A short history of marine geology

A short history of marine geologyincluding some of the development of the theory ofplate tectonics1

Why history?• Marine Geology is a young field – and some of the “old”ideas might have a “come back”• To be aware of the difficulties and uncertainties in decipheringdynamic processes in the ocean• To appreciate the development of global plate tectonics, anexcellent example of how science works2

Early/mid-19th century ideas• The ocean floors were featureless and uninteresting “deserts ofthe deep-sea”• The deep oceans were without life3

What was the basis of these ideas?• The deep ocean was very difficult to observe– difficulties of navigation– difficulties of measuring depth– difficulties of taking sea floor samples• Technical advances were necessary to overcome theseproblems and to collect sufficient data for new ideas4

1850-1870Transatlantic Cooperation1857-1866 Cyrus Field & IsambardKingdom BrunelOn July 27 th 1866 the second transatlanticcable crossed 5000 km from Ireland to NewFoundland (the first one failed in 1864).Brunel5

(1858)The first industrialstimulus: thetransatlantic cablesCyrus West Field, US businessman, teams up withWilliam Thomson (UK), the future Lord Kelvin :first industry-academia cooperation on the oceanThe Great Eastern, floating palace(Jules Verne’s Une ville flottante)reshaped into a giant cable layer.Landing of the new (first) cable inNewfoundland, 9 september 18646

The depth of the oceansFirst known attempt:• Magellan (early 1500’s) tried to measure the depth of the seafloor in the central Pacific but it was too deep for his soundinglines7

Measuring depth• The original and long-standing (until the 1920’s) method was“plumbing the depths” by lowering a lead way on a line• Problems:– very long ropes were necessary, not available on manyships– very laborious/time consuming to hoist the long heavy rope– bottom impact difficult to detect with the heavy rope– the long time of lowering resulted in big errors due tocurrent movements8

Measuring depth• Development of new technology was driven by the need forbathymetric information for laying trans-Atlantic telephonecables• A major advance in the second half of the 19th century (1870)was the introduction off steel cable– it is lighter (because thinner) per length unit than rope– it is less likely to break than hemp ropes9

1870-1910“Oceanic Golden Age”- wireline depth measurements1891 Murray & Renard - descriptionof sediments of ocean basins andContinental Margins based on the“Challenger expedition 1872-1876”1904 Fridtjof Nansen - formation ofthe Continental Shelf and PolarSeas based on the “Framexpedition 1893-1896”10

First bathymetric map of an ocean• Matthew Fontaine Maury, U.S. Navy lieutenant (“Father ofOceanography”), was a leader in bathymetric surveying for theNavy• Based on less than 200 soundings, he presented the Mid-Atlantic Ridge morphology• He published in 1855 the map on the next slide. This mappresented the first indication of the the shelf, continental rise,abyssal plain and a Mid-Oceanic Ridge.11

Maury’s map of the North AtlanticOpen University, 1989 12

Maury - bathymetric section betweenTampico and Africavertical exaggeration ~ 500xOpen University, 1989 13

The Fram ExpeditionFridtjof Nansen (1861-1930)Expedition lasted from 1893-1896Nansen discussed problems such as:• sea level change• glacial erosion• deposition• continental slope• shelf sediment dynamics14

The Challenger Expedition• Lasted over three years(1872-1876)• Organized and funded bythe British government• Leader: Charles WyvilleThompson, University ofEdinburghHMS Challenger15

The route of HMS ChallengerOpen University, 1989 16

HMS Challenger results17

Challenger - geological results18

Turn of the century• Work continued on bathymetry. The first General BathymetricChart of the Oceans (GEBCO) was printed in 1903• Some work was done on surface sediments, but this wasentirely based on dredging and core samples• Radioactivity was discovered by Marie and Pierre Curie. Thishad fundamental impact on earth sciences later on, when it wasused for absolute age dating19

1915 - Continental drift• Alfred Wegener, an Austrian(german) meteorologistproposed in “The origins ofcontinents and oceans” thatcontinents were previouslyjoined in a single land mass andhad been drifting apart since180 Ma ago• His work was inspired by thelong suspected fit betweenAfrica and South America, butit was rejected because he couldnot come up with a reasonablemechanismAlfred Wegener (1880-1930)The Sea Floor, 1989 20

Wegener’s evidence• Fit of continents• Paleontological (fossil)observations• Geological observations(rock types, coal deposits)• Indications of glaciationsThis dynamic Earth, USGS 21

Wegener’s problems• Major opposition to Wegener’s ideas was due to his lack ofa plausible physical mechanism to account for the drift - heproposed that continents plowed through the ocean floor• A previous explanation for the geological and fossilevidence was equally implausible, involving previouslyemergent land bridges• A major impediment to the acceptance of Wegener’shypothesis was a lack of adequate knowledge of theoceans.22

Wegener’s prophecy23

1920-1930“Exploring the oceans”- the echosounding revolution1929 Dansgard – Monaco OceanographicInstitution increases EuropeanContinental Margin geologicaland oceanographic mappingR/V Armauer Hansen1925-1927 R/V Meteor Atlantic expedition1934 R/V Discovery expedition1935 R/V Snellius expedition24

Echo soundingThe Sea Floor, 1989 25

1930-1940Foundation of marine geology institutionsand mapping of the ocean floorHoltedahl1930 Vening Meinesz – gravity investigationsfor crustal studies1933 Holtedahl - Shepard discussion:Norwegian Channel due to glaciationor tectonics?1932 Trask - marine environments in whichpetroleum accumulates1938 Shepard & Beard – submarine canyons1938 Ewing & Vine – seismic refraction26

Marine gravity measurements27

1940-1950Sampling the ocean floorGuyot development1941 Emery and Dietz – gravity coringinstruments1942 Sverdrup - the ocean’s physicsand chemistry1946 Hess – flat topped submarinevolcanoes (guyots): trigger forsea floor spreading ideas1947 Kullenberg – improvements of sediment sampling1947-1948 Swedish RV Albatross expedition1948 Shepard - submarine geology28

Sediment coring29

1950-1960“Evolutionary models for planet earth”1956 Bullard et al., heat flow1956 Runcorn, paleomagneticestablishing divergent drift betweenNorth America and Europe1958 McClure et al., single channelreflection seismic recordings1958 THE GENEVA CONFERENCE ON THELAW OF THE SEAMaurice Ewing (1903-1976)1959 Ewing – Norwegian Margin seismicrefraction studies showed that morethan 4000 m of sediments overlybasement30

1960-1970“plate tectonics and sea-floor spreading”hydrocarbon exploration in Europeinternational Deep-Sea DrillingTransform faults1960 Commercial exploration in the North Sea1961 Dietz – continent and ocean basinevolution1962 Hess – history of ocean basins1962 First Atlantic US Margin programme1963 Bouma – Turbidite sequences1965 Wilson – transform faults, oceanic ridges, and magneticanomalies1965 Bullard – the fit of the continents around the Atlantic1965 Heezen & Tharp – tectonic fabric of the Atlantic31

Bruce Heezen and Marie Tharp- physiographic maps of the oceans32

Sea floor spreading and magneticstripesThis dynamic Earth, USGS 33

Magnetic anomalies - symmetry• This fairly complicatedversion was the first suchdata collected (Wilson,1965, Vine, 1966)• Observation of magneticanomalies on the sea floor -alternating strips of rockwith normal and reversedpolarity, symmetric aroundridgesThis dynamic Earth, USGS 34

1960-1970“plate tectonics and sea-floor spreading”hydrocarbon exploration in Europeinternational Deep-Sea DrillingSea-floor spreading magnetic anomalies1965 First continental shelf committee inNorway, planning of seismic investigations1966 Vine – sea-floor spreading frommagnetic anomalies1967 Menard – sea-floor spreading andtopography1967 Seismic studies off Norway indicate thick sediments1968 LePichon – sea-floor spreading and continental drift1968 Deep-Sea Drilling Project1969 Ekofisk field discovered after 33 dry holes35

Magnetic reversals• Meanwhile, the existenceand timescale of magneticfield reversals was beingindependently explored,first on continental lavas,then on marine sedimentsand basalts• The plot shows magneticreversals and their dates forthe last 3.5 Ma36

The 1960’s sea floor spreading37

Continued...38

Deep sea drillingPhoto: This dynamic Earth, USGS 39

Crucial findings of the first DSDPlegsThe Solid Earth, Fowler 40

Other geophysical support forplate tectonics• Global seismic networks for nuclear test monitoringrevealed a pattern in earthquake distribution: the plateboundaries41

1970-1980“International decade of Ocean Exploration”declared by the president of the United States1970 Beloussov - against sea-floor spreading1970 East Atlantic Continental MarginProgramme “Cambridge symposium”1972 Walton – concept of 3-D seismic surveys1972 Talwani & Eldholm – the evolution ofthe Norwegian Margin and theNorwegian-Greenland Sea1973 Norwegian Petroleum Directorate founded1977 Vail et al. – seismic stratigraphy and sea level curve1978 McKenzie’s simple shear model1979 Sclater – the history of the Atlantic42

1980-1990“Geodynamics and Ocean Drilling”JOIDES Resolution1980 Emery – Continental Marginclassification and petroleum1981/1982 Hinz / Mutter: discussionof seaward dipping reflectors1981 Le Pichon – Passive Margins:a formation model1985 Wernicke’s pure shear model1985 Ocean Drilling Program1987 Passive Margin Legs 103 (non-volcanicGalicia Bank) and 104 (volcanic Vøring Plateau)43

1990-2000“Quantification of marginprocesses”Satellite gravity1993 Mutter – Margins declassified1992 Nansen Arctic Drilling Programme1993-1999 European North AtlanticMargin Programme1994 UN convention on the Law of the Seas1997 Sandwell & Smith: global gravity remotesensing1997 Production of oil in the deep-waterCampos Basin, Brazil1999 Ocean Margin hydrodynamic systems1999 Ocean Margin Deep-Water ResearchConsortium and Joint Industry Partners44

Quo vadis?• Unravelling the mechanisms behind plate tectonics• Understanding the details of submarine features for examplemajor hydrocarbon provinces• Geohazards on margins: (e.g. seismogenic zones)• Sediment Dynamics• Margin response to rapid climate change• Fluid systems on margins: quantification, visualization, andimpact assessment• Margin’s Bacterial World: from deep to shallow biosphere45

Norwegian marine scientists• Nansen, Fridtjof (marine zoology, geology) 1890 proposed to build anice-going vessel – Maud.• Bjerknes, Vilhelm (atmosphere & ocean circulation), direct a newgeophysical institute in Leipzig, Germany• Sverdrup, Harald Ulrik (born 1888 in Sogndal) (atmosphere & oceancirculation) Director Scripps, USA• Sars, G.O. (Charles Wyville Thomson travels to Christiania (Oslo) to investigate the “living fossils”collected by Michael Sars’ son on the Norwegian margin, off the Lofoten – crinoids) (marine fossils)Questions:1. Which of the names is used for a research centre, a research vessel, or a oceanographic unit?2. Explain the unit for water masses.46

Suggested reading• Look at “This dynamic Earth”, an online text from the USGSat http://www.usgs.gov/publications/text/dynamic.html• Read through “Exploring the ocean basins with satellitealtimeter data”, an online text by Dave Sandwell and WalterSmith athttp://www.ngdc.noaa.gov/mgg/announcements/text_predict.HTML47