Chapter 3
Key Concepts
•
The world ocean has four main basins: the Atlantic, Pacific, Indian, and Arctic.
•
Life first evolved in the ocean.
•
The earth’s crust is composed of moving plates.
•
New seafloor is produced at ocean ridges and old seafloor is removed at ocean
trenches.
•
The ocean floor has topographical features similar to those found on continents.
•
The seafloor is composed of sediments derived from living as well as nonliving
sources.
•
Latitude and longitude determinations are particularly necessary for precisely
locating positions in the open sea, where there are no features at the surface.
World Ocean
•
Primitive earth and formation of the ocean
– early earth thought to be composed of silicon compounds, iron, magnesium
oxide, and other elements
– gradually, the earth heated, causing melting and separation of elements
– water vapor locked within minerals worked its way to the surface, where it
cooled, condensed, and formed the ocean
•
Ocean and the origin of life
– atmosphere formed by gases escaping from deep within the planet
– free oxygen formed oxides, oxygen did not accumulate until evolution of
modern photosynthesis
•
Ocean and the origin of life
– Stanley Miller’s apparatus
•
First cells were most likely anaerobic bacteria
•
The ocean today
– 4 major ocean basins:
• Pacific, Atlantic, Indian, Arctic
– Pacific Ocean - largest
– Arctic Ocean - smallest
– Seas - smaller than ocean, essentially landlocked
Continental Drift
•
Layers of the earth
– Inner core:
– Outer core:
– Mantle:
– Crust:
– Lithosphere:
– Asthenosphere:
•
Moving continents
– Alfred Wegener
– Continents fit together like pieces of jigsaw puzzle
•
•
•
•
– One supercontinent - Pangaea
– Laurasia and Gondwanaland
Forces that drive continental movement
– magma moves by convection currents
– midocean ridges
– at subduction zones
– seafloor spreading
Evidence for continental drift
– fit of continental boundaries
– earthquakes
– seafloor temperatures highest near ridges
– age of crust
Theory of plate tectonics
– lithosphere is viewed as a series of rigid plates separated by earthquake belts
– divergent plate boundaries: located at midocean ridges where plates move apart
– convergent plate boundaries: located at trenches where plates move toward
each other
– faults: regions where plates move past each other (e.g. transform faults)
– rift zones: where lithosphere splits
Rift (Deep Sea Vent) Communities
– specialized environments found at divergence zones of the ocean floor
– primary producers are chemosynthetic bacteria
Ocean Bottom
•
Ocean basin
– abyssal plains and hills
– seamounts
– ridges and rises
– trenches and island arcs
•
Life on the ocean floor
– continental shelves are highly productive
– life on the abyssal plains is not abundant, no sunlight, no photosynthesis
Composition of the Seafloor
•
Sediment—loose particles of inorganic and organic material
•
Hydrogenous sediments
– formed from seawater through a variety of chemical processes
– e.g. carbonates, phosphorites, manganese nodules
•
Biogenous sediments
– formed from remains of living organisms
– mostly particles of corals, mollusk shells, shells of calcium carbonate or
silicious planktonic organisms
•
Terrigenous sediments
– produced from continental rocks by the actions of wind, water, freezing,
thawing
– e.g. mud (clay + silt)
•
Cosmogenous sediments
– iron-rich particles from outer space, land in the ocean and sink to the bottom
Finding Your Way around the Sea
•
Maps and charts
– Mercator projections
•
Maps and charts
– bathymetric charts
•
Maps and charts
– physiographic charts
•
Reference lines
– latitude
– longitude
•
Reference lines
– divisions of latitude and longitude
•
Navigating the ocean
– principles of navigation
• a sextant was used to determine latitude
• longitude determined using chronometer
– Global Positioning System (GPS)
• utilizes a system of satellites to determine position
• GPS measures the time needed to receive a signal from at least 3 satellites,
and calculates position