Introduction of Oceanography

Oceanography

General introduction

• The Earth’s surface is divided into major two types: oceanic, with a thin dense crust about 10 km thick, and continental, with a thick light crust about 40 km thick which are also known as first-order relief features.
• The ocean and seas cover 70.8% of the surface of the earth, which amounts approximately to 361,254,000 km2.
• The study of the ocean is oceanography which focuses on the study of physical properties and dynamics of the ocean.
• The average depth of oceans is 3800m
• Hypsographic or hypsometric curve is a technique used for measuring the ocean depth as well as elevation of a relief.

Major Ocean relief features

• Continental shelf
• Continental slope
• Continental rise
• Deep sea plains
• Deep ocean Trench
• Continental shelf
  • The continental shelf extends seaward from the shore with an average gradient of 1 in 500.
  • Average depth of the continental shelf is 200m.
  • Average slope of the continental shelf is 1 degree.
  • It covers approximately 7.5% total ocean cover.
  • Worlds 20% production of crude oil and natural gases are come from continental shelf.
• Continental slope
  • Average slope of continental slope is 2 – 5 degree.
  • Average depth of the continental slope is 3600 – 4000m.
  • It covers approximately 5.5% total ocean cover.
  • The percentage of Continental slope in Atlantic Ocean is 12.4%, in Pacific Ocean 7% and in Indian ocean it is 6.5%.
• Continental Rise
  • The continental rise is slightly sloping between the continental slope and the deep seabed abyssal plain.
  • Average slope is 0.5 – 1 degree.
  • Average depth lies in between 2000 – 3000m.
• Deep sea plain
  • Average depth of Deep sea plain lies between 3000 – 6000m.
  • It covers approximately 75.9% total ocean cover.
  • The percentage of deep sea plain in Pacific Ocean is 80.3%, in Indian ocean 80.1% and in Atlantic Ocean it is 54.9%.
• Ocean Trench
  • Deepest part of the ocean.
  • Generally, trenches are found near to coast line and parallel to the coast.
  •  World’s deepest trench is mariana trench.
  • Normally the ocean trench depth is 5500m.
  • Plate tectonic theory is most relevant theory for expanding the origin of ocean trenches.

Minor Relief features

• Ridges: Mid-oceanic ridges or submarine stripes are underwater mountain systems formed by plate tectonics activities.

• Seamounts: It is a mountain with pointed tops, rising from the beach that does not reach the surface of the sea.
• Guyots: The flat-topped mountains (seamounts) are known as guyots, eg:- Kuko Guyot (estimated 24,600 km2), Suiko Guyot (estimated 20,220 km2), and the Pallada Guyot (estimated 13,680 km²).
• Coral reefs: Coral reefs are formed by small animal colonies found in seawater that contain certain nutrients (calcium carbonate).