Margins and Basins

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Unit 5

• Margins and Basins

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Mapping The Globe

• Latitude
• Longitude
• Equator

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Latitude

• Angular distance from any point from equator,
• measured north or south.
• Measured in degrees, minutes and seconds.
• Each minute one nautical mile (1.15 mi or 1.85
  km)

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Longitude

• Angle between meridian and standard meridian
  (Greenwich, England)
• At equator, one degree of longitude is about 70
  mi or 113km.

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Why Greenwich?

• Zero line of longitude

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Magellans Routes
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History of Exploration

• Phoenicians- 2000BC
• Aristotle- 4th century BC- first to recognize
  gills as breathing apparatus (1st marine
  biologist)
• Vikings- N. Atlantic, 9th century
• Portuguese- India, 15th century
• Columbus- Atlantic, 15th century

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James Cook- Antarctica, and Pacific Islands 18th
century

• First to make scientific observations
• Had a naturalist on board
• Three voyages- explored all the oceans
• Discovered New Zealand, then Australia
• Calculated longitude and prepared sea charts
• Brought back specimens of plants and animals
• Started Australian beer industry!
• Killed by native Hawaiians- Kealakekua Bay over a
  stolen boat

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Cooks Endeavour
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James Cook and a letter requesting additional
supplies for an extended voyage
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Cooks voyages
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Darwin- the most famous naturalist

• HMS Beagle
• Collected plankton in nets
• Proposed explanation for the formation of an
  atoll reef
• Studied barnacles

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Challenger 1872

• Sea floor dredging
• Three year voyage- gathering info and collecting
  samples
• 19 years to publish the results

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Challengers route
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All the world is discovered

• This opened the world to avenues of commerce, war
  and disease.
• Immigrants, slaves, religions, products and ideas
  were transported around the world
• Today- crude oil accounts for the largest object
  of trade

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Alvin before it descends to Titanic
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Life at the Bottom

• Deep Sea Mysteries MMCD 3

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Echosounders- a useful tool
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Oceans and Continents

• Ocean Basins- four major ocean basins
• Arctic
• Atlantic
• Indian
• Pacific
• Seas- term is not used consistently
• Enclosed lakes (Caspian or Galilee)
• Partially enclosed or isolated ocean sections
  (Med)
• Seven seas refers to the oceans
• South seas used in literature

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Dividing the Waters- vertically

• Surface- photosynthetic organisms
• 71 of the earths surface is water
• 80 of the Southern Hemisphere is water
• Continental Shelf
• Slope
• Rise
• Pelagic- open ocean
• Ocean Basin

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Oceanic crust- Table 2.2 p.24

• More dense than land crust
• Much younger geologically- 200 million years
  old
• Made up of basalt (rather than granite)
• Only 3 miles (5km) thick
• Dark in color
• Rich in iron and magnesium

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Oceanic crust

• More dense than land crust
• Much younger geologically- 200 million years
  old
• Made up of basalt (rather than granite)
• Only 3 miles (5km) thick
• Dark in color
• Rich in iron and magnesium

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Mapping the Ocean Floor

• MM CD 3
• 3-D Mapping of Ocean Floor

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First hand-drawn map of seafloor (tip of S.
America)
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Comparing heights- ground to under water
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The Sea Floor Basin
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Fig. 4.15 on page 97
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The ridge system
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Mid-Ocean Ridge

• Chain of volcanic submarine mountains
• Displaced by transform faults
• Rise above sea level to form islands (Iceland)
• Mid- Atlantic Ridge- right down the middle
• Trenches- deep depressions (common in Pacific)

Krafla Volcano- Iceland
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• Earthquakes at the Ridge
• Volcanoes at the trenches
• Sea floor spreading- rifts created as the crust
  separates at the ridges.

Ridge- Iceland
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Underwater Civilization

• Deep Sea Mysteries MMCD 4

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Smokers
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Ocean Trenches
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Typical Continental margins
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