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The scientific community estimates the earth is about
4.7 billion years old, and the oldest exposed rocks in Yellowstone National Park are
2.7 billion years old. I will write more about geologic age estimates later. As an
introduction, the jig saw puzzle which scientists have put together at Yellowstone
shows there was a very large magma chamber in the crust, which gradually built up
pressure and temperature, lifting about 600,000 acres (2,400 square km) of the Rocky
Mountains until there was a major volcanic eruption. The giant volcanic flows in the
Snake River Pains of Idaho are related to this and subsequent eruptions from this
magma chamber. After the initial eruption, and the associated release of temperature,
pressure, and volcanic rocks, the central portion of the uplift collapsed, creating the
Yellowstone caldera. The hot springs, geysers, mud pots and the other hydrothermal
phenomena Yellowstone National Park is so famous for are remnants of this large magma
chamber's breach of the Earth's crust. There are still pockets of magma. They heat
water, and the hot water creates the geologic activity at Yellowstone National Park. Yellowstone Lake sits in this caldera.
Looking at the layering of mud in the bottom of a lake is
similar to counting tree rings. These layers are too thin to see with reflection
seismic wavelets. However, the big picture of where sediments have been deposited
can be determined from the high resolution seismic. Using the maps I created in 1974,
I estimate Yellowstone Lake has 225 square km of surface coverage (over 55,000 acres).
Depositing 0.0709 inches of sediment over this entire area, every year for 1,000 years,
deposits in excess of 14 billion cubic feet of sediment. Removing the up to 255 feet
of water in the lake, I calculate approximately 370 billion cubic feet of sediment have been
deposited in the lake since the caldera was formed. Having grown up on the back end
of a shovel, irrigating a farm in Southern Utah, I know first hand this is a lot of
dirt.
To put it in perspective, just north of
Yellowstone Lake the Yellowstone River has cut the Yellowstone Grand
Canyon, which eventually makes its way into the Missouri and
Mississippi Rivers. This "V" shaped canyon is 1,000 feet deep and 24
miles long. Around 4,000 feet of sediment have been eroded across
the top of the "V," along with all of the sediment in the "V" down
to the current river location This one canyon has had over 250
billion cubic feet of sediment removed from it. Going back up river
to the Lake, with the gross assumption of a constant 14 billion cubic
feet of sediment deposited every 1,000 years, means it would take
over 27,000 years to fill up Yellowstone Lake to it's current level
of sedimentation. Between three identified ice ages, the historically
smaller drainage area prior to erosion and the accompanying smaller
sediment supply from smaller drainage areas, the age derived from
this constant rate of sediment fill is too low by a factor of 24, when compared to other methods used to determine geologic age for this area.
Geoscientists have dated the formation of the caldera at 630 thousand
years ago.
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paradoxes