Sea-Floor Spreading, Subduction,& Plate Boundaries Lecture 23 Prop: Test 3 Invitations Geol 101 (Kite) Quiz 9, April 2005 ******************************* * You are cordially invited * Name * to attend the * * Geology 101 (Kite) TEST 3 * * 10:00 a.m. * Student ID * Tuesday, 18 April 2006 * * 21 White * * * * RSVP, regrets only * ******************************* Bring this Invitation/Quiz to the Third Test on 18 April. You must be in class to pick up an invitation. If not download it from the Test and Quizzes Page Geol 101 (Kite) Quiz 9, April 2006 ******************************* * You are cordially invited * Name * to attend the * * Geology 101 (Kite) TEST 3 * * 10:35 a.m. * Student ID * Tuesday, 18 April 2006 * * 21 White * * * * RSVP, regrets only * ******************************* Bring this Invitation/Quiz to the Third Test on 18 April. You must be in class to pick up an invitation. If not download it from the Test and Quizzes Page 1
Alfred Wegener s Evidence for Continental Drift 1. Continental Fit 2. Similar Rocks, Ages 3. Similar Fossils 4. Widespread Glaciation Pangaea = Gondwanaland + Laurasia Source: http://vishnu.glg.nau. edu/rcb/penn.jpg Alfred Wegener s Evidence for Continental Drifts Was NOT Accepted in USA. Problem: No Mechanism for Continents to Plow Through Oceanic Crust Answer lies on & in the Sea Floor - Ch. 18 + 19 in Text 2
Spongebob Theme Song Lyrics Are ya ready kids? Aye Aye Captain! I CAN'T HEAR YOU! AYE AYE C APTAIN! ohhhhhh!!!! Who lives in a pineapple under the sea? SPONGEB OB SQUAR EPANTS! Absorbant and yellow and poreous is he SPONGEB OB SQUAR EPANTS! His nautical nonsense be somethin you wish SPONGEB OB SQUAR EPANTS! Then drop on the deck and flop like a fish! SPONGEB OB SQUAR EPANTS! Ready? SPONGEB OB SQUAR EPANTS! SPONGEB OB SQUAR EPANTS! SPONGEB OB SQUAR EPANTS! SPONGEYB OB SQUAR EPAAAANTS http://www.spe.sony.com/movies/da sboot/ WW II http://www.geocities.com/pentagon/2560/bowph1.jpg Submarine Science Mapping of Ocean Basins http://members.microdsi.net/shirschm/welcome.index.html Seismic & Sonar Study Reveals Sea-Floor Topography Geophysicists s Answers Life s Important Questions Know these mega-scale Landforms Continental Shelf Continental Slope Continental Rise Abyssal Plain Mid-Ocean Ridge (~ Mid-Ocean Rise) Trench Know differences between Oceanic Crust and Continental Crust 3
Ocean Basin Bathymetry See Figures 18.5 to 18.16 in Plummer & Others 10 th ed. Ocean Basin Bathymetry See Figures 18.5, 18.15 in Plummer & Others 10 th ed. Cold War More Submarine Science Magnetic Anomalies in Ocean Basin 4
Deep-Sea Magnetic Anomalies Deep Sea Drilling Project (DSDP) Studied Geology of Ocean Basins Continental Record = Incomplete Deep Ocean Basin Record Was Thought to be More Complete Glomar Challenger Harry Hess Magnetic Anomalies: Atlantic Ocean South of Iceland New Ocean Crust Created at Mid-Ocean Ridges: Spread Centers 5
DSDP Surprise Finding: Ocean Basins are <200,000,000 y Old Much Younger than the Continents Very Young Sediments at the Mid Ocean Ridges Age of the Ocean Basins Birth of an Ocean Basin? Spreading at the Red Sea: Break-Up of Asia and Africa Note a Failed Arm of Rifting in East Africa 6
Break-Up of a Continent and Origin of an Ocean Basin Problem: If New Crust is Created at Mid- Ocean Ridges, Where is Old Crust Consumed to Balance the New Crust? Where is Old Crust Consumed to Balance the New Crust? Answer Lies in Deep-Focus Earthquakes. 7
Earthquakes Occur in Brittle (Elastic) Lithosphere Lithosphere Asthenosphere 70-100 km Distribution of All Earthquakes (Deep and Shallow Focus) Subduction Zones: Ocean-Ocean Margin 8
Subduction Zones: Ocean-Continent Margin Deep-Focus Quakes Only in Subduction Zones Isotherms in Subduction Zones 600 o C 400 o C 9
Japan Trench & Volcanic Arc Back-Arc and Fore-Arc Basins See Figure 19.35 in Plummer & Others 9 th ed. Subduction Zones & Volcanoes 10
Spread Centers Feed Subduction Zones Missing Mechanisms for Continental Drift: Sea Floor Spreading & Subduction Continents are Passive Boats How Are Mountains Built? Himalayas 11
Orogeny (Mountain Building) in the Himalayas Continental Lithosphere Will NOT Flush Down Subduction Zones Orogeny in the Himalayas 12
Orogeny in Himalayas Orogeny in Himalayas Orogeny in the Himalayas 13
Orogeny - Mountain Building - Sediment Supply Orogeny - Mountain Building - Glaciation Plate Margins: Spread Centers (Mid-Ocean Ridges) Subduction Zones (Trenches) Transform Faults 14
Plate Margins: Transform Faults & Fracture Zones Transform Faults 15
San Andreas Fault: Right-Lateral Transform Fault Left-Lateral Offset!! Why?: Fault is Produced by Offset, vs. Offset Produced by Fault Transform Faults: Offsets in Spread Centers Plate Motion on a Sphere 16
Plate Motion on a Sphere Requires Transform Faults Because of Different Rates of Motion The Plates The Plates: Pacific-Centered View (Distorted by Mercator Map Projection) 17
What Drives Plate Tectonics? 1. Convection Cells in Mantle 2. Sinking of Cool, Dense Plates 3. Mantle Plumes - Hot Spots Convection Cells 18
Convection Cells in Mantle Mantle Plumes 19
Mantle Plumes Under Continents Known Hot Spots Hawaiian Islands 20
Mantle Plumes - Hot Spots Numbers = Age of Rock in Millions of Years Sinking of Cool, Dense Plates Seamount Volcanoes Surrounded by Fringing Coral Reefs 21
Atolls: Submerged Volcanos Support Reefs Only in Warm Clear Seas Tuamoto Islands NASA Quiz 9 Chapters on Test III on 18 April CH 11-19 NOT Chapter 20 Save Questions 6, 7-10 and 12 for Quiz 10 Turn Whole Quiz 9 in at the test, We will provide a new Quiz 10 on 25 April 22