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- CaCO 3 a carbonate Dolomite- CaMg(CO 3 ) 2 Apatite- Calcium phosphate (PO 4 ) Halite- NaCl Gypsum- hydrated CaSO 4

Rock Types l Igneous

Rock Types l Igneous Polished slab of granite 10 cm across Thin section of basalt 4 mm across

Rock Types l Sedimentary l Metamorphic

2) The Earth’s Interior

General Geological Principles: 1) Geologic Time

Geologic Time l Relative dating by superposition, cross-cutting relationships, fossils and evolution

Geologic Time l Relative dating by superposition, cross-cutting relationships, fossils and evolution l Absolute dating by radioactive decay (igneous) # parent atoms time  1½¼

Isostasy Water density 1.0 Wood density g 3 g 5 g 8 g Water density density = 0.1 Each block weighs 2 g

Isostasy

Isostasy

3) Plate Tectonics

Divergent and Transform Plate Boundaries

Continental Rifting

Continental Rifting the East African Rift

Convergent Plate Boundaries

“Andean-type” orogenesis l Crust thickens by addition of magma l 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) become incorporated into the “mélange” in the accretionary wedge of deformed sediments The “suture zone” is marked by the mélange and particularly by the occurrence of ultramafic rocks 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: l Resources l Waste Disposal l Pollution l Hazards/Disasters l Farmland and Food/Soil l Disruption of Natural Systems