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A short history of marine geology

including some of the development of the theory of plate tectonics

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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 deciphering dynamic processes in the ocean

• To appreciate the development of global plate tectonics, an excellent example of how science works

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Early/mid-19th century ideas

• The ocean floors were featureless and uninteresting “deserts of the deep-sea”

• The deep oceans were without life

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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 these problems and to collect sufficient data for new ideas

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1850-1870Transatlantic Cooperation

1857-1866 Cyrus Field & Isambard Kingdom Brunel

On July 27th 1866 the second transatlantic cable crossed 5000 km from Ireland to New Foundland (the first one failed in 1864).

Brunel

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(1858)

The first industrial stimulus: the transatlantic cables

Cyrus West Field, US businessman, teams up with William Thomson (UK), the future Lord Kelvin : first industry-academia cooperation on the ocean

The Great Eastern, floating palace (Jules Verne’s Une ville flottante) reshaped into a giant cable layer.

Landing of the new (first) cable in Newfoundland, 9 september 1864

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The depth of the oceans

• Magellan (early 1500’s) tried to measure the depth of the sea floor in the central Pacific but it was too deep for his sounding lines

First known attempt:

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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 many

ships– 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 to

current movements

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Measuring depth

• Development of new technology was driven by the need for bathymetric information for laying trans-Atlantic telephone cables

• 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 ropes

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1870-1910“Oceanic Golden Age”- wireline depth measurements

1891 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”

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First bathymetric map of an ocean

• Matthew Fontaine Maury, U.S. Navy lieutenant (“Father of Oceanography”), was a leader in bathymetric surveying for the Navy

• Based on less than 200 soundings, he presented the Mid-Atlantic Ridge morphology

• He published in 1855 the map on the next slide. This map presented the first indication of the the shelf, continental rise, abyssal plain and a Mid-Oceanic Ridge.

Open University, 1989 12

Maury’s map of the North Atlantic

Open University, 1989 13

Maury - bathymetric section betweenTampico and Africa

vertical exaggeration ~ 500x

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The Fram ExpeditionFridtjof Nansen (1861-1930)

Expedition lasted from 1893-1896

Nansen discussed problems such as:

• sea level change

• glacial erosion

• deposition

• continental slope• shelf sediment dynamics

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The Challenger Expedition

HMS Challenger

• Lasted over three years (1872-1876)

• Organized and funded by the British government

• Leader: Charles Wyville Thompson, University of Edinburgh

Open University, 1989 16

The route of HMS Challenger

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HMS Challenger results

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Challenger - geological results

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Turn of the century

• Work continued on bathymetry. The first General Bathymetric Chart of the Oceans (GEBCO) was printed in 1903

• Some work was done on surface sediments, but this was entirely based on dredging and core samples

• Radioactivity was discovered by Marie and Pierre Curie. This had fundamental impact on earth sciences later on, when it was used for absolute age dating

The Sea Floor, 1989 20

1915 - Continental drift• Alfred Wegener, an Austrian

(german) meteorologist proposed in “The origins of continents and oceans” that continents were previously joined in a single land mass and had been drifting apart since 180 Ma ago

• His work was inspired by the long suspected fit between Africa and South America, but it was rejected because he could not come up with a reasonable mechanism

Alfred Wegener (1880-1930)

This dynamic Earth, USGS 21

Wegener’s evidence

• Fit of continents

• Paleontological (fossil) observations

• Geological observations (rock types, coal deposits)

• Indications of glaciations

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Wegener’s problems• Major opposition to Wegener’s ideas was due to his lack of

a plausible physical mechanism to account for the drift - he proposed that continents plowed through the ocean floor

• A previous explanation for the geological and fossil evidence was equally implausible, involving previously emergent land bridges

• A major impediment to the acceptance of Wegener’s hypothesis was a lack of adequate knowledge of the oceans.

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Wegener’s prophecy

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1929 Dansgard – Monaco OceanographicInstitution increases EuropeanContinental Margin geologicaland oceanographic mapping

1925-1927 R/V Meteor Atlantic expedition1934 R/V Discovery expedition1935 R/V Snellius expedition

1920-1930“Exploring the oceans”

- the echosounding revolution

R/V Armauer Hansen

The Sea Floor, 1989 25

Echo sounding

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1930 Vening Meinesz – gravity investi-gations for crustal studies

1933 Holtedahl - Shepard discussion:Norwegian Channel due to glaciationor tectonics?

1932 Trask - marine environments in whichpetroleum accumulates

1938 Shepard & Beard – submarine canyons1938 Ewing & Vine – seismic refraction

1930-1940Foundation of marine geology institutions

and mapping of the ocean floor

Holtedahl

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Marine gravity measurements

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1941 Emery and Dietz – gravity coringinstruments

1942 Sverdrup - the ocean’s physicsand chemistry

1946 Hess – flat topped submarinevolcanoes (guyots): trigger forsea floor spreading ideas

1947 Kullenberg – improvements of sediment sampling1947-1948 Swedish RV Albatross expedition

1948 Shepard - submarine geology

Guyot development

1940-1950Sampling the ocean floor

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Sediment coring

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Maurice Ewing (1903-1976)

1950-1960“Evolutionary models for planet earth”

1956 Bullard et al., heat flow

1956 Runcorn, paleomagnetic establishing divergent drift between North America and Europe

1958 McClure et al., single channel reflection seismic recordings

1958 THE GENEVA CONFERENCE ON THE LAW OF THE SEA

1959 Ewing – Norwegian Margin seismic refraction studies showed that more than 4000 m of sediments overly basement

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1960 Commercial exploration in the North Sea1961 Dietz – continent and ocean basin

evolution1962 Hess – history of ocean basins1962 First Atlantic US Margin programme1963 Bouma – Turbidite sequences

1965 Wilson – transform faults, oceanic ridges, and mag-netic anomalies

1965 Bullard – the fit of the continents around the Atlantic1965 Heezen & Tharp – tectonic fabric of the Atlantic

Transform faults

1960-1970“plate tectonics and sea-floor spreading”

hydrocarbon exploration in Europeinternational Deep-Sea Drilling

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Bruce Heezen and Marie Tharp - physiographic maps of the oceans

This dynamic Earth, USGS 33

Sea floor spreading and magnetic stripes

This dynamic Earth, USGS 34

Magnetic anomalies - symmetry

• This fairly complicated version was the first such data collected (Wilson, 1965, Vine, 1966)

• Observation of magnetic anomalies on the sea floor -alternating strips of rock with normal and reversed polarity, symmetric around ridges

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1965 First continental shelf committee inNorway, planning of seismic investigations

1966 Vine – sea-floor spreading frommagnetic anomalies

1967 Menard – sea-floor spreading andtopography

1967 Seismic studies off Norway indicate thick sediments1968 LePichon – sea-floor spreading and continental drift1968 Deep-Sea Drilling Project1969 Ekofisk field discovered after 33 dry holes

Sea-floor spreading magnetic anomalies

1960-1970“plate tectonics and sea-floor spreading”hydrocarbon exploration in Europeinternational Deep-Sea Drilling

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Magnetic reversals

• Meanwhile, the existence and timescale of magnetic field reversals was being independently explored, first on continental lavas, then on marine sediments and basalts

• The plot shows magnetic reversals and their dates for the last 3.5 Ma

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The 1960’s sea floor spreading

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Continued...

Photo: This dynamic Earth, USGS 39

Deep sea drilling

The Solid Earth, Fowler 40

Crucial findings of the first DSDP legs

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Other geophysical support forplate tectonics• Global seismic networks for nuclear test monitoring

revealed a pattern in earthquake distribution: the plate boundaries

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1970 Beloussov - against sea-floor spreading1970 East Atlantic Continental Margin

Programme “Cambridge symposium”1972 Walton – concept of 3-D seismic surveys1972 Talwani & Eldholm – the evolution of

the Norwegian Margin and theNorwegian-Greenland Sea

1973 Norwegian Petroleum Directorate founded1977 Vail et al. – seismic stratigraphy and sea level curve1978 McKenzie’s simple shear model1979 Sclater – the history of the Atlantic

1970-1980“International decade of Ocean Exploration”

declared by the president of the United States

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1980 Emery – Continental Marginclassification and petroleum

1981/1982 Hinz / Mutter: discussionof seaward dipping reflectors

1981 Le Pichon – Passive Margins:a formation model

1985 Wernicke’s pure shear model

1985 Ocean Drilling Program1987 Passive Margin Legs 103 (non-volcanic

Galicia Bank) and 104 (volcanic Vøring Plateau)

JOIDES Resolution

1980-1990“Geodynamics and Ocean Drilling”

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1993 Mutter – Margins declassified1992 Nansen Arctic Drilling Programme1993-1999 European North Atlantic

Margin Programme1994 UN convention on the Law of the Seas1997 Sandwell & Smith: global gravity re-

mote sensing1997 Production of oil in the deep-water

Campos Basin, Brazil1999 Ocean Margin hydrodynamic systems1999 Ocean Margin Deep-Water Research

Consortium and Joint Industry PartnersSatellite gravity

1990-2000“Quantification of margin

processes”

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Quo vadis?• Unravelling the mechanisms behind plate tectonics

• Understanding the details of submarine features for example major hydrocarbon provinces

• Geohazards on margins: (e.g. seismogenic zones)

• Sediment Dynamics

• Margin response to rapid climate change

• Fluid systems on margins: quantification, visualization, and impact assessment

• Margin’s Bacterial World: from deep to shallow biosphere

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Norwegian marine scientists• Nansen, Fridtjof (marine zoology, geology) 1890 proposed to build an

ice-going vessel – Maud.

• Bjerknes, Vilhelm (atmosphere & ocean circulation), direct a new geophysical institute in Leipzig, Germany

• Sverdrup, Harald Ulrik (born 1888 in Sogndal) (atmosphere & ocean circulation) 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.

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Suggested reading

• Look at “This dynamic Earth”, an online text from the USGS at http://www.usgs.gov/publications/text/dynamic.html

• Read through “Exploring the ocean basins with satellite altimeter data”, an online text by Dave Sandwell and Walter Smith at http://www.ngdc.noaa.gov/mgg/announcements/text_predict.HTML