Oceanography Textbook Notes PDF

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CHAPTER 1: Introduction to Planet Earth ● 70.8% of Earth’s surface is covered by oceans ● Oceans influence climate and weather ● Pacific Ocean: the world’s largest + deepest ocean ● Arctic Ocean: the smallest and shallowest ocean ● Southern Ocean: surrounds antarctica; its boundary is defined by the antarctic convergence ● Atlantic Ocean: the second largest ocean ● Indian Ocean: exists mostly in the southern hemisphere ● The 4 principle oceans: pacific ocean, atlantic ocean, indian ocean, arctic ocean, southern/antarctic ocean ● The pacific ocean was named in 1520 by the explorer Ferdinand Magellan’s party because they had fine weather (paci = peace) ● The atlantic ocean separates the old world (europe, asia, and africa) from the new world (north + south america) ● What is the difference between ocean and sea?: A sea star lives in the ocean and the ocean is filled with sea water ● Sea: smaller and shallower than the ocean, composed of salt water, somewhat enclosed by land, directly connected to the world ocean ● The average depth of the world’s ocean is 3682 meters (12080 feet) ● How do continents compare to the oceans?: The average height of the continents is only 840 meters (2756 feet), meaning that the average height of the land is not very far above sea. No mountain on earth is taller than the Mariana Trench is deep. ● The seven seas: Red sea, Mediterranean sea, Persian gulf, Black sea, Adriatic sea, Caspian sea, Indian ocean ● The deepest part of the ocean is the Mariana Trench in the Pacific Ocean. It is 11022 meters (36,161 feet) deep and have been visited only twice by humans. ● In the early days, people traveled across oceans to move large/heavy objects, facilitate trade and interaction between cultures. ● Major island groups of the pacific ocean: Micronesia, Melanesia, and Polynesia ● The first mediterranean people known to have developed the art of navigation were the phoenicians ● Greek astronomer-geographer Pytheas sailed northward in 325 B.C. using a simple yet elegant method for determining latitude in the northern hemisphere. ● Europe’s Age of Discovery occurred between 1492-1522 (30 years), where europeans explored the continents of north + south american, and the globe was circumnavigated for the first time ● Europeans first saw the pacific ocean in 1513 ● Oceanography is an interdisciplinary science that overlaps into many scientific disciplines ● Ocean = the marine environment; graphy = description of ● Oceanography is the description of the marine environment ● Oceanology ● People use oceans as a means of transportation and as a source of food

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The four main disciplines of oceanography: geological oceanography, chemical oceanography, physical oceanography, biological oceanography. Geological oceanography: the study of the structure of the seafloor and how the seafloor has changed through time; the creation of seafloor features; and the history of sediments deposited on it Chemical oceanography: the study of the chemical composition and properties of seawater; how to extract certain chemicals from seawater; the effects of pollutants Physical oceanography: the study of waves, tides, and currents; the ocean (atmosphere relationship that influences weather and climate); the transmission of light and sound in the oceans Biological oceanography: the study of various oceanic life-forms and their relationships to one another; the adaptations to the marine environment; developing sustainable methods of harvesting seafood Scientific method: used to formulate scientific theories and separate science from pseudoscience, fact from fiction. The scientific method begins with observations - occurrences we can measure with our senses If an observation is repeatedly confirmed then it can be called a scientific fact Hypotheses: the human mind sorting out the observations in a way that reveals some underlying observation. A hypothesis is a tentative, testable, statement about the general nature of reconsidered and modified observed If observations suggest that a hypothesis is incorrect, it must be dropped. If a hypothesis has been strengthened by additional observations and if it is successful in explaining additional phenomena, then it can be advanced to what is called a theory Theory: a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, logical inferences, and tested hypotheses. Science never reaches an absolute truth because we can never be certain that we have all the observations Science is a process that depends on reexamining ideas as new observations are made Evidence suggests that the sun and the rest of the solar system formed about 5 billion years ago from a huge cloud of gas and space dust called a nebula Nebula: a cloud Nebular Hypothesis: all bodies in the solar system formed from an enormous cloud composed mostly of hydrogen and helium, with only a small percentage of heavip elements. A leading theory states that the moon was born in the aftermath of a collision between a mars-size planet named Theia and proto-earth. Proto-earth: the planet earth at an early stage Thermonuclear fusion: occurs when temperatures reach tens of millions of degrees and hydrogen atoms combine to form helium atoms, releasing enormous amounts of energy. Not only does the sun emit light, it also emits ionized particles (electrically charged) that make up the solar wind.

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Density: mass per unit volume The density of the earth’s atmosphere dramatically affects their locations within earth The density of air masses affects their positions in the atmosphere and other properties The density of water determines how deep in the ocean they are found and how they move Density stratification: when element segregate according to their densities; occurs because of gravitational separation. Based on chemical composition, earth consists of three layers: the crust, the mantle, and the core The crust is composed of relatively low-density rock, consisting of various silicate minerals Two types of crust: oceanic + continental The mantle occupies the largest volume of the three layers and extends to a depth of about 2885 km (1800 miles) The core is composed of even higher-density metal (mostly iron and nickel) Based on physical properties, earth is composed of five layers: the inner core, the outer core, the mesosphere, the asthenosphere, and the lithosphere Lithosphere: earth’s cool, rigid, outermost layer (brittle, will fracture when force is applied) The plates involved in plate tectonic motion are the plates of the lithosphere The asthenosphere is plastic, it will flow when a gradual force is applied to it (relatively hot) Areas of hotter rock cause seismic waves to slow down Areas of cooler rock cause seismic waves to speed up Mesosphere: rigid because of the increased pressure at its depth The core consists of the outer core, and the inner core The increased pressure at the center of the earth keeps the inner core from flowing Continental crust: (granite) low density + thick Oceanic crust: (basalt) high density + thin Viscosity: a measure of a substance’s resistance to flow Isostatic adjustment: the vertical movement of crust Both continental and oceanic crust float on the denser mantle beneath. Oceanic crust is denser than continental crust The rate at which isostatic rebound occurs gives scientists important information about the properties of the upper mantle Isostatic adjustment provides additional evidence for the movement of tectonic plates The formation of earth’s atmosphere is related to the formation of the oceans, both are a direct result of density stratification Originally, earth had no oceans, the oceans and atmosphere came from inside earth as a result of outgassing and were present by at least 4 billion years ago Oxygen comprises almost 21% of earth’s present atmosphere Bodies need oxygen to oxidize (burn) food to release energy to our cells; oxygen in the upper atmosphere in the form of ozone protects the surface of the earth from most of the sun’s harmful ultraviolet radiation

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The theory of evolution states that groups of organisms adapt and change with the passage of time, causing descendants to differ morphologically and physiologically from their ancestors Evolution is the process by which various species have been able to inhabit increasingly numerous environments on earth Heterotrophs: require an external food supply Autotrophs: can manufacture their own food supply, evolved later Anaerobic: bacteria that live without atmospheric oxygen Chemosynthesis: the process of deriving energy from inorganic compounds at deepwater hydrothermal vents Chlorophyll: captures the sun’s energy through cellular photosynthesis Photosynthesis: plant/algae cells capture energy from sunlight and store it as sugars, releasing oxygen gas as a by-product. Cellular respirations: where animals who consume the sugars produced by photosynthesis combine them with oxygen, releasing the stored energy of the sugars to carry on cellular tasks important for various life processes The great oxidation event fundamentally changed the earth’s ability to support life Oxygen in the presence of light is highly reactive with organic matter. The older a rock is, the more radioactive material it contains radiometric age dating: a powerful tool for determining the age of rocks The geologic time scale lists the names of the geologic time periods as well as important advances in the development of life forms on earth

Chapter 2: Plate Tectonics and the Ocean Floor ● Revolutionary new theory called plate tectonics explains surface features and phenomena on earth (the new global geology) ● Plate Tectonics: the outermost portion of earth is composed of a patchwork of thin, rigid plates that move horizontally with respect to one another, like icebergs floating on water. ● Plate = plates of the lithosphere; tekton = to build ● As a result of plate tectonics, continents are mobile + move about on earth’s surface, controlled by forces deep within earth ● The tallest mountain range on earth is the Himalaya mountains that extend through india, nepal, and bhutan ● Plate tectonics was not accepted by many scientists when it was first introduced ● Alfred Wegener: a german meteorologist and geophysicist was the first to advance the idea of mobile continents in 1912 ● Continental drift: Wegener’s theory/idea that continents were slowly drifting across the globe ● 1620: Sir Francis Bacon wrote about how the continents appeared to fit together ● 1912: people started paying attention to Bacon’s theory when Wegener used shapes of matching shorelines on different continents as a supporting piece of evidence for continental drift ● Wegener suggested that during the geological past, the continents collided to form a large landmass, which he named Pangaea

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Pangaea: (pan= all ;gaea= earth) A huge ocean called Panthalassa surrounded Pangaea, Panthalassa included several smaller seas including the Tethys Sea Wegener’s evidence indicated that as Pangaea began to split apart, the various continental masses toward their present geographic positions Wegener’s attempt at matching shorelines revealed considerable areas of crustal overlap and large gaps. Some differences could be explained by material deposited by rivers or eroded from coastlines The shallow parts of the ocean floor close to shore are underlain by materials similar to those beneath continents In the early 1960s, Sir Edward Bullard and two associates used a computer program to fit the continents together Many rock sequences from one continent were identical to rock sequences on an adjacent continent - although the two were separated by an ocean Mountain ranges that terminated abruptly at the edge of a continent continued on another continent across an ocean basin, with identical rock sequences, ages, and structural styles Wegener suggested that mountains such as those seen on opposite sides of the atlantic formed during the collision when Pangaea was formed The only places in the world where thick continental ice sheets occur are in the polar regions of greenland and antarctica Evidence of ancient glaciation is found in the lower-latitude regions of south america, africa, india, and australia This indicates one of two possibilities: (1) there was a worldwide ice age at that time, and even tropical areas were covered by thick ice (2) some continents that are now in tropical areas were once located much closer to one of the poles. Unlikely that the entire world was covered by ice 300 million years ago because coal deposits from the same geological age now present in north america + europe originated as vast semitropical swamps Certain continents have moved from more polar regions during the past 300 million years = another type of glacial evidence When glaciers flow, they move and abrade the underlying rocks, leaving grooves that indicate the direction of flow Examples of plant + animal fossils indicate very different climates than today Earth’s past environment can be interpreted from these rocks because plants and animals need specific environmental conditions in which to live When fossil corals are found in areas that are cold today, two explanations are plausible: 1) worldwide climate has changed dramatically; 2) the rocks have moved from their original location The fossil remains of mesosaurus are located only in eastern south america and western africa Mesosaurus: an extinct, presumably aquatic reptile that lived about 250 million years ago Mesosaurus: meso = middle saurus = lizard

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Wegener: continents were closer together in the continental past, after mesosaurus became extinct, the continents moved to their present-day positions, and a large ocean now separates the once-connected land masses Wegener first published his ideas in The origins of continents and oceans in 1915 - the book did not attract much attention until it was translated into English, french, spanish and russian in 1924 Wegener: the continents plowed through the ocean basins to reach their present-day positions and that the leading edges of the continents deformed into mountain ridges because of the drag imposed by ocean rocks The driving mechanism Wegener proposed a combination of the gravitational attraction of earth’s equatorial bulge and tidal forces from the sun and moon Analysis of gravitational and tidal forces indicated that they were too small to move the great continental landmasses Many geologists accepted continental drift because it was consistent with the rock record In order for any scientific viewpoint to gain wide acceptance it must explain all available observations and have supporting evidence from a wide variety of scientific fields Studies of the sea floor using sonar were initiated during world war 2 and continued afterwards to provide critical evidence in support of drifting continents Technology unavailable in wegener’s time enabled scientists to analyze the way rocks retained the signature of the earth’s magnetic field Earth’s magnetic field plays a crucial role in guiding navigators + also protects earth’s life-forms from solar storms The invisible lines of magnetic force that originate within earth and travel out into space resemble the magnetic field produced by a large bar magnet Igneous Rocks: solidify from molten magma either underground or after volcanic eruptions at the surface that produce lava Magma = a mass Lava = to wash Nearly all igneous rocks contain magnetite, a naturally magnetic iron mineral Particles of magnetite in magma align themselves with earth’s magnetic field because magma and lava are fluid Once molten material is cooled to a certain temperature, internal magnetite particles are frozen into position, thereby recording the angle of earth’s magnetic field at that place + time. Grains of magnetite serve as tiny compass needles that record the strength and orientation of earth’s magnetic field. As long as the sediment is surrounded by water, the magnetite particles can align themselves with earth’s magnetic field After sediment is buried and solidifies into sedimentary rock, the particles are no longer able to realign themselves if they are subsequently moved Most reliable rocks are igneous rocks that have high concentrations of magnetite such as basalt Basalt is the rock type that comprises oceanic crust

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Paleomagnetism: the study of earth’s ancient magnetic field Scientists who study paleomagnetism analyze magnetite particles in rocks to determine not only their north-south direction but also their angle relative to earth’s surface Magnetic dip: the degree to which magnetite particle points into earth, also called magnetic inclination Magnetic dip is directly related to latitude At earth’s magnetic north pole, the dip needle points straight into the ground Magnetic dip increases with increasing latitude from 0 degrees at the magnetic equator to 90 degrees at the magnetic poles Paleomagnetism is a powerful tool at interpreting where rocks first formed Magnetic compasses on earth follow lines of magnetic force and point toward magnetic north The north and south magnetic poles reverse or switch so that magnetic north becomes magnetic south and vice versa Geophysicists who study earth’s magnetic field do not yet fully understand the process of magnetic polarity reversals, but they are in agreement that earth’s rotation causes the electrically conducting liquid iron outer core to generate a self-sustaining magnetic field Computer simulations of earth’s core reveal frequent flipping of earth’s magnetic field Paleomagnetic studies reveal that 184 major reversals have occurred in the past 83 million years Changes in earth’s magnetic polarity are identified in rock sequences by a gradual decrease in the intensity of the magnetic field of one polarity, followed by a gradual increase in the intensity of the magnetic field of opposite polarity Geologic evidence indicates that earth’s magnetic field has also been weakening during the past 2000 years Geophysicists think that the diminishing strength of earth’s magnetic field may be an indication that earth’s current “normal” polarity may reverse itself Magnetometer: instrument that measures the earth’s magnetic field and how it was affected by the magnetic properties of rocks on the ocean floor An anomaly is a departure from normal conditions Magnetic anomalies: a pattern of alternating stripes of above average and below average magnetism Harry Hess (1906-1969): geologist, published history of ocean basins in 1962 which contained the idea of seafloor spreading and the associated circular movement of rock material in the mantle- convection cells, as the driving mechanism Hess suggested that new ocean crust was created at ridges, split apart, moved away from the ridges, and later disappeared back into the deep earth at trenches Mid-ocean ridge: a continuous underwater mountain range that winds through every ocean basin in the world + resembles the seam on a baseball. It is entirely volcanic in origin, wraps one and a half times around the globe, and rises more than 2.5 km above the surrounding deep-ocean floor. New ocean floor forms at the crest or axis of the mid-ocean ridge By the process of seafloor spreading, new ocean floor is split in two and carried away from the axis, replaced by the upwelling of volcanic material that fills the void with new

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strips of sea floor Spreading center: seafloor spreading occurs along the axis of the mid-ocean ridge Ocean floor is being destroyed at deep ocean trenches Trenches are the deepest parts of the ocean floor ...