OSU OC 103 - e-OC103_Lesson02-2 (9 pages)

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e-OC103_Lesson02-2

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9
School:
Oregon State University
Course:
Oc 103 - Exploring The Deep: Geography Of The World's Oceans
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OC103 Lesson 2 Ocean Exploration in the Past Development of a Science Historical Review of Oceanography The roots of oceanography can be traced to ocean exploration by ancient civilizations Whether it was the early Polynesians in open canoes exploring the South Pacific for new island homes see shaded area of the Pacific Ocean in the figure below or Egyptians exploring their coastline for new fishing grounds and trade routes the earliest explorers had to be able to chart their courses using the stars and landmarks a process known as piloting They also used dead reckoning which relies on guessing your heading and speed over the course of hours or days Knowledge of ocean currents and prevailing winds are crucial to accurate dead reckoning so early sailors started the tradition of keeping detailed records of oceanic and atmospheric conditions during their travels They could therefore be considered the first oceanographers The fact was in the early days sailors who had been out of sight of land for more than a few days often did not know where they were Sure their compass told them what direction they were heading and they could make a pretty accurate guess at how fast they were sailing through the water but what if they were sailing through a strong current They could be miles off in their dead reckoning for each day s progress and that error would accumulate day after day After a month at sea they could be hundreds of miles from where they thought they were Knowledge about the oceans continued to accumulate over the years but it was not until the 18th century that some major advances took place in ocean navigation and mapping The Longitude problem A key event that made detailed oceanography possible was the invention of a clock that worked on a ship As odd as it sounds without an accurate clock it was very difficult for sailors out on the open ocean to determine where they were It was fairly simple to determine latitude north south distance from the equator by taking a careful sighting of the sun or certain stars but determining longitude east west distance from some standard location usually Greenwich England required taking a sighting of the sun AND knowing exactly what time it was in Greenwich England at the moment you took your sun sighting This required having a clock on your ship that kept accurate time for weeks or months at sea Until the mid 18th century all clocks used some variation of a swinging pendulum to keep time but the rocking motion of a ship disrupts a pendulum s motion rendering these clocks inaccurate As sailing vessels ventured farther and farther from home this became more and more of a problem In 1714 the British government offered a reward for whoever could design a clock that would allow sailors to accurately determine their longitude at sea The problem was not solved until about 20 years later when John Harrison finally invented a clock that kept accurate time at sea Until Harrison s clock made it possible to determine a ship s longitude a captain headed for a remote island usually had to take an indirect route by sailing north or south until he reached the island s latitude and then sailing along that line of latitude until he reached the island hopefully in the daylight when they could see it in time and hopefully avoiding the pirates that hung around the latitude lines that they knew ships had to follow A direct route would have been much shorter and faster but if they aimed for the island from the beginning and could not see it when they got to the correct latitude they would not know their longitude so would not know if they needed to go east or west to find the island So the direct routes made possible by Harrison s clock led to considerable time savings for ocean journeys Harrison s first seagoing clock built in 1735 Accumulation of data for charts and exploration With the new found ability to know exactly where they were at almost all times sailors were now able to make repeated observations of ocean conditions over the course of their travels Accurately located information about ocean currents water temperatures and prevailing winds could now be accumulated and recorded A good example of how this accumulated oceanographic knowledge proved useful comes from an oceanographic chart created by Benjamin Franklin yes that Ben Franklin After several diplomatic journeys between the U S and Europe during the time just before America declared independence from England Ben Franklin noticed that experienced sailors departing the East Coast of America would ride a current of warm water northward and eastward to speed their journey to Europe And on the return trip to America they would intentionally sail southward first before turning west to avoid fighting this warm current on their way back to America In 1770 Franklin published the first chart showing how the course of this warm current called the Gulf Stream flowed northward along the East Coast of America before turning eastward toward Europe see figure below The Voyages of Captain James Cook Around this same time that Ben Franklin was shuttling back and forth across the North Atlantic 1768 1779 a British Captain James Cook was exploring the world s oceans He searched unsuccessfully due to ice and fog for a great southern continent Although Cook never saw Antarctica he was able to establish that if it existed it was too far south to be habitable It would be nearly 50 years before someone finally got close enough to Antarctica in clear enough weather to actually lay eyes on it Cook constructed charts of the coastlines of western North America including Oregon Washington and Alaska but mostly avoided California because that area was claimed by Spain and islands in the South Pacific including Hawaii and New Zealand Although Cook s voyages had scientists and naturalists on board their purposes were primarily nationalistic not scientific The British government was more concerned with surveying and solidifying its existing territorial claims as well as claiming new lands and surveying for valuable resources such as whales and seals for blubber and oil wood for shipbuilding and repair you can imagine how excited Cook was to see the huge straight trees growing along the coast of Oregon and convenient sources of freshwater along the coasts to replenish the drinking water supplies of passing ships The voyages of Capt Cook 1768 71 in red 1772 75 in green and 1776 80 in blue dashed where his ship returned to England


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