Alternative Division of Earth: based on mechanical behavior of solid Earth
    lithosphere ("rocky sphere"), includes crusts plus some upper mantle
        lithosphere: outer layer, coldest and therefore strongest rocks, rigid layer
    asthenosphere ("weak sphere"), rest of mantle below lithosphere
        asthenosphere:  inner layer, hottest and weakest rocks, solid but gooey, pliable
    Plate:  a piece of lithosphere; a rigid slab of cold crust and upper mantle
        think: ceramic dinner plate (rigid, large area and small thickness, slablike)
        ex:  Pacific Plate (large), African Plate (medium), Juan de Fuca Plate (small)

Plate Tectonics Rules: tectonics comes from the Greek word tekton, to build/construct
    (1) asthenosphere is heated from below, light asthenosphere rises as solid to surface
    (2) as asthenosphere cools and sinks, plates dragged around on surface of Earth
        plates are moving around on surface of Earth a few inches per year
        can measure speed & direction from satellites, hot spot tracks (see below), etc.
    (3) plates grind past, bump into and pull way from each other, creating geology!
    (4) therefore:  most geology (but not all) happens at plate edges, at plate boundaries

Diverging Plates:  two plates moving apart; plates rifting apart, moving away
    "divergent" or constructive boundary:  new crust being created at divergent boundary
    oceanic rifts/mid ocean ridges:  new plate produced by underwater lava
        Mid-Atlantic rift, East Pacific Rise, Juan de Fuca Ridge, Indian Ocean Ridge, etc.
    continental rifts: separation of continents; East Africa, Basin and Range in Nevada
all rifts:  small shallow earthquakes; lots of magma; high heat flow; basins or rift valleys

Converging Plates: two plates moving towards each other, two plates colliding
    "convergent" boundary:  either destructive (old crust recycled) or collisional
    destructive boundary:  oceanic plate recycled into mantle at subduction zone
            deep trench, large earthquakes, string of volcanoes (volcanic arc)
        1.  oceanic plate subducted under oceanic plate:  island arc/oceanic arc
            ex/  Caribbean arc (Antilles), Aleutian arc, Marianas arc, Scotia arc.
        2.  oceanic plate subducted under continental plate: continental arc
            ex/  Andes, Central America, Cascade volcanoes ("Ring of Fire")
    collisional boundary:  continent-continent collision, large mountain range
        e.g. modern Himalayas and Tibet; ancient Cascades, ancient Appalachians
    NB: mountains  (train wrecks) are not volcanoes  (cone-shaped pile of lava)

Sideways Moving Plates: two plates grinding past each other sideways
    "transform" or "transcurrent" plate boundary:  no plate produced or consumed
        no volcanoes or mountain ranges; but large abundant shallow earthquakes
    large faults (breaks in the lithosphere) with sideways motion
        San Andreas Fault separating North American Plate from Pacific Plate
        Alpine Fault in New Zealand separating Pacific Plate from Australian Plate

Hot spots:  points where blobs of asthenosphere rise up, fixed points in the mantle
    as plate moves over fixed hot spot, a chain of volcanoes or lava flows  is produced
    oceanic hotspots:  e.g. Hawaii, Easter Is.
        chain of volcanoes (seamounts/guyots) on ocean floor
    continental hotspots: ex:  Yellowstone.
        slug track of lava flows extending across Idaho

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