Azura Spagnazzi

This particular glacier lies near the border between Italy and Austria.

Researchers drilled down through more than nine meters of it, then analyzed this ice core's layers, which hold chemical clues about past events.

Azura Spagnazzi is a climatologist at Ca' Foscari University of Venice.

She says this ice record spans 6,000 years.

Layers from medieval times had spikes of lead, copper, and silver.

likely from air pollution created by increased mining of metals.

Ice layers from other periods showed pollution from massive fires, maybe due to land being cleared for farming.

A report on the findings appears in the journal Frontiers in Earth Science.

Nell Greenfield-Boyce, NPR News.