Thursday, July 1, 2010
Sharon Mosher, a geologist and dean of the Jackson School of Geosciences, talks about working in geologic time.
Sharon Mosher explains what she does as a geologist:
“I’m a structural geologist and I tackle tectonic problems,” she says. “I study everything from recent—and my definition of recent is probably not yours—to plate boundaries that are 1.2 billion years old.”
For her, “recent” means five to 10 million years ago.
But, she adds, 1.2 billion years ago is young in the total age of the Earth.
“We go back to having records of events that are 4.5 billion years old on Earth,” Mosher says. “I took a group of 16 students to western Australia once and it was eye opening for me because all of the rocks we saw were older than two billion years old.”
Mosher wanted to be a geologist since she was five years old and the concept of geologic time became natural to her.
“I never found it that difficult,” she says, “maybe it’s because from an early age I taught myself geology and so I got used to the idea.”
She says a geologist does think about time differently.
When a geologist talks about climate change or the extinction of species, those are things that have occurred over and over in Earth’s history over periods of time, she says.
“We’re used to the idea that those things happen and you really have to watch geologists, you have to say, ‘OK, but what about in a human time frame?’ Because very commonly you’ll get an answer and the people listening are thinking in a human time frame whereas the geologist is thinking millions of years. It is different. It really is.”
OK, geologists get geologic time because that’s what they deal with everyday. How do they teach it to beginning geology students?
“It’s actually somewhat difficult,” Mosher says.
“One of the things we do in introductory classes is we have a timeline. In my case, it was a string with orange flags on it,” she says. “You’d get in a big auditorium and you have students come down. One would hold one end and every place there was an orange flag they’d hold and you’d have them start and each one would read their flag.
They’d see that it was quite a while before life planted its flag on the planet.
“What they find is that three-fourths of the auditorium is covered by string before they hit something where there was any life at all,” she says. “Then they’re all crowded together at the end because all these things they’re used to thinking about are all at the very end.”