John Grotzinger Thomas H Jordan Frank Press and
- Slides: 34
John Grotzinger, Thomas H. Jordan, Frank Press and Raymond Siever, Understanding Earth Fifth Edition Chapter 17: Earth Beneath the Oceans Copyright © 2004 by W. H. Freeman & Company
Marine Geology • Most of the world is under water -- 71% • Plate Tectonics came about mainly from the study of marine geology
Major Differences between the Ocean Floor and the Surface of Continents Continental surfaces are a source of sediment, that is they are regions where erosion and weathering prevail. Continents are ~4 by old Ocean floors are regions where net sedimentation and volcanism prevail. Oceans are no more that 200 Myr old
About Oceanic Geology • Volcanism dominates near oceanic ridges and hot spots. • Sedimentation dominates elsewhere • Older volcanic crust usually has a thicker pile of overlying sediments
How have earth scientists learned about the depths of the world’s oceans? HMS Challenger, 1872 throughout a 4 year voyage, used rope lines to estimate ocean depths. Today we use echo sounders, devices that emit a pinging sound and record its return later in time. Knowing the speed of sound and the time of flight of these echoes can be used to calculate water depths.
How have earth scientists learned about the geology of the world’s oceans? • Submersibles-- e. g. Johnson Sea. Link, Alvin -- biology, petrology • Academic Drilling- DSDP, ODP, IODP • Commercial drilling and seismic exploration for oil and gas • Swath Mapping--Beams of sound (many pings in many directions received at many stations on the underside of a vessel) -bathymetry • seismometer stations around the world
How have earth scientists learned about the geology of the world’s oceans? Satellites data can be used to make bathymetric maps • Satellites can access the most remote parts of the world • Satellites can detect ocean surface elevation. • Ocean height depends on waves, currents, and the underlying topography (bathymetry)
A “typical” oceanic bathymetric profile across two plates that are diverging …. . The Atlantic Ocean • is 5000 km across • is shallowest in the center (2500 m deep) and deeper along its flanks in the abyssal plain
Key Features across the Atlantic Seafloor • a continental shelf ( < 200 m water depth) that is often cut by submarine canyons • A continental slope ( > 200 m, 4 degrees dip, i. e. 70 m drop per 1 km run) • A continental rise (2000 -3000 m) • An abyssal plain (4000 -6000 m) • Seamounts - extinct underwater volcanoes • Mid-oceanic Ridges - active underwater mountain chain
Key Features across the Pacific Seafloor • Trenches • seamounts • guyots - flat-topped extinct marine volcanoes, flat-topped because they were once above sea-level and were eroded
A Great Discovery • Life does not only derive from sunlight energy!
Sources of Deep-Sea Sediments Derive from (1) the dead skeletons of foraminifera (single -cell animals) that live in the (2) wind-borne or underwater-borne clays
Carbonate Compensation Depth (CCD) Below a certain depth (CCD), the skeletons dissolve back into sea water and do not make it into the sediment!
Wave Action • Waves in general, are created by wind • Wind velocity, area affected by winds and length of time that the wind blows are all factors that help to increase the height of a wave • Wave particle motion is circular at the surface to elliptical at the bottom • Waves that hit the coast at an angle created a longshore drift of sediments along the coast
Wave Action • Waves that hit the coast at an angle created a longshore drift of sediments along the coast
Tides • Tides can leave you high and dry, twice a day and can be intensified by local bathymetry • The largest tides occur when the sun and moon are aligned (spring tides) and the smallest are when the sun and moon are aligned at right angles to each other.
“The Beginning for a few is the End for Many”
- Forensic pathologist vs forensic anthropologist
- Frank william abagnale sr
- David john frank
- John locke vs thomas hobbes
- George washington vs king george iii venn diagram
- Paul l downing inventor mailbox
- Mad hedge fund trader
- Mad hedge fund trader
- Hobbes
- Hobbes and locke
- Chapter 19 section 3 freedom of speech and press
- Chapter 19 section 3 freedom of speech and press
- Telephone television radio and the internet
- Press and siever
- Press and siever
- Jordan university of science and technology
- Jordan university of science and technology
- Jordan university of science and technology
- Row operation method
- How does gatsby lose daisy in chapter 7
- Personality and its transformations
- Jordan food and drug administration
- World missionary press booklets
- Lost wax pattern
- Thermal press hair
- Penny press era
- The president together with his wife greet press cordially
- Sms extrusion press
- Smart bench press
- Drill press safety poster
- Rundown press conference
- Press tool design
- Ravne press
- Pine forge press
- Maria press