Oceanography

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Colossal Squid (Mesonychoteuthis hamiltoni)
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12 – 14 m long…..(39-46 ft) (think Olympic size swimming pool)
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ocean acidification
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is the ongoing decrease in the pH of the Earth’s oceans, caused by the uptake of carbon dioxide (CO 2) from the atmosphere. An estimated 30-40% of the carbon dioxide released by humans into the atmosphere dissolves into oceans, rivers and lakes.[3][4] To achieve chemical equilibrium, some of it reacts with the water to form carbonic acid.
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First people to explore the ocean
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30,000 years ago – Polynesian Seafarers started migrating across the Pacific.
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Hokule’a
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a traditional Polynesian canoe
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Malama Honua
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the polynesian voyaging canoes are sailing across the Earth’s oceans to join the global movement towards a more sustainable world (started in 2013)
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colonization of western pacific islands by the Polyneasians
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– there are 10,000 islands in the western Pacific -Colonized New Guinea (30,000 years ago) -Colonized Philippines (20,000 years ago) -Colonized Hawaii (farthest away away from any land masses)- 1,500 years ago -easter Island- around 1200 A.D. -from genetic evididence
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Easter Islands
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polynesians created a thriving culture in the first millennium but overpopulation eventually led to the gradual deforestation and extinction of natural resources which caused the demise of the Rapa Nui civilization
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methods of early navigation
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-reflection of islands in the clouds -followed birds (Frigate and terns- dawn and dusk patterns) -stars -swells -stick charts -smell of the water
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Kon-Tiki by Thor Heyerdahl
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Theory- could Polynesia have been colonized by trans-Pacific emigres from the pre-Colombian cultures of South America? Heyerdahl gathered five friends and set sail from Peru across the Pacific to Tuamotus, French Polynesia Kon-Tiki demonstrated that it was possible for a primitive raft to sail the Pacific with relative ease and safety, especially to the west (with the trade winds).Sailors could have survived by fishing. Blood samples taken proved Heyerdahl’s hypothesis but scientists argued contamination. The South American Sweet potato was part of a dietary supplement in Polynesia
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900-700 B.C. Greeks
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had traveled inside the Mediterranean but not outside of it
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phytoplankton
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are photosynthesizing microscopic organisms (account for half of the photosynthetic activity on earth) that inhabit the upper sunlit layer of almost all oceans and bodies of fresh water and are a key factor of oceans, seas and freshwater basins ecosystems. They are agents for “primary production,” the creation of organic compounds from carbon dioxide dissolved in the water
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Trichodesmium
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also called sea sawdust. Fixes atmospheric nitrogen into ammonium
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Gokstad Ship
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a viking ship intended for warfare, trade, transportation of people and cargo. Was used during the period that the Vikings expanded into Dublin, Ireland and York, England at the end of the 9th century
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860 AD voyage
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first Viking voyage to iceland
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981 AD voyage
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Erik the Red… sailed west from Iceland and discovered Greenland.
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985 AD voyage
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Bjarni Herjolfsson – missed Greenland – is thought to be the first to see New Foundland. He is believed to be the first to see North America.
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995 AD voyage
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Leif Eriksson -son of Erik the red – set out to find New Foundland – and did – he named it Vinland because of the grapes…. But the Vikings left Greenland and Vinland – and were gone by around 1450.
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Viking Colonies
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were in Iceland and the south of Greenland but were gone by around 1450
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Farthest known extent of European exploration before Columbus (Vikings)
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-first viking voyage to Iceland -Erik the Red discovered Greenland -Bjarni Herjolfsson- first to see North America (Vinland) Leif Eriksson- found North America (Vinland)
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Zheng He
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was a navigator that lived from 1371 to 1433. had 48 to 317 ships and 28,000 crew members. He commanded expeditionary voyages to Southeast Asia, South Asia, the Middle East, and East Africa from 1405 to 1433. He demonstrated the power and wealth of the Ming Dynasty- he spread the glory of China to the countries he visited. When a new emperor took the throne- he criticized Zheng and the sea voyages were abandoned. Zheng took seven voyages in his life time
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Navigators
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-Zheng He (1405-1433), hundreds of ships and thousands of crew members -Columbus (1492), 3 ships and 90 crew members (america) -Da Gama (1498), 4 ships and 160 crew members (india) Magellan (1521), 5 ships nad 265 crew members (the first circumnavigation of the Earth)
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Captain James Cook (1728-1779)
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was a British explorer, navigator, cartographer, and captain in the Royal Navy. Cook made detailed maps of Newfoundland prior to making three voyages to the Pacific Ocean, during which he achieved the first recorded European contact with the eastern coastline of Australia and the Hawaiian Islands, and the first recorded circumnavigation of New Zealand.
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James Cook’s Three expeditions
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-endeavor -resolution -adventure
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James Cook first voyage (endeavor)
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(1768-1771) Sailed from England westward across the Pacific to Tahiti, where the observations of Venus Transit were made. Mapped the entire coastlines of New Zealand. He then searched the South Pacific for signs of the postulated rich southern continent of Australia.- found dark skinned people and unique . Chartered the entire continent of Australia. (first Europeans to do so)
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Oservations of Venus Transit
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During a transit, Venus appears as a small black disc traveling across the Sun. It takes place in a pattern that repeats itself every 243 years. It includes two transits that are 8 years apart. There are four phases, first is Venus touching outside rim of sun, second is Venus within the sun’s disc, third Venus crossed the sun, and the fourth is Venus completely off the sun but still touching the outer rim. Observers had trouble recording the exact times of the different stages because of a haze.
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James Cook’s second voyage- Resolution
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(1772) The Royal Society still believed there was a massive southern continent that should exist. Cook’s expedition circumnavigated the globe at an extreme southern latitude, becoming one of the first to cross the Antarctic Circle. His reports upon his return home put to rest the popular myth of Terra Australis. This voyage marked the successful use of the marine chronometer(calculated longitudinal position). Did not lose any men on this voyage.
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James Cook’s third voyage- Adventure
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led the public to believe the voyage was planned to return the pacific islander to Tahiti but were actually to locate a Northwest Passage to the American Continent. Cook became the first European to begin formal contact with the Hawaiian Islands (named them the sandwich islands). He then accidentally sailed towards Canada and anchored at Yuquot. He then went on to identify what became known as the Cook Inlet- 180 mile body of water on the gulf of Alaska. Cook charted the majority of the North American north-west coastline on world maps for the first time, determined the extent of Alaska, and closed the gaps in Russian (from the West) and Spanish (from the South) exploratory probes of the Northern limits of the Pacific.
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The Cook Expedition Findings
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-extensive scientific investigations -arctic to antarctic -mapping of the pacific ocean -depth soundings -winds and currents -subsurface temperature -biological sampling -general geography of the world
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scurvy symptons
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-loss of teeth -sunken eyes -pale skin caused by deficiency of vitamin C
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Captain Cook and Scurvy
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– Cook had 5 cases of scurvy -he made sure his crew members had sufficient vitamins and prevented them from getting scurvy
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HMS Beagle
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constructed in 1820 for the Royal Navy. Took part in the fleet celebrating the coronation of King George IV of the UK. First ship to sale under the London Bridge.
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HMS Beagle first voyage
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(1826-1830) captain fell into depression and killed himself. Replaced by Lieutenant W.G. and sailed to Montevido. Beagle Channel was identified (a strait in South America)
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HMS Beagle second voyage
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(18310 1836) There were many difficulties and delays which led to Charles Darwin joining the voyage. Darwin kept a diary of his experiences and rewrote it as a book called Journal and Remarks which was renamed to be the Voyage of the Beagle
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The Voyage of the Beagle by Charles Darwin
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is illustrating his changing views at a time when he was developing his theory of evolution by natural selection and includes some suggestions of his ideas
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HMS Beagle third voyage
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(1837 to 1843) set off to survey large parts of the coast of Australia. The Beagle Gulf was found
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Lt. Matthew Maury
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-Head of the U.S. Navy’s Depot of Charts and Instruments. -1847-assembled the observations archived there into charts of winds, currents, and sea state throughout the trade routes. -1855-Author of the first oceanography textbook The Physical Geography of the Sea. -Father of Physical Oceanography -Probably, the first person to devote full time to the study of the ocean.
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the first oceanography textbook
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by Lt. Matthew Maury named The Physical Geography of the Sea
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the challenger expedition
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-Lead by Charles Wyville Thompson – Departed on December 7, 1872 -was a scientific exercise that made many discoveries to lay the foundation of oceanography -catalogued over 4,000 previously unknown species -traveled nearly 70k miles -sampled in the North and South Atlantic and Pacific Oceans -Travelled north of the limits of drift ice in the North Atlantic polar seas and south of the Antarctic Circle -measured the depths of the Marianas Trench (deepest part of the worlds oceans) in the western Pacific (26,850 feet) -atmospheric and other meteorological conditions were carefully observed and noted. The direction and rate of the surface current was determined. -major motivation- – is there life at depth?
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Wyville Thomson on sampling
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the Challenger made 362 sample/observation stations “at intervals as nearly uniform as possible
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At intervals, the Challenger crew would
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1. measure depth 2. sample of the bottom 3. A sample of bottom water for chemical/physical examination 4. recorded bottom temperature
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At most station, the Challenger crew would
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– a fair sample of the bottom animal life (fauna) (dredge or trawl) -the animal life of the surface and of intermediate depths (tow nets). -a series of temperature observations was made at different depths
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At many station, the Challenger crew would
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samples of sea-water samples at different depths.
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Edward Forbes
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-he pursued the study of life in the littoral zones (the ocean from the shore to the continental shelf) and developed an interest in the geographical distribution of animals. -known for azoic theory
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azoic theory
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no life in the deep ocean (>550 m)
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Dispelled the Azoics Theory
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the challenger expedition disproved this theory -133 dredges taken -4700 new species discovered
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Fridtjof Nansen
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– tested the possibility of reaching the North Pole by using the natural drift of Polar Ice (Fram’s expedition) -first to cross Greenland’s inland ice, failed to reach the north pole
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Routes taken on Fram’s expedition (1893-1896)
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-eastward from Vardo along the Siberian coast, turning north at the New Siberian Islands to enter the pack ice -drift in the ice from the New Siberian Island North and West to Spitsbergen -March farthest North and then retreat to Cape Flora -Return to Vardo form Cape Flora -voyage from Spitsbergen to Tromso
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Woods Hole – US Fish Commission – 1871
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-beginning growth of marine research -in cape cod – a number of eminent scientists brought to Woods Hole -the federal government realized that marine populations needed to be studied and managed to protect fishing stocks and the markets that depended on them
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The Bathysphere
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– was a unique spherical deep-sea submersible which was unpowered and lowered into the ocean on a cable, and was used to conduct a series of dives off the coast of Bermuda from 1930 to 1934. -designed by William Beebe & Otis Barton
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The Trieste
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(1960) a Swiss-designed, Italian-built deep-diving research bathyscaphe,the first manned vessel to have reached the bottom of the Challenger Deep. (roughly 7 miles beneath the ocean surface) -Piccard and Walsh of the US Navy reached the goals of project Nekton
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Six elements are the major constituents of living tissue and they account for 95% of the biosphere…
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CHONPS -carbon -hydrogen -oxygen -nitrogen -phosphorus -sulfur
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biosphere
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-Zone of Life on Earth -Global Sum of all ecosystems
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ecosystems
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Biotic/Abiotic (i.e. – the living/non living) components of a system….
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Atomic Number
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number of protons
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Atomic Weight:
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average mass of atoms of an element, calculated using the relative abundance of isotopes in a naturally occurring element.
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Isotope:
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Atoms with the same number of protons but different number of neutrons. ex. Carbon-12 = 6 protons + 6 neutrons Carbon-14 = 6 protons + 8 neutrons
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the big bang occured
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13.7 billion years ago
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seconds after the big bang
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Hydrogen and Helium began to form
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big bang nucleosynthesis
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H and He forming seconds after Big Bang
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Stellar Nucleosynthesis
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one billion years after the big bang- stars formed and with them other heavier elements – increase temperature and pressure caused heavier elements to form
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How many stars are there?
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in the milky way we think there are 200-400 billion but there might be 3000 galaxies
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the nebular hypothesis
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-explains formation and evolution of the solar system -a nebula contracts under gravity and heats, flattens and spins faster, becoming a spinning disk of dust and gas -stars form in the center of the disk and planets form on the outer parts of the disk -H and He remain gaseous but other material can condense into solid “seeds” for building planets -warm temperatures allow only metal/rock “seeds” to condense in the inner solar system -cold temperatures allow “seeds” to contain abundant ice outer solar system Formation of Protoplanets -solid seeds collide and stick together -larger seeds attract others with gravity, growing bigger still -terrestrial planets are built from metal and rock – the seeds of gas giant planets grow large enough to attract hydrogen and hellium gas, making them into giant, mostly gaseous planets, moons form in disks of dust and gas that surround the planets Our Solar System -terrestrial planets remain in the inner solar system -gas planets remain in the outer parts -“leftovers” from this process become asteroids (metal/rock) and comets (mostly ice)
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nebula
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(large, diffuse gas cloud of gas and dust)
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age of the earth
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4.57 billion years old
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Meteorites
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-give us access to debris left over from the formation of the solar system -can determine the age using using radioactive isotopes and their decay products
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Geological time of earth
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-sun formed -moon formed -earths core grows and differentiation completed -oldest mineral grain and continental rocks -earliest evidence of liquid water -earliest evidence of life -major phase of continent formation complete -build up of oxygen -ice covered earth -big bang -mass extinction -earliest land animals -mass extinction -earliest flowering plants -mass extinction -first hominids -first appearance of our species
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3 major factors that caused heating and melting in the early Earth’s interior:
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-collisions -compression -radioactivity of elements (e.g. uranium, potassium, or thorium)
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collisions
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(Transfer of kinetic energy into heat)
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About 100 million years after initial accretion of the earth
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temperatures at depths of 400 to 800 km below the Earth’s surface reach the melting point of iron
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During this time (temperatures below earth’s surfaces reach the melting point of iron)
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the heavier elements, including the melted iron, began to sink down into the core of the Earth, while the lighter elements such as oxygen and silica floated up towards the surface- density stratification and crust forms
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What is density ?
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Mass per unit volume
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Density stratification
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describes the layers of water in a body of water with a layer of cold dense water at the bottom and, at temperatures above freezing, a warmer layer floating on top.
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density of water
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1.00 g cm-3
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density of gold
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19.30
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Global Chemical Differentiation
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Chemical seperation was completed by about 4.3 billion years ago, and the Earth had developed a inner and outer core, a mantle and crust
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density in order- lightest to heaviest
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-water -glass -lead -mercury -gold
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earth composition general
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-solid iron inner core -liquid iron outer core -mantle -crust on the outside
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Chemical Composition of Earth
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Each of the major layers has a distinctive chemical composition, with the crust being quite different from the Earth as a whole
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whole earth’s composition
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iron (35%) Oxygen (30%) Silicon (15%) Magnesium (13%) Nickel, sulfur, calcium, aluminum, other
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earth’s crust composition
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oxygen (46%) silicon (28%) aluminum (8%) Iron (6%) magnesium (4%) calcium,potassium, sodium, other
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Proto-earth (4.5 billion years ago)
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The sky above a still-forming proto-Earth is filled with the dust, rocks and gas that are shaping our solar system. A rising proto-sun illuminates the dust and rocks that gravity brings hurtling toward this new planet. The first comets, scattered by the gravity of the giant outer planets, appear in our sky.
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early earth (4 to 4.5 billion years ago)
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Our recently formed moon rises in the night sky. Not in its final orbit yet, the moon is seen much larger in the sky than than today’s moon. Magma flow from mare volcanism can be seen on its surface. Three comets, or water-rich asteroids, begin their descent into Earth, delivering with them a supply of frozen water
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The Giant Impact Hypothesis
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-50 million years after the initial creation of Earth, a planet about the size of Mars collided with Earth to create the moon. This idea was first proposed about 30 years ago, but it took calculations by modern high-speed computers to prove the feasibility
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evidence of The Giant Impact Hypothesis
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1. moon rock is younger than other celestial bodies (~ 30-55 million years) – 2. similar composition to earth – 3. moon is less dense than earth and other planets…..
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Origin of Earth’s atmosphere
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Partial melting resulted in outgassing about 4 billion years ago – Similar to gases emitted from volcanoes – Mainly water vapor – Carbon dioxide, hydrogen – Other gases such as methane and ammonia
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Where did the Ocean come from ?
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-two sources of water -Outgassing -Comets
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Origin of Earth’s oceans
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• Water vapor released by outgassing • Condensed as rain • Accumulated in ocean basins • About 4 billion years ago • Ice Comets were (maybe) also important to adding water to the Earth system
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Formation of the Atmosphere and the Ocean
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-early solid earth had very hot surface had no atmosphere or oceans -condensing water vapor, thick clouds, heavy rain – as earth cooled, oceans formed 4 bya
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PLANET WATER
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70.8% OF EARTH IS COVERED BY WATER -97% in oceans and seas – 2% lakes and rivers – 1% snow and ice as glaciers – >1% atmospheric water
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What is life?
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a)Homeostasis b)Organization c)Metabolism d)Responds to stimuli e)Adapts f) Reproduces g)Growth
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What is required for life?
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a)Water – essential to all living things b)The right temperature range c)Renewing crust! (CHNOPS) d)Atmosphere (why?) e)Stable energy source
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where did life on earth come from?
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1. Panspermia 2. Frozen Ocean Theory 3. Hydrothermal Vents
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Panspermia
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the proposal that microscopic life forms that can survive the effects of space, such as extremophiles, become trapped in debris that is ejected into space after collisions between planets and small Solar System bodies that harbor life. If met with ideal conditions on a new planet’s surfaces, the organisms become active and the process of evolution begins.
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Frozen Ocean Theory
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– 3 bya, the Sun was thirty percent less luminous than it is today. – there is 300m of ice (protection from UV) – below there is prebiotic chemistry – it is cold so allowed for organic molecules to survive for long periods of time
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Hydrothermal Vents
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-that simple metabolic reactions emerged near ancient seafloor hot springs, enabling the leap from a non-living to a living world. -scientists discovered biological communities unexpectedly living around seafloor hydrothermal vents, far from sunlight and thriving on a chemical soup rich in hydrogen, carbon dioxide, and sulfur, spewing from the geysers.
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Stanley Miller Experiment
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was a Jewish-American chemist who made landmark experiments in the origin of life by demonstrating that a wide range of vital organic compounds can be synthesized by fairly simple chemical processes from inorganic substances. He is aptly regarded as the “father of prebiotic chemistry”
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An ion
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is an atom or molecule where the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge.
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Types of Bonds
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-ionic -covalent -hydrogen
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ionic bond
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electrons are gained or lost – ex sodium chloride ( Na+ Cl-)
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covalent bond
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electrons are shared
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hydrogen bond
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intermolecular bond of H w/ an electronegative atom.
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water molecule
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dipole or polar molecule covalent bond
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Weaker Hydrogen Bonds
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form BETWEEN water molecules
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Stronger Covalent Bonds
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form WITHIN water molecules
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cohesion
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the sticking together of particles of the same substance. ex. surface tension
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adhesion
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the tendency of dissimilar particles or surfaces to cling to one another.
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water composition
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humans- 65% our blood- 83% plants- 95% jellyfish- 99%
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why is water blue?
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Water molecules vibrate, adjacent molecules tug and pull on neighbors, which absorbs a small amount of red light
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Water
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is the Universal Solvent – it can dissolve nearly everything!
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sodium chloride
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-is the salt most responsible for the salinity of the ocean
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Solid crystal structure of sodium chloride
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-each ion is surrounded by six ions of the opposite charge -the larger chloride ions are arranged in a cubic array whereas the smaller sodium ions fill all the cubic gaps (octahedral voids) between them.
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when sodium chloride dissolves into water
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the sodium chloride framework disintegrates as the Na+ and Cl− ions become surrounded by the polar water molecules. -oxygen surround sodium -hydrogen surrounds chloride
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salinity
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-Is the total amount of solid material dissolved in water (not including dissolved organic substances; it is the ratio of the mass of dissolved substances to the mass of the water sample.) -It does not include fine particles in suspension.
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rain dissolves
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rocks
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Dissolved compounds (ions)
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accumulate in ocean basins
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most of the oceans salinity is around
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34-36 PSU
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We express salinity in
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Parts per thousand %
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How do we measure Salinity?
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Principle of Constant Proportion Chlorine (55%) Sodium (30.6%) sulfate (7.7%) magnesium (3.65%) calcium, potassium, and other
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Principle of Constant Proportion
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The major dissolved constituents responsible for the salinity of seawater occur nearly everywhere in the ocean in exact same proportions, regardless of salinity.
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salinity equals
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1.80655 x chlorinity (‰)
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matter exists as
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Liquid (molecules move freely), Solid (molecules locked in place) and Gas (independent molecules)
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to change matter from one form to another
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Add or remove HEAT
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Heat
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– energy produced by the random vibration of atoms or molecules. -measures how many molecules are vibrating and how rapidly
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Temperature
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records how rapidly they are vibrating… It is the object’s response to input or removal of heat!
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water boils at
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212 degrees F 100 degrees C
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water freezes at
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32 degrees F 0 degrees C
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dry ice temp
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-108 degrees F -78 degrees C
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liquid air at
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-312 degrees F -200 degrees C
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absolute zero matter
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-459 degrees F -273 degrees C
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heat can come from
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fire, friction, chemicals and radioactivity
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Calorie
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the amount of heat required to raise temperature of one gram of water by 1°C
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Heat Capacity
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is the amount of heat required to raise the temperature of a substance by 1 degree centigrade.
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High heat capacity
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then the substance can absorb or lose large quantities of heat with only a small change in temperature.
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solid to liquid (both ways)
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-freezing (release heat) -melting (absorb heat)
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liquid to gas (both ways)
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-condensation (release heat) -vaporization (absorb heat)
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solid to gas
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sublimation (absorb heat)
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gas to solid
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deposition (release heat)
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Latent Heat
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Quantity of heat gained or lost per unit of mass as a substance undergoes a change of state.
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evaporation
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Conversion of a liquid to a gas below the boiling point
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as density rises…
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cold water rises, warm water sinks
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as density decreases…
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warm water rises, cold water sinks
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density vs temperature
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density decreases as temperature increases
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on the outside of the pacific, atlantic and indian ocean
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evaporation latitudes and then precipitation latitudes
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ocean day and night temperature
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usually no change in day and night, but some areas the day is a bit cooler
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Francis Bacon (1561-1626) and plate tectonics
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-created the scientific method -indirect role in the plate tectonic theory -potted that the west coast of Africa and the east coast of South America looked as if they would fit together, like pieces of a jigsaw puzzle.
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Ben Franklin (1706-1790) and plate tectonics
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he speculates that the planet’s surface could be floating on a dense liquid and subject to movement as the liquid flowed.
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Antonio Snider-Pellegrini (1802-1885) and plate tectonics
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-The first credible proponent of continental drift -made these two maps showing his version of how the American and African continents may once have fit together, then later separated.
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Edward Seuss (1885)
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-credited for generating many of the concepts that led to the theory of plate tectonics -findings of Glossopteris (an extinct fern-looking tree) in India, South Africa, South America and Australia to propose a past super-continent called Gondwanaland.
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Alfred Wegener (1912)
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-proposed that the continents were once compressed into a single protocontinent which he called Pangaea (meaning “all lands”), and over time they have drifted apart into their current distribution. (about 200 million years ago) -hypothesis lacked a geological mechanism to explain how the continents could drift across the earths surface as he proposed. -came across a paleontological paper suggesting that a land bridge had once connected Africa with Brazil. paleontological observation that the same fossilized plants and animals from the same time period were found in South America and Africa. The same was true for fossils found in Europe and North America, and Madagascar and India. (less likely than the drift theory) -Wegener’s explanation was that as the continents moved, the leading edge of the continent would encounter resistance and thus compress and fold upwards forming mountains near the leading edges of the drifting continents. -another explanation is continental glaciation in the Pensylvanian period. Striae left by the scraping of glaciers over the land surface indicated that Africa and South America had been close together at the time of this ancient ice age. The same scraping patterns can be found along the coasts of South America and South Africa.
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example of mountain theory
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The Appalachian Mountains extend to mountains in Greenland, the United Kingdom and Norway, indicating that these land masses were once joined….
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Continental Drift Hypothesis Lines of Evidence
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Fit of Continents Matching Mountain Sequences Evidence of Glaciers – global ice age? -continents moved Distribution of Organisms
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Mechanisms and Doubt
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-Continents “plow” through the ocean basins. -Calculations showed this to be incorrect -Continents moved because of gravitational attraction of equator and sun/moon. -Gravitational forces are too small.
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Structure of the Earth depends
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on density
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Density Stratification:
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-Earth has distinct layers -Each deeper layer is heavier than the next.
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Density
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expression of heaviness amount of mass contained in a volume
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mantle density
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dense, hot rocks,
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core density
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outer core- liquid (9900F) inner core- solid (12000F) iron, nickel
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continental crust
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-low density rocks made of aluminum, silicon, and oxygen -thick, light -granite, course, and light colored -less dense the ocean -floats higher
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increase in pressure
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=higher melting point
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layers of earth
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-continental/oceanic crust -lithosphere -asthenosphere (upper mantle) -Mesosphere (mantle) -outer core -inner core
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oceanic crust
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-ocean -thin, dense -basalt -texture fine and course -dark color -floats lower in the mantle
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the moho
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-the boundary between the crust and the mantle(even denser rock) – the moho is closest to the oceanic crust
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If weight added or removed from object floating
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equilibrium disturbed!
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Isostatic Adjustment
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-the vertical mvmt.of the crust. -The result of the buoyancy of the earth’s Lithosphere as it floats on the denser, plastic-like asthenosphere below.
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ocean and continetnal crust
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bc there is a thick mass of crustal material Beneath them, buoying them up…
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Isostatic Rebound
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is the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period -Canada depressed from 1640-2300 feet below its present level under cover of ice 1.2-1.9 miles thick
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ring of fire
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-the boundaries of several plates, are dotted with many active volcanoes that form the so-called Ring of Fire. -provides excellent examples of plate-boundary volcanoes, including Mount St. Helens. – is a direct result of plate tectonics and the movement and collisions of lithospheric plates.
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More Evidence of Continental Drift
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Oceanic crust younger than continental crustMid-Atlantic ridge conforms to shoreline -very thin amount of sediment in deep ocean -deep trenches at continental margins -undersea volcanoes had flattened tops
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Harry Hess
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-Considered one of the “founding fathers” of the unifying theory of plate tectonics -During WWII left his depth recorder on all the time…. Noticed Two things: -Extensive mountain ridges in the centers of ocean basins. (mid ocean ridges) -Extremely, deep ocean trenches at the edge of ocean basins. (deep trenches at continental margins) Also, -Undersea volcanoes had flattened tops… -Less sediment at mid ocean ridges… -Oldest fossil found in the ocean – ~ 180 mya. (life on earth much older – ~3.5 bya – found seafloor spreading
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As rocks age and cool…
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they become more dense, and due to isostasy, the ocean crust sinks deeper into upper mantle. Seafloor gets deeper with distance from mid-ocean ridge
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isostasy
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the state of gravitational equilibrium between the earth’s lithosphere and asthenosphere such that the tectonic plates “float” at an elevation which depends on their thickness and density.
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Oldest Sea floor rock
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180 million
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Oldest Continental Rock
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4 billion
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Geopoetry
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(seafloor spreading) 1. New ocean crust formed at ridges 2. Volcanoes that form along the ridge are originally close to the surface of the ocean where they can be eroded flat on top 3. Deep ocean trenches are where the seafloor finally descends back into the mantle 4. Mud and sediments deposited on the ocean floor thin toward the mid-ocean ridges is because the age of the seafloor gets younger, thus less and less time to accumulate sediments
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Mid Oceanic Ridge
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worlds longest mountain chain didnt see this until the 1950s -less sediment
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Marie Tharp
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Mapmaker of the Ocean Floor – revealed the presence of the Mid-Atlantic Ridge and revolutionized scientific understanding of continental drift.
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Tharp scientific understanding of continental drift
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-very thin amount of sediment in deep ocean -deep trenches at continental margins -undersea volcanoes had flattened tops -less sediment at mid-oceanic ridges
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Drummond Matthews Fred Vine
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Measured the first magnetic Anomalies in the Indian Ocean.
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the history of plate movements was captured in
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Residual Magnetic Fields
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Paleomagnetism
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-strips of alternating magnetic polarity at spreading regions. -these patterns support plate tectonic theories -The molten rocks at the spreading center take on the polarity of the planet while they are cooling, then move slowly in both directions from the center. When Earth’s polarity reverses, the polarity of newly formed rock changes, creating symmetrical bands of opposite polarity.
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When scientists conducted a magnetic survey of a spreading center, the Mid-Atlantic Ridge
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they found bands of weaker and stronger magnetic fields frozen in the rocks.
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THE SEAFLOOR ACTS AS
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A GEOLOGICAL ‘TAPE RECORDER’
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Magnetic Anomalies:
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variation in the Earth’s magnetic field, were a historical record of new sea floor
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Magnetic North on the Earth
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-is really the South pole of the earth’s magnet b/c the – “North-seeking Pole” of a magnet (what we call “the North Pole”) is attracted to it (and un-like poles attract). -“The place on earth to which the North Pole of magnets point.”
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Carl Friedrich Gauss
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-First measured the magnetic field in 1835 -data created by satellites with sensitive magnetometers
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Earth’s Magnetic Field
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-Appears to flip at random intervals… 0.1 to 50 my periods -last flip was 780,000 years ago
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magnetic field impact on animals
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-loggerhead sea turtles lay their eggs according to magnetic fields -birds migrate because magnetic fields
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Magnetite
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formed from cooling magma that contains iron oxide
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Other planets do have magnetic fields
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Jupiter, Saturn, Uranus and Neptune – all have fields stronger than the earth’s. mechanism unclear.
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mars and moon have
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magnetic surface areas, suggesting they might have had a field in the past, however they don’t know.
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Why Does Earth’s Magnetic Field Flip?
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So the rare field reversals are most likely caused by larger changes in the flow in the outer core, or in the way in which the field lines are wound into the flow by diffusion. What causes such major changes is not known. Indeed, it may be that such fluctuations are simply extreme examples of the continuum of fluctuations in the dynamo processes–an El Nino in the weather of the outer core.”
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Mid Ocean Ridge causes movement
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-ridge push -slab pull (suction) (stronger movement)
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ridge push
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two plates in mid ocean ridge, magma drives itself upwards and pushes the ridges apart
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slab pull (suction)
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-conveyer belt movement- old dense heavy plates sinks- pulling plates behind
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How Fast Do Plates Move?
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On average – 2-12 cm (1 – 5 inches) same rate as nails
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The lithospheric plates interact with the neighboring plates in several ways.
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-divergent -convergent -transform
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Movement caused by plate tectonics
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1.Divergent Plates: 2.Convergent Plates 3.Transform Plates
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Divergent Plates
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Boundaries between plates moving apart Divergent oceanic crust – for example, the Mid-Atlantic Ridge Divergent continental crust – for example, the Rift Valley of East Africa.
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Convergent Plates
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-Regions where plates are pushing together. Compression produces buckling and shortening.
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Transform Plates
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sliding past eachother Tectonic process – transform faulting Continent-Continent and Ocean crust interaction Sea floor is not created or destroyed… continent example-The San Andreas Fault ocean example- – Btw. MORs
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Divergent Plate Boundaries continent
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Tectonic process – Sea floor spreading; new sea floor is created Continent – Continent – Continental Rifting
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East pacific rise
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Fast spreading – broader, less rugged Total spreading rate: ~16.5 cm per year!
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Earthquakes at divergent boundaries:
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Amount of energy released is related to spreading rate! Faster the spreading – less energy is released in each earthquake….
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Divergent Plate Boundaries oceans
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tectonic process- sea floor spreading: new sea floor when ocean to ocean crust interaction
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two types of divergent plate boundaries
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Divergent oceanic crust – for example, the Mid-Atlantic Ridge Divergent continental crust – for example, the Rift Valley of East Africa.
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three types of convergent plate boundaries
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1. Ocean-Continent 2. Ocean-Ocean 3. Continent-Continent
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Ocean-Continent Convergence
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Tectonic process – Subduction Ocean -Continent crust interaction- Old Sea floor is destroyed example- the andes
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The Andes
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The convergence of the Nazca and South American Plates has deformed and pushed up limestone strata to form towering peaks of the Andes, as seen here in the Pachapaqui mining area in Peru.
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Oceanic Convergence
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Tectonic process – Subduction Ocean – Ocean crust interaction Old Sea floor is destroyed (example -Aleutian Islands
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Continent-Continent Convergence
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Tectonic process – Collision Continent-Continent crust Interaction Sea Floor is not created or destroyed… ex. Himalayan Mountain Range
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Characteristics of good housing
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Available • Big enough (size) • Good condition (roof isn’t leaking, heat works, etc) • Affordable
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Coenobita clypeatus hermit crabs
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are constantly in search of new real estate
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Fit and Damage
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two measures of shell quality
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Poor fit leads to:
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Limited growth potential (Angel 2000) Reduced reproductive fitness (Fotheringham 1976) Greater susceptibility to predation (Angel 2000) Increased dehydration stress (Taylor 1981)
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Shell damage leads to:
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increased mortality risk from predation and desiccation
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How do hermit crabs acquire new real estate?
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One empty shell can trigger a chain – a vacancy chain!
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Vacancy chains
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a process for distributing resources that are discrete, reusable, and limited to use by single individual/ group at a time.
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Already known:
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-Hermit crabs can form vacancy chains for shell acquisition -Shell assessment by 1 crab & shell fights between 2 crabs well-described
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Still unknown
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1. Does the addition of a single new resource benefit multiple individuals? 2. Does social context influence shell acquisition behavior?
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Crowding Index:
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= 6 leg segments + 1 antenna exposed so CI= 7
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Does the addition of a single new resource benefit multiple individuals?
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Reduced crowding for vacancy chain participants: •On average, 3.2 crabs acquired new shells through vacancy chains • 17 of 19 (89%) of vacancy chain participants gained reduction in shell crowding • Mean reduction in shell crowding = 5.5 fewer segments exposed (paired t-test, p<0.0001) yes
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Do hermit crabs gain improved shell fit from lab-manipulated vacancy chains, even when there is a crab in a damaged shell?
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In 4 out of 5 trials, the vacancy chain terminated when the damaged shell was discarded
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What is the relative importance of poor shell condition versus shell crowding in a crab’s motivation to switch into a new shell?
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Avoiding damage is more important than gaining better fit!
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Can we measure improvements in shell fit/shell damage after the introduction of new shells in a natural population?
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No significant decrease in shell damage Perhaps because shells are continually damaged & weakened All crabs were less crowded after new shell addition!!
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In lab-manipulated intact vacancy-chains, hermit crabs gain improved shell fit
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• First demonstration of aggregate benefits with only a single new resource, and first quantification of vacancy chains in terrestrial hermit crabs
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Extreme shell damage can terminate a vacancy chain
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Pagurus longicarpus marine hermit crabs avoid shells with drill holes
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a stronger motivator in competitive interactions
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is shell damage rather than shell fit
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In a natural population, we observed significant improvements
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in shell fit following the addition of only a few new shells
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The addition of a single new resource
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benefits multiple individuals
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Social behavior involved in vacancy chains –
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resource acquisition behavior influenced by social contex
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Different social contexts of vacancy chains:
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-asocial (on your own) -vacancy chains- social
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Asynchronous
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-Delayed switching of shells -Low probability of finding an optimal shell -Permits reversible shell switching -No risk of injury from con-specific agonistic encounters
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Synchronous:
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Simultaneous switching of shells -Increased vulnerability to predators -Time and energy spent forming queue -Higher probability of finding an optimal shell -Increased risk of injury form agonistic encounters -Irreversible shell switching -Greater potential to get stranded in a sub-optimal shell -Higher probability of acquiring an optimal shell -occur within 5 seconds!
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Social contexts impact vacancy chains:
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-The likelihood that a switch is part of a synchronous chain increases with increasing crab density -Asynchronous vacancy chains are more common than synchronous vacancy chains at low crab densities; synchronous chains dominate at high densities
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A synchronous chain requires appropriately sized waiters. At low crab densities
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• fewer potential waiters leads to fewer synchronous chains • substantial gaps in waiter size leads to shorter chains
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social networking: How do waiters recruit other crabs to the scene?
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Chemical? Visual? Tactile?
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Local, marine hermit crabs
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Pagurus longicarpus -800 hermit crab species
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Social contexts are critical for hermit crab shell acquisition behavior
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Social versus asocial behavioral differences for shell investigation and acquisition Model shows that crab density changes the relative frequency of synchronous vs. asynchronous chains

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