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Exploring Earth's Oceans: Composition, Movements, and the Role of Oceanography

This chapter delves into Earth's oceans, which cover over two-thirds of the planet and contain 97% of its water. It highlights the work of oceanographers studying water chemistry, marine organisms, and sediment data collection. Techniques such as sonar, floats, and satellites are used to map oceanic features and monitor temperatures and salinity. The origins of Earth's water, the distribution of oceans, and the chemical composition of seawater are explored. Additionally, the chapter discusses ocean stratification, movements, and the causes of tides and currents.

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Exploring Earth's Oceans: Composition, Movements, and the Role of Oceanography

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  1. Chapter 15 Earth’s Oceans

  2. The Global Ocean • One vast body of water covering more than two thirds of Earth’s surface • Oceans contain 97% of the water on Earth • Oceanographers study the oceans: • Water chemistry • Wave action • Marine organisms • Sediments

  3. Data Collection • Surface • Sonar—find the depth of the ocean, map undersea mountain ranges • Floats and Satellites (TOPEX/Poseidon)—map temperature, salinity, wave motion • Deep water—unmanned and manned submersibles (Alvin) • Computers—model information about tides, tsunamis, pollution, climate change

  4. Research Ships Sentry and Alvin HMS Challenger

  5. Origin of the Oceans • Oceans have existed almost since the beginning of Earth’s geologic history. • Evidence indicates that the source of the water on Earth was • volcanic eruptions (water vapor) • impacts with comets and meteorites

  6. Distribution of Earth’s Water • The southern hemisphere has much more water than the northern hemisphere.

  7. Sea level changes (due to melting glaciers and thermal expansion)

  8. Major Oceans • Pacific • Atlantic • Indian • Arctic • Southern

  9. Chemical Composition of Seawater • Water • NaCl • MgCl2 • KCl • CaCl2 • Average salt concentration is 3.5% (varies from 3.2% to 3.7%) • Salt added and removed is in equilibrium

  10. Ocean Stratification (Layering) • Ocean water forms layers based on density, caused by temperature and salinity differences

  11. Water Masses • AABW: Antarctic Bottom Water—coldest and most dense • NADW: North Atlantic Deep Water—less dense than AABW

  12. Ocean Movements: Waves

  13. Waves • Shallow water causes waves to slow down

  14. Ocean Movements: Tides • Tides are caused by gravitational effect of both the Moon and the Sun • Spring Tides: higher tidal range • Neap tides: lower tidal ranges

  15. Ocean Movements: Currents • Gyres (horizontal surface currents) transfer heat from equator to poles

  16. Ocean Movements: Currents • Density currents (ocean conveyor belt) move vertically as well as horizontally

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