IT
IS ALWAYS IN SEASON FOR OLD MEN TO LEARN
Aeschylus
The last five years have provided an amazing
learning experience for me since the Civil War Sesquicentennial has provided a
wealth of written information for amateurs to digest. I have thoroughly enjoyed the opportunities
provided by some very good authors and writers, and dream that my enjoyment
will continue for several years.
Dreams in old guys are part of our personal time machines. Sometimes the machine takes us back and we
experience memories. At other times we
go forward and dream (apologies to Jeremy Irons). One reoccurring dream in my life, other than
forgetting to study for the calculus test, is the first experience in Salt Lake
City. I have written about Utah in
numerous Blog postings since the state played such an important part in my
early adult life. I attended the
University of Utah (1967-1970), spent the 1971-1973 summers as a seasonal Park
Ranger Naturalist (Dinosaur National Monument),
researched my way through two sabbatical leaves (1978 and 1985), completed
about 20 consulting projects in the 1980s (Environmental Impact Studies—Paleontology),
supervised several MS theses on Utah rocks and fossils, and conducted
stratigraphic research for two decades.
So, it seems only normal that I often dream about popping over the
Wasatch Mountains, seeing the Salt Lake Valley with the Lake in the distance,
and wondering if this was the best idea for a small town kid with a new small
town bride.
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Salt harvesting
machine, Solvay Process Company, Salduro, Great Salt Lake Desert. Utah. July
26, 1925. Photo US Geological Survey,
Dept. of Interior.
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At any rate, one of the first trips to explore the
valley was an outing to the Great Salt Lake on the western edge of the City. Like most other tourists to the Lake we were curious
to see if our bodies could really float in the salty water. So off we went on an early free weekend. To put it mildly, the lake was sort of a
disappointment. First of all, the
shoreline of the Lake had a terrible smell.
I later found out that cynobacteria and algae live in this hypersaline
environment and their decaying products produce hydrogen sulfide. In addition, brines flies and brine shrimp
(including their pupae) die and also decay in this low-oxygen shallow water—and
smell. In addition, potential swimmers must
plod through the smelly mud and active brine flies to reach the water. You can float in the water but
immediately after leaving the Lake floaters (you really cannot swim) must find
a shower and rid oneself of the salty effluent crusting on your body.
The Great Salt Lake is sort of a leftover of
Pleistocene Lake Bonneville. The history
of this large (size of ~20,000+ square miles) Pleistocene pluvial lake is quite
complex. Although the “modern" Lake
Bonneville seemed to be present from ~32 ka until ~14.5 ka, pre-Bonneville lakes
occupied the basin as far back as maybe 700 ka.
The “modern” Lake Bonneville begin to disappear as it flooded through an
area called Red Rock Pass in southern Idaho somewhere near 14.5 ka. Great Salt Lake, Utah Lake near Provo (which
is connected to the Great Salt Lake by the Jordan River, and Sevier Lake (near
Delta) are then remnants of this mighty Pleistocene lake.
Lake Bonneville was a fresh water lake as evidenced
by fossils of fish discovered in the sediments associated with the lake. And, large mammals inhabited the shoreline
environments. For several years I was
fascinated by fossils associated with Lake Bonneville and preserved in
shoreline sediments (mostly turning up in sand and gravel quarries). I suppose these sediments have preserved the
greatest concentration of Pleistocene musk oxen of any locality in the world. These oxen were not specimens of the living
species (Ovibos) but an extinct form
called Bootherium.
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Pleistocene Musk
Oxen Bootherium bombifrons in Utah
Museum Natural History. Collected from shoreline sand and gravels of Lake Bonneville. For a discussion of the Pleistocene mammalian fauna see Nelson and Madsen (1987). White strip ~52
mm.
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The Great Salt Lake is an endoheric lake since it has inlet streams and
rivers but does not have an outlet. Therefore,
the Lake has a very high salinity, perhaps up to ~27%, a figure much large than
the oceans ~3.5%. So, human bodies (and
other things) are quite buoyant and float in the water in the Great Salt Lake. In addition, the inlet streams are depositing
several tons of new minerals into the lake each year.
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Satellite images of
northern Great Salt Lake supplied by the US Geological Survey showing recent (1987)
high water level and water level in 2013.
The evaporation basin to the west of the lake contains water in 1987 pumped
to the West Desert by pumps installed by the State of Utah. The “RR Causeway” is part of the Lucin Cutoff
(including about a 12 mile lake trestle) built in the early 1900s that bypassed
the Central Pacific Railroad (part of the “Transcontinental Railroad”) that
originally skirted the lake to the north (Promontory Point).
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Great Salt Lake
sits in a very shallow pan (maybe 30-40 feet at its deepest point compared to Lake
Bonneville at near a thousand feet) and varies considerably in surface size due
to rain and snow in the nearby mountains (input), and in the amount of
evaporation (output). Most geologists
talk about an average size of perhaps 1700 square miles. When I arrived in Salt
Lake City (1967) the University geologists were still talking and teaching
about 1963 when the Lake recorded its lowest level and occupied ~950 square
miles. During my 1985 sabbatical leave
city planners were pressing geologists to examine the stratigraphic record and
guesstimate how much larger the expanding Lake would reach. It seems that the city and county building “experts”
were trying to “fool mother nature” and had allowed buildings on flood plains
and low lying shore deposits. In 1988
the Lake reached a recorded high of ~3300 square miles and cost “someone”
millions and millions of dollars. It is
tough to fool the lady.
I find it
fascinating that DeRose and others (2014) have been able to link elevations during
the last 600 years of Great Salt Lake to broader climate change frequencies in
the Great Basin: The modern instrumental
record of the GSL-level (i.e. elevation) change is strongly modulated by
Pacific Ocean coupled ocean/atmospheric oscillations at low frequency, and
therefore reflects the decadal-scale wet/dry cycles that characterize the
region.
Since Great Salt Lake
is situated in an evaporitic basin, minerals associated with the Lake, and those
deposited in the shoreline environments (that fluctuate in width with the rise
and fall of Lake waters), are evaporitic minerals, especially halite, sodium chloride. However, gypsum (hydrated calcium sulfate, CaSO4-2H2O)
precipitated from Lake Bonneville in the geologic past and numerous gypsum dunes
were left behind in the surrounding desert. In addition, gypsum currently precipitates
from waters of the Great Salt Lake mostly as small flakes of selenite (I think)
and not in abundance like halite.
However, at times in some locations the selenite precipitates out in the
form of elongated blobs termed stalagmites and ever rarer cactus shapes.
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Cactus Selenite
collected in Tooele County on the west side of the lake. Width ~12 cm.
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I purchased my cactus
selenite specimen several years ago during a trip to Utah since something about
the mineral just caught my eye. It was
cheap since the seller seemed to be liquidating his/her collection. Evidently it was collected, according to the
label, by Lehigh Minerals out of Bountiful, Utah. A couple of years ago I looked on their web
site (www.lehighminerals.com) and
found the following information: CACTUS SELENITE, NEW FIND, Great Salt Lake,
Tooele County, Utah, 14 x 12.5 x 6.5 cm, Large Cabinet, New
Find, Selenite Crystals with the individual crystals pointed out
with pointed terminations forming a rounded mound of crystals. The
Selenite is Fluorescent and Phosflorescent with a creamy white color. It
is the first time specimens like this have been found in the Great Salt
Lake. These are white to cream and not any brown.
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Close-up photo of
selenite crystals protruding from the mass giving rise to the “appearance” of
cactus spines. Individual crystals
average ~6 mm.
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That made it kind of
exciting—a five buck specimen that represents a new find. Even more exciting is information from www.findingrocks.com: Cactus' Selenite - Location: West
Side of Great Salt Lake¸ Utah. Large Cabinet. Here we have another new and in
my opinion spectacular discovery from Utah's Great Salt Lake. It should be
noted that we returned to this locality in October 2008 and to our dismay the
area had completely changed and these unusual specimens were all gone!!! In all
likelihood our find from 2007 was merely a one time 'fluke' and it would seem
that there is little likelihood of ever finding more!! There are not many of
these unique specimens still available.
REFERENCES
CITED
DeRose, R.J., S.Y. Wang, B.M. Buckley and M.F.
Bekker, 2014, Tree- ring reconstruction of the level of Great Salt Lake, USA:
The Holocene, v. 24, no. 7.
Nelson, M.E., and
J.H. Madsen Jr., 1987, A review of Lake Bonneville shoreline faunas (Late
Pleistocene) of Northern Utah in
Cenozoic Geology of Western Utah eds. R.S.
Kopp and R. E. Cohenour: Utah Geological Association Publication 16.
Unlike most
large lakes the Great Salt Lake is named for what it truly is -- it is great
and salty. It is also notable for other reasons. Viewed from space
it is an unmistakable landmark in the midst of the Rocky Mountains. To
geographers it is America's Dead Sea. To geologists it is the shrunken
remnant of a great Ice Age predecessor. To engineers it is an obstacle to
travel and a menace to the works of man. Those who would profit from it
regard it as a rich liquid mineral deposit. To tourists it is a natural
wonder like Grand Canyon and Yellowstone Park to be viewed and experienced at
least once.
William
Lee Stokes, my dissertation adviser at Utah