Lecture 24

Lecture 24 - Observe the seafloor around Monterey Bay,...

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Unformatted text preview: Observe the seafloor around Monterey Bay, California 10.00.a1 Monterey Bay lf she l nta ine ont C e lop s tal n ine t on C Monterey Monterey submarine canyon canyon Fault Fault cutting seafloor seafloor Observe this geologic map of the Monterey Bay of area area Cenozoic marine Cenozoic sediments in yellow, tan, brown brown 10.00.a2 Faults cut Faults across seafloor across Deep part of canyon is Deep hard Mesozoic granite hard How We Study the Seafloor Use sound waves Use to map depths to Use submersibles to observe Use and collect rocks and Use ships to drill Use holes in ocean floor holes 10.01.a What We Can Learn from Drilling Type of sediment or rock Fossils (age and environment) Determine isotopic ages and can get rate of deposition = Determine thickness/time span thickness/time 10.01.b Observe this seismic-reflection profile of the ocean Observe floor. Can you see each feature that is labeled? floor. 10.01.d1 Earth’s Magnetic Field Normal magnetic field 10.02.a Liquid outer core contains Liquid convection currents convection Reversed magnetic field Time 1: Time normal polarity polarity Observe how Observe magnetic reversals are recorded by a mid-ocean ridge mid-ocean Time 2: Time reversed polarity polarity Build series Build of magnetic stripes over time time 10.02.c Magnetic Stripes on Seafloor 10.02.d Observe what features are present in mid-ocean ridges Fissure eruptions Fissure in rift in alts ow bas Pill Dikes Form a consistent Form sequence of rocks in oceanic crust oceanic Lithospheric Lithospheric mantle mantle Asthenosphere Magma Magma chamber chamber 10.03.a1 Observe important features of the deep seafloor Seamount Abyssal plain Abyssal Mid-ocean Mid-ocean ridge ridge ar c Is la nd Accretionary Accretionary prism prism O ce an ic t re nc h 10.04.a1 Observe sediment thicknesses on the ocean floor (red is Observe thickest; white is thinnest). What settings have the thickest or thinnest sediment? thickest 10.04.a2 Thickest along Thickest passive continental margins Thinnest near Thinnest mid-ocean ridges ridges Thick offshore of large rivers large Observe a map showing depth of the seafloor Observe Compare the relationship between depth and age Deepest seafloor Deepest is oldest is Mid-ocean ridges Mid-ocean less deep because young because Depth (dark is deep) Age increases systematically out from ridge out Age patterns Age truncated at trenches trenches 10.04.a Age (orange is young) 10.05.a Observe how flat-topped Observe seamounts form seamounts Volcano rises above Volcano the sea as an island an Eruptions of Eruptions lava onto seafloor lava Top of mountain Top beveled off by waves; island subsides below sea subsides Oceanic Plateaus Kerguelen oceanic Kerguelen plateau plateau 10.05.b Rising mantle Rising plume at hot spot spot Submarine flood Submarine basalts pour onto seafloor seafloor Plateau forms Plateau over several million years Observe the location of hot spots, linear island chains, Observe and oceanic plateaus and Iceland Azores Ontong Java Plateau Plateau Hawaii Galapagos Tahiti Easter Easter Island Island Canary Canary Island Island Afar Tristan Tristan da Cunha da Kerguelen Kerguelen Plateau Plateau 10.05.c1 Observe the processes that form island arcs Oce anic crus t Litho sphe ric m antle ic an e Oc h nc tre c ar d an Isl Asthenosphere Melting of Melting mantle mantle Lithospheric Lithospheric mantle mantle Asthenosphere Asthenosphere 10.06.a1 Observe what happens in front of Observe and behind an island arc and h nc e Tr c ar d an Isl c ar ck Ba g din a re sp k k bac bac ro l rolll nch nch Tre Tre 10.06.b1 Why Are Island Arcs Curved? Siberia Aleutian island arc Aleutian Aleutian Aleutian trench trench Alaska 10.06.c More surface More area on outside than at depth at Earth is a sphere, Earth not a flat plane not Observe the location of the main island arcs Japan Aleutian Lesser Lesser Antilles Antilles Aegean Mariana Philippines Philippines SumatraJava Tonga Scotia 10.06.d1 Observe some smaller seas of the Pacific Bering Sea: New subduction farther from coast Philippine Sea: Back-arc spreading Asia Sea of Japan: Back-arc rifting Australia 10.07.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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