Lecture 27

Lecture 27 - Observe this region around the Tibetan Plateau...

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Unformatted text preview: Observe this region around the Tibetan Plateau in Observe southern Asia southern Mount Mount Plateau and Plateau Everest Everest Himalaya Himalaya Exaggerated topographic profile of region 11.00.a Controls on Regional Elevation Regions with thick Regions crust are high crust Warm rocks Warm are higher than cool ones ones Regions underlain by Regions less dense crust are high less 11.01.a Ways to Increase Regional Elevation Shorten-thicken crust Add surface material Add magma at depth Heat crust or mantle 11.01.d Ways to Decrease Regional Elevation Structurally thin crust Cool crust Cool or mantle or Erode material 11.01.e Tectonic Setting of Regional Mtn. Belts Subduction zone Continental collision Mantle Mantle upwelling upwelling 11.02.a Observe the location of regions that have high Observe elevations, and think about why they are high elevations, Western North Western America America Alps Zagros Zagros Mountains Mountains Tibetan Tibetan Plateau Plateau 11.02.b1 Andes East African Rift Great Divide Great Range Range Observe what happens as mountain belts erode Early mountain building Erosion and isostatic rebound Erosion and Erosion uplift bring deep rocks to surface rocks 11.02.c Think about what might control the elevation of across Think North America North 11.02.m1 Western North Western America America Rocky Rocky Mountains Mountains Great Plains Great to Mississippi to Appalachian Appalachian Mountains Mountains How Faulting Can Form Mountains Thrust Faulting Normal Faulting 11.03.b Death Death Valley Valley Denali How Folding Can Form Mountains Active Folding 11.03.c Erosion of Erosion previously folded rock layers layers How Differential Erosion Forms Mountains Hard rock layer resists Hard erosion erosion 11.03.d Granite pluton Granite resists erosion resists Resistant Resistant areas or layers outlast erosion of less resistant ones resistant Observe some settings where basins form 11.04.a Ocean Passive margin Continental rift Normal faulting Regional Regional subsidence subsidence Foreland basin Strike-slip faulting Basins can Basins form in high elevations elevations Major Basins in the Lower 48 States 11.04.b1 The Michigan Basin 11.04.m Observe processes Observe c that form basins ni a ce and mountains at O convergent Accretionary Accretionary boundaries boundaries prism prism Fo th ld a ru st nd be lt 11.05.a Continental crust crust d an l re Fo sin ba Uplifted Uplifted mountain belt mountain Continental crust of underthrusted plate Continental crust of Continental overriding plate overriding Fo re ba lan sin d h nc tre g ng ttiin uc uc bd a e bd atte Su p Su pll Faulting in Faulting continent continent When Extension Accompanies Subduction rift i ng Extension in front of arc front Ba sp ck- a rea r c din g Ba ckarc Continental Continental crust crust Lithospheric Lithospheric mantle mantle Asthenosphere Asthenosphere g ng ttiin uc uc bd bd Su Su e e att pa pll 11.06.a1 Extension on Non-Rotating Fault Blocks Normal faults dip in Normal opposite directions opposite Movement along faults forms Movement basins and mountains basins 11.06.c Over time, basins fill Over and mountains erode and Extension on Rotating Fault Blocks Normal faults all dip in Normal the same direction the Corner that is rotated up Corner becomes a mountain becomes 11.06.c Continued faulting tilts units Continued more, extending crust more, Features of Continental Hot Spots Arabian Peninsula Arabian Afar Region, East Africa Ea st Af ric an R ift Region around Region Yellowstone National Park National 11.07.a a ea Se dS d Re Re Afar en of Ad Gulf Montana Yellowstone Idaho in Pla r ive R Nevada e nak nd e S c a in ovin s Ba e Pr g an R Wyoming Utah Observe how continental hot spots evolve Solid mass rises Solid from lower mantle and melts melts Some magma Some escapes to surface escapes Broad domal uplift and Broad rift with 3 arms rift Normal faults Normal form basins form Third arm fails to Third break up continent break Failed arm low Failed so occupied by major rivers major 11.07.b1-4 Rifting along Rifting two arms forms new ocean new Seafloor spreading Seafloor continues (out of view) continues Continental Interiors Continental shield shield Continental Continental platform platform ult Fa Broad basin 11.08.a Cross section Cross across Ohio across Processes that Affect Continental Interiors Tectonic activity Tectonic can cause uplifts and basins and Uplift Dome Fold Fault Fault Global climate change Global or other processes cause sea level to rise and fall and Tectonic activity may Tectonic form faults, folds, domes, and basins domes, 11.08.b Characteristics of Tectonic Terranes Major faults or shear Major zones separate terranes terranes Different fossils or Different rock chemistry rock 11.09.a1 Different Different sequence of rocks on either side of boundary boundary Different tectonic settings for formation of rocks for Observe common settings for the origin of terranes Piece of seafloor Island arc Oceanic island or Oceanic plateau (hot spot) plateau Piece of Piece continent continent 11.09.a Accretionary Accretionary prism prism Must be added (accreted) via subduction, Must collision, or strike-slip faulting collision, Tectonic Terranes of Alaska Purple and Purple green: slices of oceanic crust and accretionary prisms prisms Pink and Pink red: island arcs or magmatic belts belts 11.09.m1 Gray areas: Gray stable North America America Blue Blue areas: parts of North America sliced off and transand ported Yellow areas: rocks Yellow that overlap terranes that Observe this geologic map of North America, noting the Observe distribution of rock ages distribution Precambrian: Precambrian: dark brown and red and Paleozoic: Paleozoic: purple and blue blue Mesozoic: Mesozoic: green green Cenozoic: Cenozoic: yellow and tan tan 11.10.a1 Observe this geologic map of the world, noting the Observe distribution of rock ages distribution 11.10.b1 Observe the type of terranes in California and Nevada 11.10.m1 Present For the next several slides, observe where the For continents are and predict where they were previously continents 11.11.a1 150 m.y. Ago: Gondwana and Laurasia NAM rifted away NAM from Gondwana from Tethys Ocean 11.11.a2 280 m.y. Ago: Supercontinent of Pangaea Tethys between Tethys N and S parts of Pangaea Pangaea Appalachian Mtns. Appalachian from collision of Gondwana and NAM Gondwana 11.11.a3 370 m.y. Ago: Before Pangaea Island arcs Island off Asia (future terranes) terranes) 11.11.a4 NAM yet to collide with NAM main part of Gondwana main 500 m.y Ago: Dispersal of Continents Most continents Most separated and moving apart moving 11.11.a5 600 m.y. Ago: Supercontinent of Rodinia This view is This centered on South Pole South Continents joined in Continents Rodinia, centered over South Pole over 11.11.a6 Geologic History of the Appalachian and Ouachita Mountains Ouachita Mountains Mountains Ap pa lac hi an s ns aiin ntta un ou Mo yM cky ck Ro Ro M ou nt a in s 11.12.a1 Paleozoic Evolution of Eastern N. America 550 m.y. ago 400 m.y. ago Northern Northern collision with terrane terrane Rifting 500 m.y. ago 300 m.y. ago Collision with Gondwana = Appal. Mtns. 11.12.a Paleozoic Evolution of Appalachian Mtns. 600 m.y. ago 550 m.y. ago 450 m.y. ago 400 m.y. ago 300 m.y. ago 11.12.a Geologic Evolution of the Western U.S. Precambrian Precambrian rifting rifting Early Paleozoic passive margin 11.13.a Middle Middle Paleozoic offshore arcs arcs Late Paleozoic Late collisions collisions End of the End Paleozoic (250 m.y. ago) ago) 11.13.a Early to late Mesozoic convergent Early margin (white line = sections) margin Early to Early Middle Mesozoic Mesozoic Late Late Mesozoic Mesozoic 11.13.a Late Mesozoic and Early Cenozoic Laramide Orogeny Middle and Late Cenozoic Crustal Extension 11.13.a Investigation: Where Will Mountains and Basins Form Investigation: in This Region? in Future magmatic belt Passive margin Future thrust belt Hot spot riifftt all r ntta en ne nn nttii Co Co Small piece of continent of Ocean with no Ocean trenches trenches 11.14.a1 Use this perspective and section to show the main Use features likely to be present in the future features 11.14.a ...
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This note was uploaded on 01/24/2011 for the course GEOL 100 taught by Professor Martin during the Fall '08 term at Maryland.

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