, D, and Layered
Diabase) are composed of numerous thin flows from 10 to 40 in
number. These dams probably took the longest time to form. However,
the total time required could have been still very short, probably
as short as several years. Only a short amount of time (the time
required for the upper surface of a flow to cool) is necessary
before a subsequent flow covers the previous flow and creates a
bedding plane between them.

Many of the dam remnants show evidence of erosion between flows, and
also contain interstratified and capping gravel beds. Remnants of
Whitmore Dam along the south wall of the inner gorge contain several
interstratified gravel beds. Although many of the gravel beds lie on
top of flows that exhibit little if any undulatory relief, areas of
moderate scouring indicate erosion did occur. Similar patterns of
interbedded gravels and moderate scouring are found in many of the
other dam remnants, including Prospect Dam and Esplanade Dam. The
main remnant of Buried Canyon Dam is capped with a massive
stratified unit of coarse gravel 60 m thick and contains blocks up
to 1 m in size. Remnants of Gray Ledge Dam are overlain with very
coarse cross-bedded gravel deposits up to 45 m thick and contain
clasts as large as 15 m.

Erosion and deposition are typically used as a uniformitarian
indicator of the passage of a significant amount of time. Therefore,
based on this interpretation, the dams would have taken at least
several hundreds of years, if not thousands to build-up to account
for such erosion and deposition within the dam structures. However,
it is peculiar that thick gravel deposits are found at all within
the dam structures, and we contend that this actually is an
indicator for a rapid process of dam erosion and gravel deposition.
The addition of the volcanic flows into the course of the Colorado
River would have raised the stream bed above the previously
established base level. This would mean that the regions occupied by
the dam would have been subjected to an interval of sustained
erosion until the structure of the dam was worn down to the original
base level. The dam structure could have grown only by the addition
of lava, and not by gravel from stream bedload accumulation. The
stream bed across the dam would have been relatively clean of
gravel, except for relatively small quantities of gravel material in
transport. Thick accumulations of gravel could not have occurred
under normal stream flow conditions.

Clearly, the only process that could account for both the evidence
of erosion, and, the accumulation of thick gravels, would be
periodic catastrophic flooding. During the initial stages of the
flooding episode, erosion of the dam would have been taking place by
flood bedload scouring and cavitation. During the waning stages of
the flood, the sediment load would have dropped out and accumulated
on top of the dam structure, where it then could have been covered
by subsequent lava flows. Rogers and Pyles [13] have suggested that
many of the gravels are the result of high energy/flow breachment or
catastrophic breakout of a dam crest. The coarse cross-bedded gravel
deposit with blocks of up 15 m seen on Gray Ledge flows was clearly
formed by high energy water flow, probably resulting from a dam
breachment event.

DURATION OF DAMS

The best test to determine how long an ancient dam was in existence
is to ascertain the degree to which the lake behind the dam was
filled with sediment. The sediment that a river normally carries
along its coarse will be caught and deposited within the lake
created behind the dammed river. The length of time required for
siltation can be determined if both the volume of the lake and the
sediment transport load of the river are known. The larger the lake,
the longer it will take for the sediment to fill completely that
lake. This test can only be used to place a minimum number of years
for dam longevity, because once the dam is completely silted-in, the
sediment that the river is carrying will then be transported over
the dam. The siltation time required for each of the lakes formed
behind the 13 dams has been calculated by Hamblin [6] and is based
on the sediment load carried by the modern Colorado River into Lake
Mead (refer to Table 1).

Recent surficial deposits related to fluvial-type processes are
relatively sparse within the Grand Canyon. The Geologic Map of the
Eastern Part of the Grand Canyon (1996) identifies two main types of
surficial deposits; river gravels and alluvium. The river gravels
are limited to very recent deposition along the banks of the
Colorado River. The alluvium occurs in isolated outcrops primarily
within the broad valley floors of Nankoweap Creek, Kwagunt Valley,
Sixtymile Creek and Chuar Valley, and is found on terraces at
elevations up to 1500 m (645 m above river level). Remnants of a
thin gravel and boulder deltas are found on terraces at 930 m
elevation on both sides of the Colorado River downstream of Comanche
Creek (miles 67 to 73) [9]. This was probably a temporary delta into
the lake behind the Toroweap Dam. Other relatively large bodies of
surficial-type alluvial deposits are found within Havasu Canyon, at
Lees Ferry, and at several locations in the Lake Powell region.
Hamblin [6] believed that this alluvium was derived from deposition
within the larger Pleistocene lava-dam lakes. An extraordinary
deficiency of lake sediments exists in the canyon of the Little
Colorado River. Apart from these few areas, other significant
deposits of supposed lake deposits are peculiarly absent.
The alluvium (lake sediments) in the eastern Grand Canyon consists
of several small to large gravel deposits located mostly on the west
(left) side of the Colorado River. The larger deposits consist of
four outcrops within the upper basins of Nankoweap Creek, Kwagunt
Valley, Sixtymile Creek and Chuar Valley (refer to Figure 1). These
outcrops range in size from 2 km2 to 5 km2 and are up to several
tens of meters thick, extending up-basin to elevations ranging from
1285 m to 1500 m. These elevations indicate that the gravel deposits
are most likely related to Prospect Lake. Local uplift across one or
several of the normal faults of the Grand Canyon, sometime after
failure of Prospect Dam, has probably raised these deposits above
the 1200 m level of Prospect Lake.

Typical gravels contain clasts derived locally from each particular
depositional basin. Therefore, most deposits are the result of
gravel deltas that built outward into the main lake body, and are
not derived from material transported down the Colorado River.
Elston [4] believed that they may record aggradation by flash
flooding. These gravels probably once extended all the way down to
the Colorado River, where similar small isolated gravel deposits
occur. One small outcrop, located where Nankoweap Creek enters the
Colorado River, is overlain by silty alluvium material and underlain
by gravel which contains exotic clasts derived well upstream of the
Colorado River. Numerous other similar small isolated deposits occur
downstream all the way to Big Bend (mile 75). West of Big Bend these
types of alluvial gravels are not found. The lower gravel units
containing exotic clasts may represent the initial lake deposits
transported down the Colorado River into Prospect Lake.

The up-basin gravels are overlain along their edges by several small
to very large units of talus and landslide debris. These debris
deposits are not known to underlie the gravels in any significant
quantities. The onlapping relationship of the talus and landslide
debris indicates that mass wasting was a post-lake event and may
have resulted from slope instability caused by rapid lake drawdown.
The next large lake sediment deposit occurs within Havasu Canyon.
The main unit consists of a long thin deposit extending 8 km up
Havasu Canyon from Beaver Falls to the Havasupai Indian village.
Smaller isolated outcrops occur both downstream and upstream of the
main deposit. The sediments are composed primarily of silt and fine
sand with interbeds of travertine. Travertine has also armored the
surfaces of the deposits in many areas, particularly along the
course of Havasu Creek. The main deposit reaches a high elevation at
960 m, with small isolated outcrops preserved on the upper canyon
walls at as high as 1032 m. Hamblin [6] believed that these deposits
may include material from several lava-dam lakes, the highest from
Prospect or Lava Butte Lake. The main deposit at 960 m may be from
Toroweap Lake. Hamblin stated that the sediment contains thin
horizontal laminae similar to lake deposits in Lake Mead and Lake
Bonneville. However, the sediments also contain medium- to
micro-scale cross-bedding, showing that they were also influenced by
current flow. This suggests that deposition may have occurred down
Havasu Canyon as an aggrading delta, and not up canyon from material
derived from down-river transport of the Colorado River. Therefore,
the deposits at Havasu Canyon are an isolated, localized unit and
not the result of the complete infilling of a large lava-dam lake.
A sequence of gravel, sand and silt occurs just west of Lees Ferry,
near the confluence of the Paria and Colorado Rivers. This deposit
occurs at and elevation of 1080 m and consists of an upper gravel
unit with clasts over 6 inches in size overlying laminated sand and
silt. Hamblin [6] argues that the sand and silt are indicative of
lake deposits and could not be the result of deposition from the
high energy flow of the Colorado River. However, his explanation
does not address the coarse gravel cap which would have required
swiftly moving currents. We contend that the proximity of this
deposit near the confluence of the Paria is no coincidence and that
they are genetically linked. Swiftly moving currents from flash
floods could have readily transported the entire unit (gravel, silt
and sand) in one or several phases of deposition. Here again, this
material is the result of an aggrading delta fed by material down a
tributary drainage (Paria River) into the lava-dam lake.

The water level of the lava-dam lakes ranged in elevation from a low
of 544 m (61 m above the river) for Gray Ledge Lake to a high of
1200 m (699 m above the river) for Prospect Lake. The majority of
these lakes would have been confined to the thin long channel of the
steep sided inner canyon gorge. The exceptions would have been
Prospect Lake, Lava Butte Lake, and Toroweap Lake. These three lakes
would have been high enough to extend a considerable distance up
many of the side canyons, including Havasu and Kanab Canyons.

Prospect Lake was by far the largest and within the Grand Canyon it
would have covered more than three times the surface area of
Toroweap Lake and extended well up into all of the side canyons
including those of the eastern Grand Canyon, all the way through the
Little Colorado River gorge, and over of the distance up Havasu
and Kanab Canyons. Lake Prospect would have also extended past
present day Lake Powell, approximately 90 m higher then the present
high water elevation of the lake. Below Grand Canyon Village,
Prospect Lake would have completely inundated the Tonto Platform by
over 90 m up to the base of the Redwall Limestone. The sediment fill
time for Prospect Lake (3,000 years) is well below the 10,000-year
duration of Prospect Dam as determined by Hamblin [6], and would
therefore have had more than enough time to fill completely with
sediment under uniformitarian conditions.

Prospect Lake sediments should have been preserved in literally
thousand of locations, ranging from very small to large remnants, if
in fact Prospect Lake was completely sediment filled. Likely areas
of preservation would be within the myriad of protected pockets of
small and large side canyons, and on top of elevated flat-lying
surfaces such as the Tonto Platform where erosion is at a minimum
within the canyon. Appreciable sediment preservation within
protected areas would have also occurred from accumulation in Lava
Butte and Toroweap Lakes. Because the remainder of the lakes were
confined to the steep sided inner gorge, sediment preservation would
have been less likely.

The most interesting characteristic of the lake deposits is that,
nearly without exception, they all occur in low-lying drainages
which are areas of the most active erosion (aside from the main
Colorado River channel). Lake deposits are not found in areas
protected from erosion such as within the thousands of tributary
canyons or, most puzzling, on top of the Tonto Platform such as
below Grand Canyon Village where sediment depths of over 90 m should
have occurred. In fact, the pattern of occurrence of the lake
sediments is exactly opposite of what would be expected. This
pattern indicates that the lake deposits are not remnants left over
from erosion of a sediment-filled lake, but are relatively intact
uneroded depositional units formed by aggrading deltas building
outward from the side canyon tributaries into the main lake body.
This shows that the lava-dam lakes were never completely filled with
sediments, and, therefore, were very short-lived features. We
estimate that this relatively small quantity of lake sediment could
have been deposited in a period of less than 100 years. Multiplying
this value by 13 for the number of total possible lava dams, we
obtain a total of 1300 years for the duration of lava dams blocking
the flow of the Colorado River.

TEMPORAL RELATIONSHIP OF DAMS

Early investigators [10] [11] concluded that only a small number
(one to three) of dams blocked the Colorado River. Maxson [10]
determined that only three lava dams existed, based on the presence
of finely laminated lake-deposited tephra interbedded with volcanic
flows which strongly indicated dam coexistence (found between miles
180.5 and 194.5). Hamblin [6] discounted Maxsons [10]

contemporaneous lava dam theory and proposed that the tephra
developed within temporary lakes formed by landslide dams. Hamblin
offered no substantive evidence for the landslide dams.

McKee and Schenks [11] and Maxsons [10] premise that only a small
number of lava dams once blocked the inner gorge was founded on the
fact that nearly all lava remnants are composed of a similar olivine
basalt. Although they undoubtedly noted the depositional and
textural differences between individual outcrops, the compositional
similarity obviously was paramount in their interpretation.
Hamblins work does suggest strongly that there have been numerous
lava dams within the inner gorge. However, his belief that all 13
dams were separate and non-contemporaneous features is not
necessarily supported by the data. First of all, the finely
laminated tephra observed by Maxson [10] is clear evidence of dam
coexistence. Secondly, many of the remnants are compositionally and
texturally similar, which underscores the potential for error in
Hamblins correlations. Finally, many of the K-Ar dates obtained
from dam remnants are completely ambiguous and yield dates entirely
out of sequence from that determined by the reliable relative dating
method of juxtaposition. Referring to Table 1, the 9 youngest dams
(Ponderosa through Gray Ledge Dams) yield K-Ar dates that are out of
sequence. Our own date determined from a remnant of Toroweap Dam is
older than the oldest date determined for Prospect Dam. We believe
that it is not only possible, but highly probable (based on tephra
deposits and K-Ar dates), that several lava dams coexisted as either
separate dam structures, or even overlapping dam structures.
Figure 3 is based on Hamblins [6] geologic map, and shows the
overlapping relationships between different dam remnants that were
observed in contact in at least one locality. For example, the first
mark in the upper left of the table indicates that one or more
remnant(s) of Gray Ledge Dam overlies a younger remnant(s) of
Massive Diabase Dam. The table shows that there are a total possible
78 different combinations of dam remnant overlap. However, as the
table also shows, only 19 overlap combinations were actually found
by Hamblin. Hamblin questioned two of these overlap relationships.
These are indicated on the table by the queries. Therefore, only 17
dam remnant overlap combinations are known with certainty. Hamblin
worked out his interpretation of the relative sequence of lava dams
from these 17 dam remnant overlap combinations.

Figure 3. Relative Age /Juxtaposition Relationships of Lava Dams.
The upper section of the table shows the contact relationship
between the 6 youngest dams (indicated on the table as:

Juxtaposition Relationship Between 6 Younger Dams - Gray Ledge
through D-Dam). Out of a total of 15 possible overlap combinations,
there are 8 (53%) found for the younger dam remnants. This is a high
percentage and indicates that the relative sequence for the younger
dams has a high degree of reliability. The lower section of the
table shows the overlap relationship for the older dams
(Juxtaposition Relationships Between 7 Older Dams - Buried Canyon
through Prospect). Only 2 overlap contacts out of a total possible
21 combinations (10%) are found in the inner gorge. This is a very
low percentage, and the only relative sequence that can be
determined from these two contacts is that Esplanade Dam is older
than Ponderosa Dam, which is older than Prospect Dam. Therefore, the
relative ages of Buried Canyon, Whitmore, Toroweap and Lava Butte
Dams cannot be worked out amongst these older dams based on
juxtaposition. Therefore, it is possible that these four dams could
have been part of a one large single dam complex, or any other
combination of one or more of these four dam units.

OTHER EVIDENCES FOR CATASTROPHIC DAM FAILURE

Slope Failures Upstream of Lava Dams

The majority of the slopes of the Grand Canyon are devoid of a
notable build-up of talus from mass wastage or landsliding (slope
failures). This general absence of talus deposits is an indicator of
the long term stability of the Grand Canyon slopes. Several large
deposits of talus do occur and are primarily isolated at two
localities. The first location is at Surprise Valley between miles
134-139, and the second is the eastern Grand Canyon in the same
areas of the previously described lake deposits. Only a few mappable
talus deposits are found in the region between these two localities.

The Surprise Valley landslide, which is the largest slope failure in
the Grand Canyon, stretches along the Colorado River for over 8 km
and is over 2 km wide. It is estimated that the slide has a volume
of over 5.5 billion cubic yards.

The slope failures in the eastern Grand Canyon, although much
smaller then the Surprise Valley landslide, are also enormous in
dimension. The largest occurs along the south wall of Chuar Valley,
and is 5 km long and up to 1 km wide. Other large slope failures
occur in Unkar Creek, Kwagunt Valley, and Nankoweap Creek.
Rogers and Pyles [13] assert that water saturation from the
Pleistocene lava-dam lakes was the instrumental factor in the
failure of these large slope areas. Although rapid drawdown of the
lake waters was not necessary for slope failure to occur, it would
have facilitated failure if drawdown occurred prior to complete
slope saturation. The failure would result from what Rogers and
Pyles [13] describe as the development of large hydrostatic forces
that act on the free face of a slope as the water tries to
reestablish equilibrium conditions after a sudden lowering of the
water level by dam failure.

The slope failure talus is almost without exception always overlying
the lacustrine deposits where they occur together. In relation to
this, Elston [4] makes the following statement: " The relations thus
seem to indicate that gravel had accumulated along the course of the
river prior to the episode of catastrophic landsliding, and that it
was a time that the Colorado River was not actively removing
detritus from the area. The pre-landsliding episode of aggradation
thus appears to parallel the episode of aggradation seen in the
eastern Grand Canyon, and landsliding can be inferred to have
occurred during the episode of aggradation." This relationship,
therefore, shows that landsliding occurred only after deposition of
the isolated lake deposits and that it is related to rapid lake
drawdown.

Inner Gorge Widening from Flooding

The inner gorge of canyon widens noticeably at mile 181 and again at
mile187.5. The widening at mile 181 is directly downstream of the
larger and older dams (Prospect, Toroweap, Ponderosa, Lava Butte).
The widening at mile 187.5 is also downstream of these four dams, as
well as the Buried Canyon, Whitmore, and Esplanade Dams. The
widening can be easily explained by catastrophic dam failure and
subsequent flooding.

Near mile 183, a large side canyon on the south side of the inner
gorge opens along an upstream alignment at the first bend in the
river downstream of the older dams. This upstream alignment is
anomalous to the normal alignment of side canyons, which is
typically perpendicular to the inner gorge. The upstream side canyon
alignment is probably the result of flood waters impinging upon the
outer inner gorge wall of the river bend, causing erosion and
formation of the side canyon.

MECHANISM OF CATASTROPHIC DAM FAILURE

Natural dams are typically prone to catastrophic failure by
overtopping. Costa [3] gives two examples of historical breakouts
(1982 in Mexico and 1912 in Alaska) from failure of volcanic dams.
In both of these cases, the dams failed within a year of formation.
The flood from failure of the Alaskan volcanic dam caused scouring
of 1 to 2 m and transported coarse gravel with clasts up to 50 cm
diameter over a 20 km distance.

Catastrophic overtopping or breachment of the lava dams was probably
caused by movement on the Toroweap and Hurricane Faults. Movement
along these faults could have caused both mechanical fracturing of
the dam structures leading to failure, and lake seiches resulting in
dam overtopping. The main remnant of Toroweap Dam shows a decreasing
amount of up-section fault offset across the Toroweap Fault, showing
that the fault was active during the formation of Toroweap Dam. In
fact, both the Toroweap and Hurricane Faults are probably still
active today [6, p. 4].

CONCLUSIONS

Several important geologic features, which have been previously
overlooked, give strong indication that the Pleistocene lava dams of
the western Grand Canyon formed rapidly and were destroyed
catastrophically within several tens to hundreds of years after
formation. We believe that the entire span of time from the
formation of the first dam to the destruction of the last dam could
have transpired over a time-frame of less than 2000 years. We
consider our time estimate to be generous, leaving open the
probability that the total time-frame could have been considerably
less.

It is undisputed, by even uniformitarian geologists, that the
several single flow lava dams formed in a length of time as little
as several hours to days. The larger multiple flow dams (consisting
of 3 to over 40 flows) are commonly stacked one atop the other with
no signs of significant erosion. Although it is clear that in many
instances interflow erosion has occurred, we have shown that the
presence of interflow gravels actually indicates catastrophic
flooding, rapid erosion, and deposition, and, therefore, does not
require us to accommodate hundreds to thousands of years for these
erosional features. Catastrophic flooding is clearly represented by
the coarse cross-bedded gravel on top of Gray Ledge remnants.
The most convincing evidence that the dams where short-lived
structures is the presence of relatively small isolated
depositionally-intact aggraded delta deposits within tributary
drainages of the eastern and central Grand Canyon. The fact that
these relatively uneroded deposits occur within the most active
erosive areas, and the absence of lake deposits on the least erosive
areas (Tonto Platform and protected side canyons), reveals that the
larger lava-dam lakes were not in existence long enough to allow for
complete sediment infilling. The small quantity of delta deposits
that are present could have accumulated easily in less than one
hundred years.

Hamblin [6] believes that 13 separate lava dams once blocked the
inner gorge. The relative age of the 7 older dams were determined by
only two overlap relationships. This allows for the possibility that
several of these dams may have coexisted as a complex mega-dam
structure . The presence of tephra deposits within several dam
remnants is hard evidence that several of the dams coexisted.
K-Ar dates for many of the lava dams are out of sequence from that
determined by juxtaposition. These essentially "impossible" dates
show the difficulty in assessing the sequence of the dam remnants,
and reveals the possibility that many of the correlations proposed
by Hamblin may be in error. Furthermore, a sample of Toroweap Dam
retrieved and dated in this study yielded dates of 3.1, 3.4 and 20.7
Ma, which are significantly older then the date (1.8 Ma) of the
oldest dam (Prospect) determined in Hamblins study. Either
Hamblins dates should be much older or the samples of Toroweap dam
contain excess argon. In any case, the K-Ar dates obtained in this
and Hamblin studies reveal the inherent problems of this dating
method, casting doubt on the standard interpretation of 1.8 Ma for
the Pleistocene Epoch.

The presence of lava-dam remnants near the present level of the
Colorado River reveals that the canyon has undergone only negligible
deepening since the time the dams originally formed. Furthermore,
the normal flow of the Colorado River has not appreciably widened
the inner gorge. Under a uniformitarian interpretation, this means
that the Grand Canyon has not undergone appreciable erosion at least
for the 1.8 million year period of the Pleistocene. A better
interpretation [1] would be that the Grand Canyon is a relic
flood-formed feature, and, likewise, that the lava dams were
short-lived, catastrophically formed and eroded features.

REFERENCES

[1] Austin, S. A., How Was Grand Canyon Eroded?, Grand Canyon:
Monument to Catastrophe, S. A. Austin, Editor, 1994, Institute for
Creation Research, Santee, CA, pp. 83-110.
[2] Billingsley, G.H., and Huntoon, P.W., Geologic Map of Vulcans
Throne and Vicinity, Western Grand Canyon, Arizona, 1983, Grand
Canyon Natural History Association, Grand Canyon, Arizona, one
sheet, scale 1:48,000.
[3] Costa, J. E., Floods from Dam Failures, Flood Geomorphology,
V. R. Baker, et al, Editors, 1988, John Wiley & Sons, New York,
pp. 439-463.
[4] Elston, D. P., Pre-Pleistocene (?) Deposit of Aggradation,
Lees Ferry to Western Grand Canyon, Arizona, Geology of Grand
Canyon, Northern Arizona, 28th International Geological Congress,
D. P. Elston, et al, Editors, 1989, American Geophysical Union,
Washington, D.C., pp. 175-185.
[5] Hamblin, W. K., Pleistocene Volcanic Rocks of the Western
Grand Canyon, Arizona, Geology of the Grand Canyon, Northern
Arizona, 28th International Geological Congress, D.P. Elston, et
al, Editors, 1989, American Geophysical Union, Washington D.C.,
pp. 190-204.
[6] Hamblin, K. W., Late Cenozoic Lava Dams in the Western Grand
Canyon, Geological Society of America Memoir 183 (1994), 139 p.
[7] Hamblin, W. K., and Hamblin, L., Fire and Water: The Making of
the Grand Canyon, Natural History 106 (1997), pp. 35-40.
[8] Koons, D. E., Geology of the Uinkaret Plateau, Northern
Arizona, Geological Society of America Bulletin 56 (1945), pp.
151-180.
[9] Machette, M. N., and Rosholt, J. N., Quaternary Terraces in
Marble Canyon and Eastern Grand Canyon, Arizona, Geology of Grand
Canyon, Northern Arizona, 28th International Geological Congress,
D. P. Elston, et al, Editors, 1989, American Geophysical Union,
Washington, D.C., pp. 205-211.
[10] Maxson, J. H., Lava Flows in the Grand Canyon of the Colorado
River, Arizona, Geological Society of America Bulletin 61 (1949),
pp. 9-16.
[11] McKee, E. D., & Schenk, E. T., The Lower Canyon Lavas and
Related Features at Toroweap in Grand Canyon, Journal of
Geomorphology 5 (1942), pp. 245-273.
[12] McKee, E.D., Hamblin, W.K., and Damon, P.E., K-Ar Age of Lava
Dam in Grand Canyon, Geological Society of America Bulletin 79
(1968), pp. 133-136.
[13] Rogers, J. D., & Pyles, M. R., Evidence of Catastrophic
Erosional Events in the Grand Canyon of the Colorado River,
Arizona, 2nd Conference on Scientific Research in the National
Parks, 1979, 62 p.
[14] Steiger, R. H., and Jager, E., Subcommission on
Geochronology: Convention on the Use of Decay Constants in Geo-
and Cosmochronology, Earth and Planetary Sciences Letters 36
(1977), pp. 359-362.
[15] Thorarinsson, S., The Lakagigar Eruption of 1783, Bulletin
Volcanologique 33 (1969), pp. 910-929.
[16] Tolan, T.L., Reidel, S.P., Beeson, M.H., Anderson, J.L.,
Fecht, K.R., and Swanson, D.A., Revisions to the Estimates of the
Areal Extent and Volume of the Columbia River Basalt Group,
Geological Society of America Special Paper 239 (1989), pp. 1-20.
[17] Young, D, A., The Discovery of Terrestrial History, Portraits
of Creation: Biblical and Scientific Perspectives on the Worlds
Formation, H. J. Van Till, et al, Editors., 1990, William B.
Eerdmans Publishing Co., Grand Rapids, MI, pp. 26-81.
[18] Wenrich, K.J., Billingsley, G.H., and Blackerby, B.A.,
Spatial Migration and Compositional Changes of Miocene-Quaternary
Magmatism in the Western Grand Canyon, Journal of Geophysical
Research 100 (1995), pp. 10,417-10,440.

Additional Resources:

Grand Canyon: Monument to Catastrophe - Steven A. Austin, Editor,
(1994, 288 pp.)
Grand Canyon: Monument to the Flood by Steven A. Austin, Ph.D. (55
min. video)
Impact #307 "Excess Argon": The "Archilles' Heel" of Potassium-Argon
and Argon-Argon "Dating" of Volcanic Rocks by Andrew A. Snelling,
Ph.D. (Jan. 1999)
Impact #224 - Excessively Old "Ages" for Grand Canyon Lava Flows
by Steven A. Austin, Ph.D. (February 1992)
Impact #178 - Grand Canyon Lava Flows: A Survey of Isotopic Dating
Methods by Steven A. Austin, Ph.D. (April 1988)
Catastrophes in Earth History by Steven A. Austin (1984, 318 pp.)
CatastroRef (Catastrophist Geology Reference Database) by Steven A.
Austin (updated from 1994)


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