Minerals vs. Rocks Common silicate minerals: Olivine- independent tetrahedra joined by Fe or Mg Pyroxene- single chains of linked tetrahedra Amphibole- double chains of linked tetrahedra Micas and Clays- 2-D sheets of linked tetrahedra Quartz- 3-D framework of fully polymerized tetrahedra Feldspar- also a 3-D framework, but Al, Na, Ca, or K can substitute Minerals vs. Rocks Common non-silicate minerals: Calcite- CaCO3 a carbonate Dolomite- CaMg(CO3)2 Apatite- Calcium phosphate (PO4) Halite- NaCl Gypsum- hydrated CaSO4 Rock Types Igneous Ultramafic Mafic (hi Mg-Fe) (hi Mg-Fe) Intermediate Silicic (hi Si-Al) Volcanic Basalt Andesite Rhyolite Plutonic Peridotite Gabbro Diorite Granite Rock Types Igneous Polished slab of granite 10 cm across Thin section of basalt 4 mm across Rock Types Sedimentary Clastic Chemical > 2 mm 0.6 - 2 mm Cobbles, Pebbles Sand Conglomerate Sandstone 0.6 < 0.004 mm 0.004 mm Silt Clay Shale CaCO3 CaMg(CO3)2 SiO2 NaCl, KCl, etc. Limestone Dolostone Chert Evaporites Metamorphic 2) The Earth’s Interior General Geological Principles: 1) Geologic Time Geologic Time Relative dating by superposition, cross-cutting relationships, fossils and evolution Geologic Time Relative dating by superposition, cross-cutting relationships, fossils and evolution Absolute dating by radioactive decay (igneous) 1 ½ ¼ time Isostasy Wood density 0.5 8g 2g 3g 5g 5g 3g 2g Water density 1.0 Each block weighs 2 g 0.5 0.3 0.2 density = 0.1 0.2 Water density 1.0 0.3 0.5 Isostasy Isostasy 3) Plate Tectonics Divergent and Transform Plate Boundaries Continental Rifting Continental Rifting the East African Rift Convergent Plate Boundaries “Andean-type” orogenesis Crust thickens by addition of magma Compression due to plate convergence Convergent Plate Boundaries The Origin of the Himalayas “Himalayan-type” orogenesis Begins as Andean-type “Himalayan-type” orogenesis How do you locate the “suture zone” today? How can you determine the “polarity” of subduction? Slivers of oceanic crust and upper mantle (ophiolites) The “suture zone” is marked by the mélange and become incorporated into the “mélange” in the particularly by the occurrence of ultramafic rocks accretionary wedge of deformed sediments composing the mantle portion of the ocean lithosphere Chain of ultramafic bodies in Vermont indicating a suture zone of the Ordovician Taconic Orogeny. The ultramafics mark a closed oceanic basin between North American rocks and an accreted island arc terrane. From Chidester, (1968) in Zen et al., Studies in Appalachian Geology, Northern and Maritime. Wiley Interscience. Appalachian History Can “accrete” island arc terranes as well as continents Accreted Terranes of the Western Cordillera Hot Spots The Plate Tectonic Regime of the Western USA Earthquakes and Plate Tectonics General Geological Principles: 4) The Rock Cycle Plate Tectonics and the Rock Cycle Examples of Other Cycles: the Hydrologic Cycle Examples of Other Cycles: the Carbon Cycle Population Population Population Impacts: Resources Waste Disposal Pollution Hazards/Disasters Farmland and Food/Soil Disruption of Natural Systems