Geology of the Feather River Where does one start? NERDS 2006 Teresa Kennedy Some Understandings Plate Tectonics (which is different from continental drift) Subduction results in remelted material (magma) which rises because it is less dense to form new crust Plate margins are places of brittle and ductile deformation The past is the key to the present…geologic processes are dynamic Geologic Time Scale Four Major Eras: Precambrian: Age of Algae Paleozoic: Age of Fish Mesozoic: Age of Dinosaurs Cenozoic: Age of Mammals Overview Igneous, metamorphic, and sedimentary rocks Some tilted, some flat-lying Submarine and subaerial rocks Much of the rock record missing due to erosion Fossils Heavy vegetation Glaciations Precambrian ~ 4.5 billion years ago Until 544 million years ago… Feather River area was at the bottom of the ocean No rocks this old are exposed anywhere close to there! Paleozoic 544 million years to 255 million years ago Western margin of North American craton was 600 – 700 miles to the east 20,000 – 30,000 feet of rock deposited in deep ocean Chert (formed from radiolaria) Volcanic ash and breccia from volcanoes caused by subduction to west. Mesozoic 225 million years to 65 million years Deformation: folding and faulting from collision with other crustal pieces Layers tilted up to 60 degrees Metamorphism from igneous plutons rising from subducted magma. Oldest plutons are to the west Cenozoic 65 million years to present Modern volcanic activity related to spreading of Basin and Range Crest of Sierra Nevada is to the west Uplift • Erosion • Change in climate Glaciers • Erosion • Changes in drainage, soils, vegetation