1_Oceanography (Introduction)

Overview of Planet Earth

  • Planet Earth is largely covered by water, with 71% of its surface being water and 29% land.

  • If all Earth’s water was condensed into a bubble, it would measure only 1,385 kilometers in diameter, highlighting the vastness of the planet.

Land Surface Composition

  • The land on Earth includes mountains, plateaus, and plains, with coastal plains extending as ocean floors.

Ocean Floor Divisions

Major Divisions

  • Continental Shelf:

    • An underwater landmass extending from continents, characterized by relatively shallow waters (30 meters to 600 meters deep).

    • The average width is about 80 kilometers, with variations; notably, the Siberian shelf in the Arctic Ocean is the largest at 1,500 kilometers wide.

  • Continental Slope:

    • Connects continental shelf to ocean basin; depth ranges from 200-3,000 meters, marked by a steep drop-off known as the shelf break.

  • Deep Sea Plains:

    • These are the flattest areas of the ocean basin, reaching depths up to 9,000 meters and covered with fine sediments like clay and silt.

  • Oceanic Deeps:

    • The deepest ocean sections, significant for plate tectonics due to associations with volcanoes and earthquakes.

Relief Features

  • Major and minor features include ridges, hills, seamounts, guyots, trenches, and canyons.

Coastal Regions

Littoral Zone

  • The littoral zone comprises regions close to shore, from the high water mark to submerged areas.

    • Subregions include:

      • Supralittoral Zone: Above the spring high tide line; regularly splashed but not submerged.

      • Eulittoral Zone (Intertidal Zone): Between high and low tide lines, regularly exposed and submerged.

      • Sublittoral Zone: Located below the eulittoral zone, remains submerged and aligns with the neritic zone around the continental shelf.

Pelagic Zone

  • The pelagic zone includes the water column in the open ocean, extending through various regions:

    • Epipelagic Zone: Surface to 200 meters, receives sunlight, allowing photosynthesis; known as the sunlight zone.

    • Mesopelagic Zone: Ranges from 200 to 1,000 meters; referred to as the twilight zone, home to bioluminescent organisms.

    • Bathypelagic Zone: Extends from 1,000 to 4,000 meters, characterized by immense pressure and dark conditions.

    • Abyssopelagic Zone: Encompasses depths over 4,000 meters, home to few species adapted to extreme conditions.

Oceanic Trenches and the Hadal Zone

  • Oceanic trenches are the deepest parts of the ocean, 3-5 kilometers deeper than the surrounding floor, significant for geological studies.

  • Key trenches include: Mariana Trench, Peru-Chile Trench, and Japan Trench.

  • The hadal zone encompasses extreme depths, characterized by high pressure and darkness, with few species, but hydrothermal vents support diverse life forms.

    • Hydrothermal vents release heated water and gases, hosting unique organisms like tube worms and clams.