If this poor, unassuming rock is buried, however, cosmogenic radionuclide accumulation will halt. Glaciers are particularly good at blocking cosmic radiation from reaching the bedrock over which they slide and, here in the McMurdo Dry Valleys, we have sampled that exact bedrock that was once covered by overriding glacial ice. We will take these samples back to the U.S. with us and measure itty bitty concentrations of cosmogenic radionuclides that are contained within.<\/p>\n
Sidebar: What\u2019s an \u201citty bitty\u201d concentration? Glad you asked. We are typically measuring element concentrations on the order of millions of atoms. That may sound like a lot, but don\u2019t be fooled! Take a commonly measured cosmogenic radionuclide (and my personal favorite), beryllium (Be). 1 gram of Be contains more than 1 sextillion atoms. That\u2019s more than 1 billion trillion<\/strong> atoms\u2026in just 1 gram of the stuff! That means that the concentrations we measure represent about 0.00000000000000001% of 1 gram<\/strong> of Be!<\/p>\n It\u2019s ok \u2013 it blows my mind, too.<\/p>\n The exposure history of these rocks help us better understand how glaciers have grown and shrunk in the past. In turn, these changes in glacial behavior help us interpret changes in the climate and what the Dry Valleys region may have looked like long before we arrived here.<\/p>\n A common sampling technique is to target large boulders that have been pushed to the glacier\u2019s furthest extent. Unfortunately, many small cirque glaciers in the Dry Valleys do not move such massive rocks. Here, in Dipboye Cirque, upper Wright Valley, we\u2019re testing a new technique on meter-scale boulders.<\/p>\n We use a rock drill to set wedges and shims into the rock surface then we hammer away with a sledge until the rock surface pops loose for us to collect. The technique is adapted from stone masonry \u2013 and has earned me the unfortunate nickname \u201cThe Destroyer\u201d.<\/p>\n Now that we\u2019ve returned to McMurdo, these samples will get packed up and sent on a long journey home via ocean cruiser. After much time in prep at the University of Pennsylvania Cosmogenic Isotope Laboratory, they\u2019ll be sent off for atomic mass spectrometry analysis. All in all, sample collection to data point generation takes ~1 year. In the meantime, I\u2019ll be waiting patiently J<\/p>\n This is The Destroyer, clear.<\/p>\n","protected":false},"excerpt":{"rendered":" Guest blogger: Rachel Valletta, University of Pennsylvania As you\u2019re reading this, invisible cosmic rays are relentlessly bombarding the earth\u2019s surface, smashing into and tearing apart molecules, and creating new radioactive elements. So, that\u2019s weird. This bizarre-o process is how cosmogenic … Continue reading ![\"\"](\"http:\/\/blogs.uml.edu\/antarctica-2015\/wp-content\/uploads\/sites\/36\/2015\/12\/Untitled.png\")
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