Chapter 13 – Exploring the Oceans.
Earth is a most unique planet in our solar system in that it has free flowing water on its surface (71%). 4.5 billion years ago, scientists believe that the Earth had no oceans. The surface waters are divided into five main oceans; The Pacific (largest), Atlantic, Indian, Arctic & Antarctic Oceans.
Characteristics of Ocean Water:
It is not safe to drink due to the high salt concentration. Most of the salt is simple table salt, sodium chloride (NaCl). This is an ionic bonding of the elements sodium and chlorine. This is the most abundant dissolved solid found in ocean water. Salts get into the oceans via the weathering of minerals and remain behind when the water evaporates.
Salinity – The amount of salt in ocean water. The salinity of ocean water varies from place to place being lowest along the coastal waters where large rivers empty vast quantities of fresh or non-saline water into areas of humid climates and highest in areas of dry, hot climates and slower moving waters.
1. Surface – sunlight heats up the top 100m. but surface currents mix the water to a depth of up to 300m.
2. Thermocline – Temperature drops off very quickly.
3. Deep – Coldest layer with temperatures around 1 - 3°C.
Surface Temperatures vary with latitude and time of year with the coldest water found at the poles during the winter (1° C) and the warmest in the Middle East in the summer months (36° C).
The Water Cycle – is the continuous exchange of water from the oceans to the atmosphere to the land and back to the oceans. The ocean becomes the single largest source of fresh water through the mechanism of the water cycle.
Thermal Exchange – The oceans absorb and release energy to help regulate the surface temperature of the Earth. Without it, high temperatures would routinely be over 93° C and lows below -129° C (200° F to -200° F).
Continental Shelf – part of the margin that begins at the shoreline.
Continental Slope – the inclined section of the margin.
Continental Rise – found at the base of the slope.
Abyssal Plain – the flat area of the ocean basin that is covered by sediments.
Mid – Ocean Ridges – an underwater chain of mountains that form the single longest mountain range in the world.
Seamounts – individual submarine mountains that could turn into volcanic islands.
Rift Valley – a valley formed between ridges.
Ocean Trench – a deep crack in the basin where the ocean plate is forced (subducted) beneath a continental plate.
Piloted – Alvin& Deep Flight
Robotic –Jason II&Medea
Ocean Life – Marine organisms are grouped by where they live and how they move.
Plankton – plant-like (phytoplankton) and animal-like (zooplankton) organisms that float or drift freely on the surface most of which are microscopic.
Nekton – free swimming organisms that live in the open waters such as whales and dolphins.
Benthos – organisms that live on or in the ocean floor such as oysters and sponges.
Benthic Zone – the bottom environment of the ocean.
Intertidal Zone – the shallow region located between the high and low tide region.
Sublittoral Zone – the area from where the low tide region ends to a depth of 200m. More stable than the intertidal zone because of the more stable temperatures at that depth.
Living (biotic) – plants and animals that we have been harvesting from the ocean for many years. Fish form the largest group and measures have been taken to prevent over-fishing of the oceans in the form of marine law and farms. Kelp is the main seaweed, high in protein, it is harvested as a thickener for use in a variety of products.
Nonliving (abiotic) – resources such as raw materials, drinking water and energy. Oil and natural gas are the two main energy resources harvested and are non renewable.
Desalination – the process that removes salt from seawater producing fresh water in hot, dry climates.
Non-point Source Pollution – Comes from many sources, not just a single site. Most of the ocean’s pollution stemming from human activity (boating, lawn chemicals, etc.) on land and water that works it’s way into the oceans.
Point Source Pollution – Pollution that originates from a single, unique source such as the dumping of garbage from trash barges.
Trash dumped along beaches not only affects the beauty of the beach but is also a health hazard to people and animals.
Tankers are built with double hulls to protect their oil cargo from spilling.
Saving our ocean resources:
In 1989, a treaty was signed by many countries to prevent the dumping of several health hazard wastes into the ocean but the dumping still continues. Many citizens across the world are forming volunteer groups to clean up the beaches such as the “Adopt a Beach” program.