Rock of ages

Ancient rocks may foretell the future of Antarctica's glaciers as the planet warms.

- VERONIKA MEDUNA

Every rock has a story, and some contain long histories of changing landscapes. This summer, a team of geologists from Victoria University of Wellington Te Herenga Waka spent days walking along Antarctica's mountain slopes to collect rocks that had been dropped by glaciers.

"The glaciers are doing a lot of the work for us," says Jamey Stutz, of the university's Antarctic Research Centre. "They are plucking rocks from their bed, incorporating them into their flow and dropping them off when they ultimately melt out, either next to the mountain or out to sea."

Known as "erratics", these rocks represent the geology buried beneath Antarctica's massive ice sheets, but the team's primary interest is in deciphering the story about how glaciers change shape as they flow from the continent's interior. For this, the team is hunting for "perchies" - rocks that are perched on the side of mountains in such a delicate position that only glaciers could have deposited them there. Essentially, they are marker stones, tracing how far up the mountain a glacier once reached.