Office Hours Tuesday Thursday 11 00am 12 00pm or by appointment GEOL 1001 3 Instructor Dr Tiffany Roberts Room Howe Russell 130 Office E209 Howe Russell Office Phone 225 578 2801 Email tiffanyroberts lsu edu TA Abah Omale Email aomale1 lsu edu Office location 205 Howe Russell Office Hours M W 1 00 2 00pm Exam 4 Chapters 12 14 23 Date 4 23 14 Location Himes Testing Center 3 25 14 Chapter 12 Earth s Internal Structure Important concepts Properties of Earth Internal structure layers How do we know cid 127 Mantle convection cid 127 Magnetic field Earth s Layers Compositional chemical Physical properties rigidity Essential to understanding geologic phenomena How do we know Seismic waves 7 5 miles is deepest drill Earth s diameter 7 900 miles 3 950 mile radius Seismic waves Travel at different speeds Temperature Composition Paths Reflected Refracted waves cid 127 When seismic waves encounter a boundary between materials with different properties such as air and water the energy splits into reflected and refracted cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 When the velocity of seismic waves increases as they pass from one layer into another the waves refract bend toward the boundary separating the cid 127 When the velocity of seismic waves decreases as they pass from one layer into another the waves refract bend away from the boundary separating Seismic waves and mineral physics reveals Earth s internal layering layers them Earth s Layers Lithosphere Asthenosphere Transition zone Upper mantle Lower mantle cid 127 Outer core liquid Inner core solid Earth s Temperature Radioactivity is the source of heat driving mantle convection Any plate movements Heat flow Lithosphere Asthenosphere Transition zone Upper mantle convection Lower mantle convection cid 127 Outer core liquid conduction and convection Inner core solid conduction Upper brittle crust upper mantle Hot weak rock asthenosphere still solid 3 27 14 Chapter 13 Divergent Boundaries Important concepts Continental margins Seafloor bathymetry geologic features cid 127 Mid ocean ridge Formation of ocean basins Destruction of oceanic lithosphere Earth s magnetic field Convection of liquid iron in the outer core creates a magnetic field 1 Earth s rotation causes spiral flow in the iron rich liquid outer core that aligns with the spin axis 2 The electrically charged spiral flow in the outer core generates earth s magnetic field This is similar to how an electromagnet works cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 Mapping the ocean floor 1 Continental shelf 2 Continental slope 3 Continental rise 4 Seamount 5 Abyssal plain 6 Rift valley 7 Abyssal plain 8 Seamount 9 Continental rise 10 Continental slope 11 Continental shelf Margins Passive Margins cid 127 Wide continental shelves cid 127 Geologic activity minimal Active margins Narrow continental shelves cid 127 Geologically active Features of the seafloor Deep ocean trenches Abyssal plains Volcanic islands Seamounts cid 127 Guyots cid 127 Mid ocean ridge MOR cid 127 Ocean ridge cid 127 Offset by transform faults Seafloor spreading Rates topography Slow spreading rates Oceanic crust cid 127 Ophiolite complex layers Pillow basalts Deep sea hydrothermal vents Associated with active margins volcanism cid 127 Mariana trench 11 000m deep avg depth of ocean 4 200m Aprominent central rift valley develops along the ridge crest The topography of the ridge is typically rugged Poorly developed magma chamber Fast spreading rates cid 127 Medial rift valleys do not develop The topography is comparatively smooth cid 127 Well developed magma chamber cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 1 Tensional forces and buoyant uplifting of the heated lithosphere cause the upper crust to be broken along normal faults while lower crust deforms by Birth of an ocean Pangaea began rifting 200 MYA East Africa is currently undergoing a similar process 2 As the crust is pulled apart large slabs of ocean rock sink generating a rift valley 3 Further spreading generates a narrow sea 4 Eventually an expansive ocean basin and ridge system are created ductile stretching Supercontinent cycle cid 127 Mantle plumes Triple junctions Failed rifts Destruction of ocean lithosphere Spontaneous subduction Lithosphere mantle is old cold and dense Subducts at a steep angle Forced subduction Young warm buoyant lithosphere Subducts at a low angle Chapter 14 Mountain Building Important concepts cid 127 Mountain building Convergence and subduction Convergence and collision Faul block mountains Isostasy Mountain Building cid 127 What s a mountain cid 127 Orogenesis cid 127 Mechanism of orogenesis Plate tectonics Convergent boundaries Convergence subduction Subduction zones mountains 4 regions of subduction zones 1 Volcanic arcs 2 Deep ocean trenches 3 Forearc between island arc and subduction 4 Back arc between arc and continental dry land Convergence orogeny Island arc type orogeny A large natural elevation of the earth s surface rising abruptly from the surrounding level Term for processes that collectively produce a mountain belt cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 Volcanic island arc Andean type orogeny Continental island arc Passive continental margin Subduction continental volcanic arc accretionary wedge Batholith formation uplift forearc basin Collisional mountain belts Convergence without subduction created the tallest mountains on earth Tallest peak currently on earth cid 127 Mount Everest 8 848m 29 029f in the Himalayan mountains cid 127 Microcontinents volcanic arcs oceanic plateaus cid 127 Mountains formed by the closure of major oceans Cordilleran type Accreted terranes Accretion and orogenesis Alpine type Himalayas Appalachians Urals Alps Suture Preserves ophiolites Fold and thrust belts Earth s youngest mountains Himalayas 50MYA Earth s oldest mountains Appalachians 450 250MYA Fault block mountains Half grabens Basin and range Principle of isostasy Isostatic adjustment cid 127 Gravitational collapse Isostasy Principle of isostasy Isostatic adjustment floating crust on high density mantle in