Nature’s Graffiti – March 4, 2020
It’s Science Wednesday! Two weeks ago, we visited Horseshoe Island in the Antarctica Peninsula, below the Antarctic Circle. It was discovered and named by the British Graham Land Expedition under John Rymill, who mapped the area by land and from the air in 1936–37. Upon landing, there were signs of what looked like green graffiti on many rocks nearby the old British station, which was used in the 1950s. In fact, this was nature’s graffiti, in the form of a secondary mineral called malachite, a copper carbonate hydroxide Cu2(CO3)(OH)2. Secondary means it’s not an original mineral of the rock…it came along after the rock had already formed. How? Due to volcanic activity in the area, hydrothermal fluids were able to form. Due to tectonic activity and fluid pressure, they were then injected into joints and fissures of the surrounding rock (in this case, granite). The copper in the mix was eventually oxidized when exposed to air and transformed into this brilliant shade of green we see today.