Pole position

NSF supports two years of work on terrestrial magnetic field shifts

By Greg Scheiderer

Ascension Island isn’t exactly a vacation paradise: It is little more than the top of a volcano sticking out of the Atlantic Ocean, halfway between South America and Africa. But Ascension Island is where Puget Sound Professor Mike Valentine and student Andy Caruthers ’01 spent a chunk of their summer vacation.

Valentine, associate professor of geology, was awarded a grant from the National Science Foundation (NSF) to hunt for evidence of variations in the earth’s magnetic field.

"The last big one occurred 780,000 years ago," he explained. "Brief flips occur more frequently than that. The timing of them is fairly irregular; there’s no real pattern to it, at least as far as we can detect. And they take 10,000 years to happen, so it’s not something where you wake up one day and your compass points in the opposite direction."

Permanent records of the magnetic field are left in volcanic rocks. Valentine says it has to do with minerals in lava flows.

"The minerals become magnetized parallel to the earth’s field at the time the lava cools," said Valentine. By taking rock samples and determining the age of the rocks and the direction of the magnetic field within the samples, geologists get a snapshot of the earth’s magnetic field at that place and time.

Geologists call this phenomenon paleosecular variation. They aim to collect data from all over the world to gain greater understanding of the magnetic field and the forces deep within the earth that are causing the changes.

"One of the things that is needed is a global database," said Valentine. "To model what goes on in the interior we need to know how the field is behaving at various points on the surface." Valentine’s study will fill a significant gap in that database.

"There is no other source for data from volcanic rocks out in the middle of the Atlantic," he said, "so Ascension Island is the only place to get samples for this type of study from that part of the world."

He and Caruthers jetted off shortly after final exams to spend a month drilling for rock samples on the remote island. But that was just the beginning. Analysis of the samples will be done over the next two summers. Another student, Amanda Miller ’03, will assist with the tests. This will involve travel to a couple of the country’s top geology labs.

Miller will visit the brand-new geochronology lab at the University of Wisconsin to do argon-argon testing to determine the age of the samples, and to the Scripps Institute in San Diego to determine the strength of the magnetic field in them. The $82,000 NSF grant will cover the cost of travel and testing. Valentine said getting students involved was a key to landing the NSF funding, which is an "RUI" grant for research in undergraduate institutions.

"The whole purpose is to ensure undergraduate participation in research," said Valentine, adding that Puget Sound shares that aim. "The geology department has a long history of requiring student research. We have a senior thesis requirement; students have to do a research project as part of their degree requirements. I think this will be a great opportunity for them to combine that degree requirement with some cutting edge science and to see what life as a scientist is really like."