Geology of the Northwest Territories province from dikes and mafic lava flows, overlain by deep ocean turbidite deposits. These rocks are believed to be the remains of oceanic crust that ended up preserved, surrounded on all sides by felsic volcanic rocks and granitoid plutons. In the area of Snofleld Lake in the northern part of the Slave Province, the remains of Archean stromatolites are preserved in a dolomite unit between felsic volcanic and greywacke-mudstone turbidites, some of the earliest evidence of life, forming in the shallows around volcanic islands. Around 1.27 billion years ago in the Proterozoic, a series of major magmatic events affected the
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