September 13, 2017
Journeying to Earth’s Interior on a Mountain in British Columbia
Posted by larryohanlon
By Rebecca Fowler
This is the first dispatch from Rebecca Fowler, a science writer documenting the work of Texas A&M University scientists conducting fieldwork at the Atlin ophiolite in British Columbia.
I spent several days last week on the summit of Monarch Mountain in the company of two Texas A&M University geophysicists and one undergraduate. Our task was to gather geophysical data and rock samples that may yield new insights into the structure and properties of Earth’s interior rock.
Monarch Mountain sits in a rare geological landform called an ophiolite. This is where a portion of Earth’s crust and mantle are exposed at the surface due to some unusual tectonic event. Ophiolites are found all over the world; the one we were on is encompasses Monarch Mountain and the remote lakeside town of Atlin, British Columbia, about 110 miles south of the Yukon Territory border.
With support from the National Science Foundation and NASA, the Texas A&M team is investigating peridotite, a mantle rock. They aim to determine how geochemical processes naturally transform peridotite into a different type of stone. During carbonation, or alteration of the rock, the carbon dioxide in rainwater chemically alters peridotite, causing it to become serpentinite. Through further carbonation, the serpentinite becomes soapstone, which can then turn into another type of rock: listvenite.
Documenting these natural systems — the processes of serpentization and the carbonation of peridotite — will help fill in the gaps about how mantle rock reacts with water and carbon dioxide. Scientists can also use this knowledge to answer key scientific questions about the habitability of planetary environments, how microbes that thrive in the deep in the ocean crust, and how mantle rock might be used to lock away excess atmospheric carbon dioxide.
Because mantle rocks are typically out of reach of prying eyes, hands, and rock hammers, scientists use ships and satellites festooned with instruments to learn about the crust and mantle. Ophiolites provide researchers an opportunity to verify these geophysical measurements by collecting the same types of data at the surface that are obtained by remote sensing tools.
Monarch Mountain is an ideal study site for this research project because its summit contains a quarter mile stretch where the exposed mantle formation clearly shows the boundaries between peridotite and serpentinite, and serpentinite and listvenite. And sub-Arctic ophiolites, like the one in Atlin, are ideal for this type of study because surface rocks are still fresh — they don’t erode quite as quickly in high-altitude environments.
Masako Tominaga is the project’s principal investigator. She and the 2017 team, Patrick Fulton, also a Texas A&M geophysicist; Noah Vento, a senior geology and geophysics major; and me, a science writer and occasional field assistant, carried out a second phase of fieldwork in Atlin in the first week of September. (Read more about the Atlin ophiolite and what we got up to during our 2016 expedition.)
During last year’s time in Atlin, Masako identified the outcrop atop Monarch Mountain and designated it this year’s primary field site. This year, we collected rock samples, and gravity and magnetics data from the outcrop. The variations in Earth’s gravity and magnetic fields found in the information we’ve gathered will ultimately help tell the story of some of the dynamic processes happening on our planet.