AIM: Introduce you to scientific study of oceans and seas Oceans and seas cover about 70% of the earth's surface Huge volume of water moderates temperatures on earth (enabling organisms like us to survive) Oceans are a tremendous source of food reserves Oceans are a huge source of mineral reserves Oceans are potentially a significant source of energy Oceans are a place for us to dump our garbage

Material covered by SFW What are the shapes or configurations of the modern ocean basins? What is the chemical make-up and physical nature of sea water? How do physical and chemical properties affect, and are in turn affected by, ocean currents? What is the origin of the tides and waves? Did the configuration of, chemistry of, or currents in ancient ocean basins differ from those in modern oceans?

Material covered by KPH How are organisms distributed in modern oceans? How do changes in the chemical composition and physical character of sea water affect the distribution of life in the oceans? Has marine life changes through time, and if so how? How have humans affected the oceans, and how might humans continue to affect the oceans?

Ocean floors are markedly different from the land we see around us Sea water hides some of the most striking geomorphic features on the surface of the earth Submarine canyons Mid-ocean ridges Oceanic fracture zones Deep-ocean trenches These features have no direct analogs on continents

Once earth scientists recognized those features, they were forced to change the way they organized their thoughts about geologic processes Investigations in marine geology were fundamental to the development of plate tectonic theory, the currently-accepted theoretical framework for geological thought

You will be successful in marine science to the extent that you too can adopt a marine perspective on earth Having raised the issue of perspective, let continue in that vein with a few additional thoughts on how perspective shapes scientific thought

The adoption of plate tectonic theory by earth scientists is sometimes cited as a classic example of what the historian of science Thomas Kuhn calls a paradigm shift Kuhn outlined his ideas on paradigm shifts in a widely read and often-cited book entitled ‘The structure of scientific revolutions’

Scientific revolutions, I Science does not grow by slow, steady, directionless accretion Science is a discontinuous process, directed along certain paths by ruling paradigms Paradigm here denotes how a community utilizes a commonly-accepted interpretation or guiding principle to understand a phenomenon or set of phenomena e.g. Thompson’s versus Bohr’s versus the quantum mechanical view of the atom Scientific revolutions occur as paradigm shifts

Scientific revolutions, II There is not, nor can there be, a reconciliation of conflicting hypotheses, i.e. the old and new paradigms, by some higher authority Ruling paradigms change quickly by ‘gaining the consent of the relevant community’ In this sense, ‘revolutionary’ is not a promotional term ‘Revolutionary’ is the technical description of the process by which science moves ahead

Special earth sciences perspectives Many earth scientists use an observation-inference methodology instead of experimental methodologies Observe and describe objectively features or processes Interpret features in light of the processes inferred to operate (or have operated) to generate them (using principles from biology, chemistry, or physics) ‘Test’ inferences by making ‘predictions’ Compare ‘predictions’ with observations

Methodology leads to the tenet ‘the present is the key to the past’ Observe geologic processes that occur on earth today, and determine how those processes affect rocks at the present time Assume that analogous processes operated at different times in the past, i.e. throughout geologic time Infer, by comparing modern and ancient rocks, which processes were responsible for forming ancient rocks

Marine geology and the earth system

Global topography Highest elevation - Mount Everest ~29,000 ft above sea level ~5.5 miles above sea level ~8.85 km above sea level Greatest depth - Marianas/Philippine trench ~38,000 ft below sea level ~7.5 miles below sea level ~11 km below sea level Total range = ~13 miles or ~20 km

Radius of earth = 6371 km (3982 mi) 20 km (13 mi) is a large distance to us. Relative to earth’s radius, however, 20 km is small. Radius of earth = 6371 km (3982 mi) Diameter of earth ≈ 12,700 km 20 km /6400 km ≈ 0.003 20 km ≈ 0.03% Earth’s radius

What is the distribution of elevations on earth? Is land area distributed ‘normally’ between the two extreme elevations? No - elevation distribution is bimodal One common elevation, just above sea level, corresponds to the elevation of continents A second common elevation, between 3-4 km below sea level, corresponds to the elevation of the ocean floors

Greatest changes in average elevation occur between 1 and 3 km below sea level The best place to locate the transition from continent to ocean is, then, somewhere between 1 and 3 km below sea level We place the ends of continents at 1 to 3 km below sea level