Intro:
3/4ths of the earth’s surface is covered with water. The
ocean contains 97% of all the earth’s water. The mass of
the ocean is 1/400th of the earth as a whole. The volume is 1/800th
of the earth as a whole.
Ocean Divisions :
Divide the earth’s oceans into 3 parts:
1-Pacific Ocean (which includes the Antarctic Ocean)
2-Atlantic Ocean (which includes the Arctic Ocean)
3- Indian Ocean
Sea is a term that applies to areas of the world oceans that are
partially surrounded by land
-Each of these oceans differ in either size, depth, or salinity.
Oceanography: study of the physical, chemical, and biological
characteristics of the oceans.
Tools: surface vessels, submersibles, and Sonar.
Ocean Basin features :
Divide the Ocean Basin into 3 general areas:
1) Continental Margins- portion of the basin composed of continental
crust.
Sub-Divide this feature into the:
a. flat, gentle sloping- Continental Shelf
1. exposed periodically to W & E during the Ice Age periods
2. a smoother version of the land surface
b. at the edge of the shelf is a steeper slope- Continental Slope
Both the continental shelf and slope can be cut by deep v-shaped
valleys. In the C. slope these valleys are called submarine canyons
They are thought to form from Turbidity currents that cause underwater
landslides that act as powerful agents of erosion.
Material deposited at the base of the slope may be enough to form a continental rise.
Some slopes are very steep and plunge down into trenches.
2) Ocean Floor: is composed of oceanic crust. The ocean floor
has many varied and distinct features:
a. Abyssal Plains-cover half of the ocean floor; very flat, devoid
of life; heavy deposits of sediment; found primarily where
there is few trenches (Atlantic Ocean)
b. Seamounts: submerged volcanic mountains (some emerge form islands)
c. Guyots- flat topped seamounts- results when islands are eroded
by waves, they are “pulled down” when the ocean floor
sinks (remember plate tectonic theory!)
3) Mid-Ocean Ridges: Again remember plate tectonic theory! Each MOR has an associated rift running along its center.
Basin Sediments:
Ocean floor sediments are quite varied due to the different sources.
Samples of sediment taken near the continental shelf will be different
then samples taken from the abyssal plain.
Sources of Sediment:
1) Inorganic sediments- rock particles carried from land by rivers.
Most of these are found on the shelf, however, they can be moved
down to the floor by great landslides (see turbidity currents).
Other sources besides rivers are: icebergs, volcanic eruptions,
and meteors.
2) Organic Sediments- remains of living things. The most common substances in organic sediments are silica (from diatoms) and calcium carbonate (from foraminifera) and the remains of corals and bivalves.
3) Chemical Deposits- sediments that are formed from chemical reactions that occur in the ocean. May form lumps of minerals called nodules.
Classify Sediments by physical characteristics:
Muds: very fine particles of rock. most common is red clay
Ooze: soft organic sediment. ex. Calcareous and siliceous.