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This article provides an in-depth exploration of geological provinces, hot spots, and the formation of volcanoes. It also discusses the properties of water, including surface tension, viscosity, changes in state, heat capacity, and solvent properties. The role of dissolved salts, salinity, and density in water is also examined, along with the impact of dissolved gases, transparency, and pressure. The circulation of water and the Coriolis effect are also discussed.
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Geology • Geological Provinces • Hot Spots • Stationary locations where magma rises from mantle • Heat crust, producing volcano • Crust moves over mantle • Forms chain of volcanoes, seamounts, islands • Hawaiian Islands • Hawaiian Ridge • Emperor Seamounts
Water • Properties • Polar • Water molecules attract each other • Hydrogen Bonding • Water tends to be “sticky” due to weak bonds Fig. 3.1
Water • Properties • Surface Tension • Stickiness at the surface due to cohesion • Water surface can support weight of very small organisms • Air-water interface supports numerous organisms • Microbes in surface films • Viscosity • Stickiness to objects due to adhesion • Objects moving through water drag some water with them • Changes in State • Fresh water reaches maximum density at 4 oC • Sea water gets denser as it cools • Ice is less dense than liquid water
Water • Properties • Heat Capacity • Water requires an unusually large amount of heat to raise its temperature • Energy needed to break hydrogen bonds • High latent heat of melting/fusion • High latent heat of evaporation (evaporative cooling) • Ocean tends to have a stable temperature • Solvent Properties • Electrical charges on water (polar molecule) • Help to pull apart molecules held together by electrical charge (salts) • Charged ions dissociate in water
Water • Dissolved Salts • Mostly derived from weathering of rocks on land, hydrothermal vents, volcanic ejecta and precipitation
Water • Dissolved Salts • Constituents • Salinity = salt content • Usually expressed in ‰ (g per kg) • “Average” sea water ~34.7 ‰ • 33-37 ‰ in open ocean • higher in enclosed seas • lower in areas with extensive river runoff • Fresh water < 0.5 ‰ • Brackish water – 0.5-17 ‰ • Six ions make up 98% of total dissolved solids in sea water • Most major constituents used by organisms
Water • Dissolved Salts • Constituents • Rule of Constant Proportions • Salinity may change from place to place, but proportions of major ions remain constant • Makes it easier for marine organisms to regulate their physiology • Salinity affected by • Evaporation • Precipitation • Ice formation
Water • Properties • Density • Determined by salinity and temperature • Temperature more influential than salinity • Increases with depth where water column is stable • Dissolved Gases • Most important • O2 – Used for respiration, produced by photosynthesis • CO2 – Used for photosynthesis, produced by respiration • N2 – Used as a nutrient in metabolism • Exchanged between ocean and atmosphere (gas exchange) • More soluble at lower temperatures • Concentrations impacted by biological activity • Transparency • Penetration of light • Affects • Photosynthesis • Vision • Behavior • Spectral attenuation
Secchi Disk Fig. 3.12
Fig. 3.14 • Water • Properties • Density • Dissolved Gases • Transparency • Pressure • Changes predictably with depth • 10 m = 1 atmosphere (14.7 psi) • Affects gas-filled structures • Constrains vertical movements of many animals
Circulation • Coriolis Effect • Affects motion of winds, currents and tides • Caused by rotation of earth • N. Hemisphere – Deflects motion to right • S. Hemisphere – Deflects motion to left