ACE Class Report – Oceanography 1.
Title: Oceanography: Exploring Earth’s Final Wilderness.
Instructor: Professor Harold J. Tobin
University of Wisconsin – Madison
Why I choose to Take This Class:
Oceanography weaves together Geology, Biology, Physics and Chemistry to illuminate the single ocean – vast, deep and mostly dark. This class gives me the opportunity to explore the ocean and understand the mystery of what lies beneath the surface of the waves.
What I learned from this Class:
Diving In- The Ocean Adventure:
71% of the earth is covered by ocean. Seawater and saltwater compose 97% of earth’s surface water. All the freshwater; polar Icecaps, lakes, rivers, stream and ponds and ground water that supplies our drinking water composed only 3% of the water on the planet. For nearly all of the 4.5 billion years history of the planet, the ocean has also been around. The Ocean has been essential to life; to the climate, that makes earth a habitable environment; and even to the geological forces of the planet.
Explorers, Navigator, Pioneering scientist:
Ocean exploration developed early technologies of shipbuilding and navigation, mostly as a by product of practical needs. Open ocean crossing by Polynesian, Nordic and European seafarer were accomplished through remarkably skilled navigation.
Chronometer – Precise clock originally used to determine longitude based on timing of local noon.
Sextant – Instrument used to measure the angle above the horizon of celestial objects that is used in navigation.
Stick Chart – Map like representation of islands, waves,and ocean current used in navigation by Micronesian and Polynesian seafarers.
Ocean Basics and Ocean Basins:
The ocean basins have their own unique physiographic features reflecting the geological origin. Major features include globe-encircling mid-ocean ridge mountain range; dep sea trenches, vast abyssal plains; and the continental shelves, slopes and rises. Each major ocean basin – Pacific, Atlantic, Artic, Indian has unique architecture, reflecting common processes but differing histories. The deep-ocean floor is underlain by oceanic crust, which is formed exclusively by volcanic processes and is completely different from the continental crust.
Mapping the sea – Soundings to Satellites:
Major basic features of the ocean floor were completely unknown until the late 19th century. Features as large as undersea mountains are still being discovered today through the progression of methods from line and weight sounding to acoustic echo sounding and sonar mapping to satellite altimetry. Modern oceanographic instruments digitally record currents, temperature, pressure, and salinity all over the world, mapping out the water itself.
Bathymetry – The measurement of the depth below sea level, is an inverse mirror of the topography on land.
Habitats – Sunlit Shelves to the Dark Abyss:
Just as on land, life in the ocean depends on habitat. Key ingredients for living organisms are: light, nutrients, temperature, pressure, chemistry and substrate. The geomorphology of the sea floor governs Benthic habitats from the Littoral zone to the Abyssal zone, wide, Sunlit Continental shelves host the most abundant life. Deep and completely dark Continental Slopes and Abyssal plains host a sur[prizing diversity and abundance of life too. Special environment host entire ecosystems not based on the sun’s energy but rather on plate tectonic energy from earth.
The shallow zone that is sunlit is called the Photic zone. By contrast everything below the photic zone is called the Aphotic.
Zone – the zone without any light.
The Spreading Sea Floor and Mid Ocean Ridges:
Plate Tectonic explains the the ocean basins are different from the continents because they form through seafloor spreading at the mid ocean ridges. Mapping of the mid Atlantic Ridge contemporaneously with the development of radioactive decay dating of Rocks and or rock magnetism led by Harry Hess and others to propose seafloor spreading in the 1960s. Alternating stripes of magnetized rocks due to earth’s magnetic reversals through time added support to the theory. Crust get older symmetrically on either side of the ridge, and ocean basin rocks are geologically very young in relation to the continents.
The Plunging Sea Floor and Deep Sea Trenches:
Ocean-Floor crust is created at the ridges, so it must be consumed elsewhere; subduction zones at deep sea trenches are the locations where ocean floor is recycled back into earth’s mantle,and transform faults link up the ridges and trenches, completing the plate Tectonic system. Subduction zones are the sites of the greatest earthquakes and Tsunami. Oceanic trenches as deep as 11,000 meters are the product of plate subduction. The plate Tectonic cycle is one of constant destruction, renewal, and reconfiguration of ocean basins, but the continents remain mostly intact.
The Formation Of The Earth and Its Ocean:
As the solar system formed, earth uniquely had the right conditions and ingredients for liquid water on the surface, and it has had an ocean for 4 billion years. Water was present from the initial accretion of the planet and separated from rock early in earth’s history; comets nay have added more water as well. the early earth was too hot for oceans to from, but gradual cooling took place through 25 million years of steady rain. Th moon formed through the collision of Mars sized body with the early earth.
The Early Ocean and The Origins Of Life:
Over the first 2/3 of the earth’s history, the ocean atmosphere,and the rocky surface changed from an early oxygen-poor state to the present oxygen rich system, and the development of life and photosynthesis dominates these changes. Early atmosphere had no oxygen but gradually changed to its present composition due to photosynthesis in the ocean. Liquid water is the most essential ingredient for life on earth; the ocean provided the only stable environment over the eons of early evolution.
Marine Sediments-Archives Of The Ocean:
After the ocean floor was created, sediments accumulated on it in layers that can be interpreted into a history of the ocean and climate through time. Marine sediments preserve clues to the environment at the time of their deposition in the type of fossils, the nature of grains of sand, and the chemical fingerprint of past climate. Many of the rock formations we see on land began as marine sediments and were incorporated into the continents through plate tectonic processes.
Offshore Oil And Gas – Resources and Risks:
Marine sediments are the source and host of all oil and gas deposits, the legacy of millions of years of life in the sea. The development of offshore oil brings societal needs and environmental and aesthetic concerns into conflict. The scale of the offshore drilling and production industry is immense, with billions of dollars invested in even a single platform. Smaller scale resources extraction from the sea include minerals, especially salt, and energy extraction through tide generators or thermal energy conversion.
The Enduring Chemistry of Seawater:
The unique and surprising properties of H2O, the water molecule, are responsible for the existence of a liquid ocean and a benign and relatively stable environment for life on earth. Water is the only common substance that exist in gaseous, liquid and solid form on the surface of earth. The incredible heat-retaining capacity of liquid water has acted as a global thermostat through geologic time. Light penetrates only about 200 meters into the ocean – The photic zone – which controls the habitat.
How will this class contribute to my success upon release:
Topics like oceanography improves my knowledge about the environment an its contribution to civilization. This knowledge will improve my critical thinking skills. The knowledge acquired will be taught to the communities which I volunteer my services.