GEO-SCI 103 Lecture 3Outline of Last Lecture I. Brief History of Ocean ExplorationII. Latitude and LongitudeIII. Latitude, Climate Zones and the Circumference of the EarthIV. Navigation: Finding Your Way at Sea Outline of Current Lecture: Earth in 2, 3, & 4 Dimensions: maps, structure and historyI. Exploring the Seafloor A. Echo SoundingB. Bathymetric MapsII. Advances in Seafloor ResearchA. Technological AdvancesIII. The Exclusive Economic Zone (EEZ) and the Law of the SeaA. “Freedom of the Seas” (who is entitled to what?)B. Emergence of Regulations IV. History of the EarthA. Creation of the EarthB. Chemical WeatheringC. Excess Volatiles D. Chronology of the Evolution and Formation of EarthV. Correlation of Rock UnitsA. Determining Age without using Radiometric MeasuresCurrent LectureI. Exploring the SeafloorA. Echo Soundinga) Prior to the 20th century, the only means of determining the depth of the ocean was through the method known as sounding.b) Echo SoundingA sound transmitter mounted on the hull of a ship emits high frequency sound waves that travel through the water and are reflected off the seafloor. 1. These returned “echoes” are detected by a device called a hydrophone. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.B. Bathymetry Mapsa) Numerous closely spaced echo sounder profiles can be used to construct a bathymetric map of the seafloor, which refers to the depth of the seafloor below the ocean surface.b) Topography Map the height of the land surface above sea level c) First maps of bathymetry ever made was from wire-line soundings by the Coast Survey Steamer Blake in the Gulf of Mexico during 1874-1875.d) Modern bathymetric maps show the same information, even though soundings can be done much more quicklye) Contour lines (isobaths) connect points that are at equal depths below sea level and provide a way of visualizing three dimensions on a flat piece of paper f) Seismic Reflection ProfilingFurther refinement of the sounding techniques leads to the development of this device. The ship uses a low-frequency sound source such as an air gun that transmits loud “pops” through the water, which can more easily penetrate through thesea floor and show the thickness of buried sediments. 1. These analyses help with determining the origin and evolution of the ocean crust II. Advances in Seafloor ResearchA. Technological Advancesa) Submersibles 1. Give researches the opportunity to dive to great depths in the ocean and observe first-hand and sample features of the ocean bottomb) Remotely-Operated Vehicles (ROVs)1. Sophisticated robotic exploration craft, allowing ocean researchersto explore the sea floor for longer periods of times in less hazardous circumstances. 2. Jason (ROV) is noted for the exploration of the Titanic, but has alsobeen involved in many scientific expeditionsc) Side Scan Sonar1. Advanced echo-sounding technique that sweeps the seafloor with sound waves over a swath up to 100 m wide2. Provides overlapping images and digital technology that produces very detailed images of the seafloor d) Because the ocean is so vast, only a relatively small portion of the seafloor has been mapped with side-scan sonar; to this day we stillknow the bathymetry of the seafloor only as an approximation in many places. III. The Exclusive Economic Zone (EEZ) and Law of the SeaA. “Freedom of the Seas” (who is entitled to what?)a) There are issues that have confronted communities and civilizations from the beginning of their relationship with the sea (who has the right to harvest fish or pump oil from beneath the sea? these are only just a few)b) From early days of seafaring, most countries subscribed to unwritten laws regarding freedom of the seasnations had control over their costal waters 3 miles from the shoreline, but the rest of the ocean was unregulated and open to allB. Emergence of Regulationsa) By the 20th century, the following factors listed below led to inevitable conflicts with entitlement control of the waters:1. Technology2. Human population increases3. Greater demand for fish as food source4. Discovery of valuable economic recourses offshore b) Senate Foreign Relations Committee recommended approval of treaty signed by President Clinton after ratification in 1964. 1. Nations with coastlines have a 12 mile territorial water limit2. There is a further 12 miles in which nations can regulate certain illegal activities such as smuggling or illegal immigrations3. Coastal Nations also have an Exclusive Economic Zone (EEZ) that extends 200 nautical miles from the shorelinec) To help deflect issues of international waters, the Law of the Sea Treaty establishes an International Seabed Authority to monitor the area.d) The Law of the Sea attempts to provide regulation of many commercial activities and to ensure fair use and protection of marine recourses 1. Not an easy task, especially the attempt to have marine recourses shared with nations that do not have a coastline2. Conference established a framework for implementing provisions as international law, but the real test of enforcement and regulatory power of the organization is yet to occur IV. History of the EarthA. Creation of the Planeta) The Earth and other inner planets formed when objects in the early solar system assembled into larger bodies that grew by attracting more and more objectsb) As the Earth reached its present size, it developed layers with the denser materials migrating to the center to form the corec) During initial heating of the planet, extensive volcanic activity released gases from the Earth’s interior that produced an early atmosphere rich in water vapor (H20), Carbon Dioxide and Nitrogend) Water vapor condensed into a liquid, causing torrential rains that ultimately collected in the low spots of the planet to form oceans. B. Chemical Weatheringbreaking down and dissolving of exposed crustal rocksa) Water condensing in the atmosphere in the presence of gasses would reach the Earth with a very low pH, an extreme form of acid rain, which accelerates the process of chemical weathering. b) Elements or substances occur in the atmosphere, ocean and sediments in far greater amounts than can be accounted for by chemical weathering of rocks (see below)C. Excess Volatiles: a) Carbonthe building block of lifeb) Waterc) Chlorinemost common solute in seawater