Landform Processes Plate Tectonics The Rock Cycle CA’s Geologic History
Extrusive igneous rock: basaltic lava flow, Fossil Falls, Basin & Range
Intrusive igneous rock: granite; outcroppings in Castle Crags
Metamorphic Rock; White-Inyo Mountains; very old rock ( + billion years)
Sedimentary rock; Eagle Rock, Topanga State Park; 25 mya; uplift, folding, faulting have put it at an angle
Older, darker metamorphic rock on top of younger, lighter colored granite that lifted it; Convict Lake, Sierras.
Pre-Cambrian Era 4.6 bill – 570 mya Paleozoic Era 570 mya – 250 mya Mesozoic Era 250 mya – 65 mya Cenozoic Era 65 mya - present
Granite escarpment of eastern Sierras with Alabama Hills in foreground Granite escarpment of eastern Sierras with Alabama Hills in foreground. Uplifted Sierra peaks, downfaulted valleys (Owens, Death) during Cenozoic era.
Granite in Mojave National Preserve Granite in Mojave National Preserve. Plutons exposed after erosion and weathering.
Northern CA: Cascades, Modoc Eastern Sierras, Basin & Range Imperial Valley Sonoma, Clear Lake
Geothermal activity, Modoc Plateau
Shasta Peak
Long Valley Caldera, Mammoth Lakes, man-made Lake Crowley now, erupted 700,000 years ago
Devil’s Postpile, andesitic lava flow, 600,000 years ago, while cooling, cracked into near-perfect six-sided columns.
Weathering Chemical Mechanical Differential weathering
Alabama Hills: differential weathering, igneous rock
Santa Monica Mountains: differential weathering of sedimentary rock
Spheroidal weathering, Topanga State Park
Mechanical, chemical weathering: Alabama Hills
Mass Wasting Soil creep Liquefaction Landslides
Mass Wasting
La Conchita Landslide, 1995 La Conchita Landslide, 2005
Coastal Landforms Marine terraces Sea stacks
Sonoma County coast: sea stacks.
Sea stack isolated by marine terracing.
Marine Terracing
Aeolian Landforms Wind Erosion and Deposition Coastal and Desert Dunes
Death Valley: aeolian ripples, dunes (perpendicular to wind direction)
Glacial Landforms Alpine glaciation Erosional: cirques, horns, aretes, tarns, u-shaped valleys, hanging valleys Depositional: glacial till, moraines
Yosemite, u-shaped valley, alpine glaciation, hanging valley
Glacial lateral moraine: Sierra Nevadas
Alpine glaciation: cirque; Tioga Pass Route 120
Horns, aretes; Lone Pine peak
Horns, glacial polish, Yosemite
Fluvial Geomorphology Erosion & Deposition River Courses Arid Landforms Alluvial Fans Bajadas Playas
Steep, stream-cut canyon, Whipple Mountains
Alluvial fan, Panamint Valley
Bajada