Jan 18, 2011
Media contact: Anne Russell
Cell: 604-798-3709
Office: 604-795-2826
anne.russell@ufv.ca
Understanding timing of environmental change using grains of sand lifetime’s work for Lian
Next speaker in the UFV University Lecture Series
The poet William Blake mused about seeing all the world in a grain of sand. For University of the Fraser Valley geography professor Dr. Olav Lian and his student research assistants, it’s more a case of seeing how aspects of the physical world have changed over time by analyzing long-buried grains of sand.
As geochronologists, Lian and his associates view time very differently than many of us; they do this by studying the physical environment as it has changed over the millennia.
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| Dr. Olav Lian outside the luminescence lab. |
Lian is the featured speaker at this month’s installment of the University Lecture Series at UFV. He will speak at 4 pm on Wed, Jan 26, in Room B121, on the Abbotsford campus. Admission is free and all are welcome. Lian’s talk is entitled “Understanding the timing and nature of climatically-driven landscape change in western Canada by reading the landscape’s solar birth certificate.”
By understanding how the physical environment has responded to past changes in climate, it may be possible to predict the impact of future change on the stability of our fragile landscape. To help find when these changes happened, and to be able to link them to intervals of past climate change, Lian uses a technique called luminescence dating, which allows one to date when grains of sand buried within a landscape were last exposed to sunlight — or when that landscape was last unstable. In his lecture he will explain the technique and, using examples, show how aspects of our physical environment have changed in the past, with emphasis on change that has occurred over the past 12,000 years. Lian will also explain how his data can help predict how the landscape might change in the future.
“In order to be able to read the natural clocks’ found in the sand grains, one must have an understanding of what’s happening at the level of the atom,” explains Lian. “By understanding this we can date sedimentary landforms that are only decades old, or up to a half-million years old and sometimes more, which is far more than can be done using radiocarbon dating. This is important as climatically driven landscape change is very much in the public awareness right now.”
Working together with their paleoecologist colleagues, who study ancient plant material preserved in landforms in order to reconstruct the nature of past environments, the researchers can find out when the environments in question occurred.
Doing so involves adventurous forays out into the field to collect samples, but also long hours in the near-total darkness of UFV’s Luminescence Dating Laboratory, as they prepare granular sand specimens for analysis, measure their luminescence properties, and run the resulting data through analytical software.
Trained as a physicist, Lian was a protégé of Simon Fraser University physics professor emeritus David Huntley, who, in the mid 1980s, invented a new method of counting electrons trapped within grains of sand in order to determine their age (the amount of time that had passed since the sand grains were last exposed to sunlight).
Now UFV is home to one of the few luminescence dating laboratories in North America, and currently the only Canadian laboratory of its kind west of Ontario. The highly specialized instrument used to measure the trapped electrons is made by Risø National Laboratory in Denmark.
“If you want to do this kind of research and stay in western Canada, you have to come here,” notes Lian.
In essence, the process is about finding and counting tiny electrons that have become trapped in structural defects and impurities that occur within quartz grains (or within other minerals, such as feldspar). These electrons had become freed from their normal places in atoms by exposure to naturally occurring radiation in the environment.
The researchers do this by isolating quartz grains from the bulk sediment sample collected from the landform of interest. The process involves adding acids and other chemicals to the bulk sample to get rid of unwanted minerals and organic material. The separated quartz grains, each grain no more than a fraction of a millimeter across, are then mounted onto the surface of tiny aluminum disks, which are in turn placed in a carousel within the instrument.
“We can’t see the trapped electrons, but we can make them give their identity up by forcing them out of where they are trapped,” explains Lian.
A computer instructs the instrument to turn the carousel to a position within the instrument where intense blue-green light of a specific wavelength is shone on the quartz grains. The blue-green light serves to stimulate or “jiggle” the electrons out of their traps. The freed electrons promptly find themselves at another kind of site in the quartz grain where their excess energy is given off as light of a different colour, ultraviolet in this case. It is this light which is the luminescence that is measured.
“Simply put, the brighter the measured luminescence, the more time has passed since the quartz grains were last exposed to sunlight, and the older the landform from which the grains were collected,” explains Lian.
The instrument is also used to determine exactly how the brightness of the luminescence measured from the sand grains increases with burial time.
“We want to know whether leaving the sand grains buried in a sand dune, for example, for twice as long doubles the intensity of the luminescence measured, or whether the response is more complicated than that,” notes Lian. “To determine this, the instrument turns the carousel so that the disk holding the quartz grains is under a radioactive source (strontium-90). The grains are exposed to the radiation, and then the luminescence is measured as before; this is done for various doses of radiation. Exposing the sand grains to radiation in the instrument essentially makes them ‘older’, thus simulating a long burial time.”
The laboratory’s equipment needs to measure the extremely low intensities of light that the quartz grains emit when the electrons trapped within them are stimulated, without getting overwhelmed by normal room light. Moreover, exposing the quartz grains to normal room light would empty the filled electron traps before they can be measured, thus resetting the “clocks”. That’s why the laboratory’s rooms must remain in almost total darkness when the samples are prepared and the measurements are in progress. Entering the laboratory is like going into Batman’s cave, with a special portal door that prevents external light from shining in. Lian and his student assistants live a bit of a mole’s life, working with only very low-emission lights in their darkened environment.
But while the students put up with cavelike conditions, they also get a chance to do leading-edge research in a university laboratory while still undergraduates – the kind of research that typically would be done only by graduate students at more traditional universities. Indeed, some return to the laboratory as graduate students to continue their research.
“Our students get a sense of being real (and paid) scientists, working side by side with master’s and doctoral students who visit the laboratory from other universities to perform their research, and they often interact with visiting researchers, some of whom they’ve read about in textbooks and research papers. Students also regularly present their research at national and international professional conferences alongside graduate students, faculty members, and government scientists from all over the world” notes Lian. “This not only gives them a chance to showcase their research, but to meet, mingle, and network with leaders in the field of environmental research”.
Some students have won prestigious awards and scholarships for their work in the laboratory. In 2008 Winter Moon, then a BSc Honours student, won UFV’s first Alexander Graham Bell graduate scholarship from the Natural Science and Engineering Research Council (NSERC) of Canada to continue her research in the laboratory, this time as master’s student. In 2010 Justine Cullen won the Geological Society of America’s 2010 Farouk El-Baz student award for her proposed BSc Honours research. Students from all over the world compete for this award, and only two are given each year, usually to a student at the master’s or doctoral level. Cullen is the first undergraduate student to ever receive the award, and the first Canadian. Justine plans to continue her research in the laboratory next September as a master’s student.
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