Temagami Greenstone Belt phases of volcanic activity. These two sequences, known as the Older and Younger volcanic complexes, consist of volcanic rocks ranging in composition from felsic to mafic. The Older Volcanic Complex is composed mainly of felsic lava flows and pyroclastic deposits with smaller amounts of mafic volcanic rocks. It underlies a large portion of northwestern Strathy Township and is penetrated by mafic intrusions, although the Kanichee Intrusion consists of peridotite and pyroxenite, which are ultramafic rocks. Just to the southeast, the Younger Volcanic Complex consists mainly of mafic volcanic rocks that form four geologic formations. The Arsenic Lake Formation is composed
Geology of Guam a foot, which dropped to 0.05 feet further inland. The Guam Waterworks Authority, Guam Environmental Protection Agency, the Air Force and the Navy manage the 180 wells throughout the island. A combination of high-permeability rock, over pumping and overcrowding of wells resulted in 32% of wells (measured in data from the early 1960s through 1997) exceeding a guideline of 250 mg/L chloride concentration. Geology of Guam The geology of Guam formed as a result of mafic, felsic and intermediate composition volcanic rocks erupting below the ocean, building up the base of the island in the Eocene, between 33.9 and 56