Clair patterson radiometric dating for kids

clair patterson radiometric dating for kids

Read chapter Clair Cameron Patterson: Biographic Memoirs Volume 74 contains the D.C., Brown had met Esper S. Larsen, Jr., who was working on a method for dating zircon in .. The majority report cites the need to reduce lead hazards for urban children; notes that the . The branching ratio of 40K radioactive decay. Clair C. Patterson, a geochemist who made the first accurate The study was based on the fact that radioactive elements like uranium and. Retrieved [supply date of retrieval] from the World Wide Web: Clair Patterson in the laboratory, circa , the year he came to Caltech. His breakthrough . We boys were by three radioactive progenitors of three different isotopes in this.

Whereas terrestrial lead isotope data had been based entirely on galena ore samples, isotopes could finally be measured on ordinary igneous rocks and sediments, greatly expanding the utility of the technique.

While subsequently applying the methodology to ocean sediments, he came to the conclusion that the input of lead into the oceans was much greater than the removal of lead to sediments, because human activities were polluting the environment with unprecedented, possibly dangerous, levels of lead.

Then followed years of study and debate involving him and other investigators and politicians over control of lead in the environment. The National Academies Press. Thus, in addition to measuring the age of the Earth and significantly expanding the field of lead isotope geochemistry, Patterson applied his scientific expertise to create a healthier environment for society. His father, whom he describes as "a contentious intellectual Scot," was a postal worker.

His mother was interested in education and served on the school board. A chemistry set, which she gave him at an early age, seems to have started a lifelong attraction to chemistry. He attended a small high school with fewer than students, and later graduated from Grinnell College with an A. There he met his wife-to-be Lorna McCleary. They moved to the University of Iowa for graduate work, where Pat did an M. After several months there, he decided to enlist in the army, but the draft board rejected him because of his high security rating and sent him back to the University of Chicago.

At Oak Ridge, Patterson worked in the U electromagnetic separation plant and became acquainted with mass spectrometers. After the war it was natural for him to return to the University of Chicago to continue his education. Laurie obtained a position as research infrared spectroscopist at the Illinois Institute of Technology to support him and their family while he pursued his Ph.

Page Share Cite Suggested Citation: Mark Inghram, a mass spectrometer expert in the physics department, also played a critical role in new isotope work that would create new dimensions in geochemistry. The university had created a truly exciting intellectual environment, which probably few, possibly none, of the graduate students recognized at the time.

Harrison Brown had become interested in meteorites, and started a program to measure trace element abundances by the new analytical techniques that were developed during the war years. The meteorite data would serve to define elemental abundances in the solar system, which, among other applications, could be used to develop models for the formation of the elements.

The first project with Edward Goldberg, measuring gallium in iron meteorites by neutron activation, was already well along when Patterson and I came on board. The plan was for Patterson to measure the isotopic composition and concentration of small quantities of lead by developing new mass spectrometric techniques, while I was to measure uranium by alpha counting. I finally also ended up using the mass spectrometer with isotope dilution instead of alpha counting. In part, our projects would attempt to verify several trace element abundances then prevalent in the meteorite literature which appeared and turned out to be erroneous, but Harrison also had the idea that lead isotope data from iron meteorites might reveal the isotopic composition of lead when the solar system first formed.

He reasoned that the uranium concentrations in iron meteorites would probably be negligible compared to lead concentrations, so that the initial lead isotope ratios would be preserved. Patterson started lead measurements in in a very dusty laboratory in Kent Hall, one of the oldest buildings on campus.

In retrospect it was an extremely unfavorable environment for lead work. None of the modern techniques, such as laminar flow filtered air, sub-boiling distillation of liquid reagents, and Teflon containers were available in those days. In spite of those handicaps, Patterson was able to attain processing blanks of circa 0. His dissertation in did not report lead analyses from meteorites; instead it gave lead isotopic compositions for minerals separated from a billion-year-old Precambrian granite.

On a visit to the U. Geological Survey in Washington D. Alpha counting was used as a measure of the uranium and thorium content; lead, which was assumed to be entirely radiogenic produced by the decay of uranium and thoriumwas determined by emission spectroscopy.

Clair Cameron Patterson - Wikipedia

Despite several obvious disadvantages, the method seemed to give reasonable dates on many rocks. Brown saw that the work of Patterson and me would eliminate those problems, so we arranged to study one of Larsen's rocks. We finally obtained lead and uranium data on all of the major, and several of the accessory, minerals from the rock. Particularly important was the highly radiogenic lead found in zircon, which showed that a common accessory mineral in granites could be used for measuring accurate ages.

As it happened, the zircon yielded nearly concordant uranium-lead ages, although that did not turn out later to be true Page Share Cite Suggested Citation: In any case, that promising start opened up a new field of dating for geologists, and has led to hundreds of age determinations on zircon.

In parallel with the lead work, Patterson participated in an experiment to determine the branching ratio for the decay of 40K to 40Ar and 40Ca. Although the decay constant for beta decay to 40Ca was well established, there was much uncertainty in the constant for decay to 40Ar by K electron capture. This led Mark Inghram and Harrison Brown to plan a cooperative study to measure the branching ratio by determining the radiogenic 40Ar and 40Ca in a million-year-old KCl crystal sylvite.

After graduation, Patterson stayed on with Brown at Chicago in a postdoctoral role to continue the quest toward their still unmet meteorite age goal. He obtained much cleaner laboratory facilities in the new Institute for Nuclear Studies building, where he worked on improvement of analytical techniques. However, after a year this was interrupted when Brown accepted a faculty appointment at the California Institute of Technology. Patterson accompanied him there and built facilities that set new standards for low-level lead work.

By he was finally able to carry out the definitive study, using the troilite sulfide phase of the Canyon Diablo iron meteorite to measure the isotopic composition of primordial lead, from which he determined an age for the Earth.

The chemical separation was done at CalTech, and the mass spectrometer measurements were still made at the University of Chicago in Mark Inghram's laboratory. Harrison Brown's suspicion was finally confirmed! The answer turned out to be 4.

Clair Cameron Patterson

Patterson's reactions on being the first person to know the age of the Earth are interesting and worthy of note. He wrote, 1 True scientific discovery renders the brain incapable at such moments of shouting vigorously to the world ''Look at what I've done! Now I will reap the benefits of recognition and wealth. There "we" refers to what Patterson calls "the generations-old community of scientific minds. To him it must have been an exercise in improving the state of the "community of scientific minds.

In the meantime, there have been small changes in the accepted values for the uranium decay constants, improvements in chemical and mass spectrometric techniques, and a better understanding of the physical processes taking place in the early solar system and Earth formation, but these have not substantially changed the age Patterson first gave to us.

Some textbooks have given diagrams showing that the logarithm of the supposed age of the Earth plotted against the year in which the ages appeared approximated a straight line, but Patterson's work has finally capped that trend.

Patterson next focused on dating meteorites directly instead of inferring their ages from the Canyon Diablo troilite initial lead ratios. He did this by measuring lead isotope ratios in two stone meteorites with spherical chondrules chondrites and a second stone without chondrules achon- Page Share Cite Suggested Citation: A colleague, Leon Silver, had recommended the achondrite because of its freshness and evolved petrologic appearance. They also fit the 4. The meteorite work led indirectly to his second major scientific accomplishment.

The new ability to isolate microgram quantities of lead from ordinary rocks and determine its isotopic composition had opened for the first time the path for measuring lead isotopes in common geological samples, such as granites, basalts, and sediments.

That led him to start lead isotope tracer studies as a tool for unraveling the geochemical evolution of the Earth. As part of that project he set out to obtain better data for the isotopic composition of "modern terrestrial lead" by measuring the isotopic composition of lead in ocean sediments. By Tsaihwa J. Chow and Patterson reported the first results in an encyclopedic publication that initiated Patterson's concern with anthropogenic lead pollution, which was to occupy much of his attention for the remainder of his scientific career.

The isotope data revealed interesting patterns for Atlantic and Pacific Ocean leads that could be related to the differences in the ages and compositions of the landmasses draining into those oceans. However, in studying the balance between input and removal of lead in the oceans, the Page Share Cite Suggested Citation: Thus, the geochemical cycle for lead appeared to be badly out of balance. The authors noted that their calculations were provisional; the analytical data were scarce or of poor precision in many cases, however this was the seminal study that started Patterson's investigations into the lead pollution problem.

The limitations in the analytical data on which many of the conclusions in the paper were based led Patterson to start new investigations to attack the problem. In he published a report with Mitsunobu Tatsumoto showing that deep ocean water contained 3 to 10 times less lead than surface water, the reverse of the trend for most elements e.

This provided new evidence for disturbance in the balance of the natural geochemical cycle for lead by anthropogenic lead input. In the paper entitled "Contaminated and Natural Lead Environments of Man," 2 Patterson made his first attempt to dispel the then prevailing view that industrial lead had increased environmental lead levels by no more than a factor of approximately two over natural levels.

Clair Cameron Patterson | Biographical Memoirs: V | The National Academies Press

He maintained that the belief arose from the poor quality of lead analyses in prehistoric comparison samples in which much of the lead reported was actually due to underestimation of blank contamination. He compiled the amounts of industrial lead entering the environment from gasoline, solder, paint, and pesticides and showed that they involved very substantial quantities of lead compared to the expected natural flux.

He estimated the lead concentration in blood for many Americans to be over times that of the natural level, and within about a factor of two of the accepted limit for symptoms of lead poisoning to occur. He called Patterson's conclusions "rabble rousing. The enclosed manuscript does not constitute basic research and it lies within a field that is outside of my interests.

This is not a welcome activity to a physical scientist whose interests are inclined to basic research. My efforts have been directed to this matter for the greater part of a year with reluctance and to the detriment of research in geochemistry. In the end they have been greeted with derisive and scornful insults from toxicologists, sanitary engineers and public health officials because their traditional views are challenged.

It is a relief to know that this phase of the work is ended and the time will soon come when my participation in this trying situation will stop.

In it he claimed that the California Department of Public Health was not doing all it should to protect the population from the dangers of lead poisoning. His first request drew a polite rejection. A second letter on March 24,had better success, perhaps because of a letter from a high state official.

Uranium-lead dating facts for kids

He had simultaneously started parallel actions at the national level as well. In it he offered to appear before the committee. He was subsequently invited to a hearing held on June 15,in Washington. There Patterson emphasized that most officials failed to understand the difference between "natural" and "normal" lead body burdens, the former based on incorrect data from pre-industrial humans, the latter on averages in modern populations.

In support of that assertion he cited his newer work in Greenland showing the large increases in lead in snow starting with the industrial revolution. He furthermore believed it was wrong for public health agencies to work so closely with lead industries, whom he considered often biased in matters concerning public health. His views drew support from some of the public e.

Kehoe, the highly regarded authority on industrial poisoning. A battle line was drawn that was to last about two decades. By Patterson and his colleagues had completed studies of snow strata from Greenland and Antarctica that showed clearly the increase in atmospheric lead beginning with the industrial revolution in both regions. Modern Greenland snow contained over times the amount of lead in preindustrial snow, with most of the increase occurring over the last years. The effect was about ten times smaller in Antarctic snow, but it was clearly observable.

The job of the team was to measure the concentration and isotopic compositions of the elements inside the zircon. Tilton was to measure the uranium and Patterson, the amount and type of lead.

In doing so, it would be possible to figure out the age of the solar system and, in turn, the Earth from using the same techniques on meteorites. As Patterson and Tilton began their work inPatterson quickly became aware that his lead samples were being contaminated.

They knew the age of the igneous rock from which the zircon came, and Tilton's uranium measurements aligned with what should be in a zircon at that particular age, but Patterson's data always was skewed with too much lead.

Brown was able to receive a grant from the United States Atomic Energy Commission to continue work on dating the Earth, but more importantly, to commission a new mass spectrometer in Pasadena, California at Caltech.

clair patterson radiometric dating for kids

InBrown brought Patterson along with him to Caltech, where Patterson was able to build his own lab from scratch. In it he secured all points of entry for air and other contaminants. Patterson also acid cleaned all apparatuses and even distilled all of his chemicals shipped to him. In essence, he created one of the first clean rooms ever, in order to prevent lead contamination of his data.

He used the mass spectrometer at the Argonne National Laboratory on isolated iron-meteorite lead to collect data on the abundance of lead isotopes. Deriving from the different ages at which the landmasses had drained into the ocean, he was able to show that the amount of anthropogenic lead presently dispersed into the environment was about 80 times the amount being deposited in the ocean sediments previously: The limitations of the analytic procedures led to his use of other approaches.

He found that deep ocean water contained up to 20 times less lead than surface water, [4] in contrast to similar metals such as barium.

That led him to doubt the commonly held view that lead concentrations had grown by only a factor of two over naturally occurring levels.

clair patterson radiometric dating for kids

Patterson returned to the problem of his initial experiment and the contamination he had found in the blanks used for sampling. He determined, through ice-core samples from Greenland taken in and from Antarctica inthat atmospheric lead levels had begun to increase steadily and dangerously soon after tetraethyl lead began to see widespread use in fuel, when it was discovered to reduce engine knock in internal combustion engines.

Patterson subsequently identified that, along with the various other uses of lead in manufacturing, as the cause of the contamination of his samples.

Because of the significant public-health implications of his findings, he devoted the rest of his life to removing as much introduced lead from the environment as possible.