Skip to comments.Drilling Site Yields Oldest Complete Record of Cyclical Climate Change
Posted on 03/09/2009 1:45:48 PM PDT by Notoriously Conservative
By MALCOLM W. BROWNE Published: Tuesday, December 18, 1990
SCIENTISTS have finished drilling the first of a series of deep holes in an ancient New Jersey lake bed, and preliminary analyses of rock extracted from the hole have yielded the oldest complete record of long-term climate changes ever obtained.
Dr. Paul E. Olsen, a leader of the Lamont-Doherty Geological Observatory group conducting the experiment, says core samples from the hole offer some of the best evidence to date that long-term global climate fluctuations are strongly affected by cyclic variations in motions of the Earth, Moon and planets. The scientists hope this information will lead to better understanding of such questions as to why deserts spread during some periods and recede in others...
Analyses of rock from various depths for mineral composition, magnetic properties, fossil types and numbers, pollen and even dinosaur footprints disclose not only the precise age of each sample but reveal strong patterns of climate change, Dr. Olsen said.
Cyclic patterns of climate fluctuation are difficult to sort out because at least four different patterns are intermingled. To discern the separate components of these fluctuations, Dr. Olsen said, required a mathematical technique, Fourier transform analysis, in which subtle variations are revealed by numerical amplification.
"We assume that the varying depth of this lake was directly related to climate," he said, "and we used a suite of indications from the rock samples to deduce changes in lake depth. The deeper the lake was at any given time, the wetter was the climate."
The scientists said their analyses clearly revealed three basic cycles of climate: 20,000 years, 100,000 years and 400,000 years. "We think we have also found evidence of a two-million-year cyle," Dr. Olsen said.
All these cycles had been predicted from the science of celestial mechanics. Long before scientists began to discern details of cycles, the Greek philosopher Plato estimated a "great year" celestial cycle 20,000 to 30,000 terrestrial years long.
The 20,000-year cycle results from the precession of the Earth's axis as the planet's poles swing around in a slow circle. The 100,000-year and 400,000-year cycles, which can be calculated from interacting gravitational influences of Jupiter, Saturn and Venus, involve changes in the eccentricity of Earth's orbit around the Sun. This orbit at times is nearly circular and at other times is an elongated ellipse. A less significant cycle of 41,000 years is caused by interactions between the orbits of Earth and the Moon around each other.
"What we've seen from our core samples is the best confirmation to date of the existence of these cycles," Dr. Olsen said. The results provide information that could not be obtained from the calculations of celestial mechanics alone. Although the motions and gravitational interaction of any two bodies can be calculated exactly, no such precision is possible when three or more bodies interact.
Calculations result in mere approximations, and "when we try to extend calculation backward more than five million years, the results become chaotic and useless," Dr. Olsen said. (Logically applies to models used to calculate global temperature in the future.)
The rock under scrutiny by the Lamont-Doherty group was formed when all the Earth's land area was combined in one supercontinent, called Pangea (pronounced pan-JEE-a) and a tropical climate prevailed. The huge lake that used to cover present-day New Jersey was created by the splitting apart of crustal rock when Pangea began to break up. The scientists believe that close study of alternating dry and moist periods during the 30-million-year interval surveyed by the New Jersey bore holes may help to explain the spread of deserts in such places as Africa's modern-day Sahel region.
One surprise from the drilling project was the discovery that the 100,000-year cycle, which had been thought to result at least partly from changes in the Earth's ice cover, is apparently independent of ice.
The project is sponsored jointly by the National Science Foundation and the United States Geological Survey. The special drill rig provided by the Amoco Production Company completed the first hole in one month.
(emphasis added by NC)
Hm. How about that. I'm too brain addled to come up with an underwater mortgage joke.
... the New Jersey bore holes may help to explain ...
New Jersey’s state motto, always sleeping wit da fishes.
There are strata even older than these NJ ones which record the climatic influence of sunspots (a much shorter cycle than the ones mentioned here).
Where are they located at? I am curious about all things geological.
Here's another deposit of roughly similar age to the NJ one which shows sunspot cycles and other longer-period cycles:
Thanks for the information. Interesting.
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