CHAPTER 13 A

OCEAN BASINS

P H Y S I CA L S

C I EN C E

Oceans- Vast bodies of salt water that

separate the continents.- They cover about 71% of the earth’s

surface and hold over 97% of all the water on the planet.

- Absorbs sun’s heat, making earth’s climate more uniform compared to other planets

- Home to animal and plant life- -Most of the oxygen in our

atmosphere comes from photosynthetic organisms living in the oceans

- We need to exercise good and wise dominion of the ocean

Scientists who study the ocean• Oceanographers• - marine scientists and engineers who work to better

understand and use the ocean• Marine biologists• -investigate the plant and animal life in the ocean• Meteorologist• - study the influence of the oceans on weather and climate• Chemists• -analyze the distribution of various elements and

compounds in the oceans and the ways those chemicals affect ocean processes

• Physicists• -model the distribution of energy in the oceans and the

motion of its great currents• Marine Engineers• -develop methods and vehicles to investigate and use

oceans, design ways to produce potable water and electricity from seawater. 13.1

Ocean Basins• One ocean• Four major basins• Arctic, Atlantic, Indian,

Pacific • Sea• - large section of ocean

mostly surrounded by land or islands 13.2

Ocean Basins• Origin of the oceans• Old-earth view• - believe that oceans have been here

from very early in Earth’s history, that the ocean basins are just the result of plate tectonics over billions of years.

• -The current Atlantic, Indian & Arctic Ocean basins began forming 300 million years ago

• The Pacific Ocean basin is all that remain from an earlier global sea, Panthalassa 13.3

• Young-earth view• Believe that the earth

began as a water planet, with a single supercontinent created by God on Day 2.

• Supercontinent wrenched apart at Flood around 5500 years ago resulting to the shapes and sizes of the present day ocean basins

• Local sea level• Always changing height of

the ocean surface at a given location

• Measured by Tide gauge• Zero point for gauge

positioned at imaginary surface of mathematical model of the earth called

• Geoid

13.4

• Mean sea level (MSL)• - what most people

simply call “sea level”• -computed average

height of high and low tides at a location

• Zero height used to measure elevation

• Changes over time• Risen during past 100

years 13.4

Basin Topography• Shore• -strip of land that

separates the coastal regions from the ocean.

13.5

• Beaches• -ever-changing place that

extends underwater beyond the shore

• Shoreline• -edge of the water at any

given time.

13.5

• Berm• - area where only the highest

tides or storm waves can reach, usually has soft, coarse sand or large cobbles

• Beach face• - zone between the high and low

tide shorelines; may have wet, compact sand or fine pebbles.

• Longshore sandbar• - shallow bottom of the

beach beyond the low water shoreline

• Longshore trough• - dug by the breaking

action of the waves

13.5

• Continental shelf• Submerged edges of

continental plates• Varies in width

• Continental slope• Steeper incline from the lip

of the continental shelf into the deep ocean basins

• Submarine canyon• -complex underwater erosional

feature often found in continental slope

• Continental rise• Smooth

transition from continental slope to the deep, relatively flat ocean floor

• Turbidity currents

• Underwater landslides 13.5

• Abyssal plain• Relatively

flat, deep sea floor

• Sediments cover it with varying thickness

13.5

Tectonic features• Mid-ocean ridges• Submerged mountain ranges at

the margins of diverging tectonic plates; formed when the mantle pushed up on long faulted sections of sea floor crust. Most lie within fracture zones

13.6

• Seamounts• Submerged volcanoes &

hills• Guyots• Flat top volcanoes

• Trenches• -deep notch in the ocean floor

formed when oceanic plates slid below continental plates in convergent subduction zones

• Challenger Deep –deepest point in any ocean, was found in the Mariana Trench in the western Pacific

13.6

Island arcs- long, curved strings of volcanic island

Coral reefs- Accumulated skeletal material, an underwater ridge,

formed from coral colonies that excrete rock –like calcium carbonate support structure or skeleton; can become islands when sea level changed.

Fringing reefs- Coral reefs that grow right up to the beach along a

coastlineBarrier reefs-farther from the land, form a lagoon between the reef and the landAtoll-a ring of low coral islands and reefs surrounding a central lagoon.