WorldWide Drilling Resource® 257 Caroline Street Punxsutawney, PA 15767 800-927-0560 • 814-427-2555 Fax: 814-427-5164 SERVINGTHECONSTRUCTION INDUSTRY Serving the Drilling Industry 48 SEPTEMBER 2020 WorldWide Drilling Resource ® driving less, nitrogen dioxide and sulfur dioxide levels have decreased over China and much of the United States. Future glaciologists will likely notice the decrease in nitrate and sulfate levels in ice cores retrieved in the future. Thompson has led teams of scientists into some of the world’s most remote areas to drill cores of glacier ice. As snow and ice form each year on glaciers around the world, it doesn’t melt, it just accumulates year by year, stacking one year’s snow and ice on top of all the previous years, over thousands of years. The snow and ice trap whatever is in the atmosphere at the time it forms, including chemicals, minerals, and microbes such as bacteria and viruses, in addition to other organic materials like the stems and leaves of plants. Much like the rings of a tree, ice cores act as a time- line of sorts, showing changes in the atmosphere year-by- year. The onset of the Industrial Revolution in the late 1700s, can be identified. The period when humans began adding chemicals such as sulfate and nitrate to the atmos- phere, and adding lead to gasoline, is also evident in ice cores. Incredibly, ice cores also document the passage of the Clean Air Act in 1970, when atmospheric sulfate con- centrations declined. The cores also show the Plague, also known as the Black Death, a pandemic during the mid-1300s. On some glaciers, the ice formed during the years of the Plague contains less lead than ice formed dur- ing preceding years, likely because mining and smelting activities sharply dropped off during that time. Even more interesting, ice cores from different places around the world show similar changes at the same times. For example, ice from the Huascarán in Peru, and ice from the Tibetan Plateau in the Himalayan Mountains, as well as ice from Kilimanjaro in Africa, all show evidence of a drought around 4200 years ago - the same signature of changes in dust, chemicals, and isotope levels, half a world away. Ice Cores cont’d from page 35.