3 AN OCEAN WORLD The ocean covers 71% of Earth’s surface The ocean contains 97% of the water on EarthThe ocean is Earth’s most important featureThe named oceans and seas (Pacific and Atlantic, Mediterranean and Baltic) are named for our convenienceThey are only temporary features of a single world oceanAverage ocean depth is about 4½ times greater than the average height of the continents above sea level
5 Earth is a Water Planet oceans occupy 71% of the earth's surface not distributed equally with respect to the equatorocean covers 61% of the northern hemisphere and 80% of the southern hemispherepresence of oceans is function of geological activity and planet's location in relation to suntoo far away -- water will be in a frozen statetoo close -- water will evaporateEarth is in a perfect location to allow water to be in liquid state
7 Oceans Today's oceans are traditionally divided into 4 large basins North and South PacificNorth and South AtlanticIndianArcticOceans are really interconnectedConnected to these 4 large basins are smaller, marginal seas, such as the Mediterranean, Gulf of Mexico, South China Sea, Red Sea, Caribbean, Baltic Sea, Bering Sea, etc.Each basin or marginal sea varies in its ability to support life due to both climatic differences and shapes and positions of present-day continentsOcean basins consist of the deep seafloor (13,000-20,000 ft; 4-6 km) and cover most of the earth's surface (30%); continents only cover 29%
14 3-D Computer Generated Image of the East Pacific Rise
15 The Big Bang Event that occurred approximately 13.7 BILLION years ago All the mass and energy concentrated at a pointThe universe began expanding and continues to expandAfter 1 million years matter began to cool enough to form atoms- Hydrogen- the building block of stars
17 Galaxies and StarsGalaxy- huge rotating aggregation of stars, dust, gas held together by gravityEarth, the sun and our solar system is part of the Milky WayStars are massive spheres of incandescent gases (hydrogen and helium)
18 The Solar SystemOur solar system is located away from the galaxy’s centerOur sun and the planets originated from a solar nebula that had been enriched with heavy elements from nearby super novaeSolar system is approximately 5 Billion years oldComposition is 75% hydrogen, 23% helium and 2% other materials
26 The EarthCore is composed of mixtures or alloys of iron (pressure is more than a million times that at the surface and temperature is estimated to be at 4000°C); has a solid inner core and a liquid outer core (earth's magnetic field may be produced by the motion of the liquid material in the iron-rich outer core)Layer outside the earth's core is the mantle; it is solid but very hot, near the melting point of rocks, so it flows almost like a liquid, though much slower; it is 70% of the earth's volume
27 The EarthOutermost layer is the crust; it is extremely thin (is thinner under the oceans than under the continents)Oceanic crust is made of basalt (low in silica and high in iron and magnesium) and has a higher density compared to continental crust, which is made of granite (high content of aluminum and magnesium silicate with quartz and feldspar) and has a lower densityThus, continents lie above sea level and oceanic crust lies below sea level because of density differences
28 Formation of the Oceans: Prevailing Theory The major trapped volatile was water (H2O). Others included nitrogen (N2), the most abundant gas in the atmosphere, carbon dioxide (CO2), and hydrochloric acid (HCl), which was the source of the chloride in sea salt (mostly NaCl).The volatiles were probably released early in the Earth's history, when it melted and segregated into the core, mantle, and crust. This segregation occurred because of differences in density, the crust being the "lightest" material.Volcanoes have released additional volatiles throughout the Earth's history, but probably more during the early years when the Earth was hotter.Probably, the oceans formed as soon as the Earth cooled enough for water to become liquid, about 4 billion years ago. The oldest rocks on the earth's surface today are 3.8 billion years old.
29 OutgassingOceans are byproducts of heating and differentiation: as earth warmed and partially melted, water locked in the minerals as hydrogen and oxygen was released and carried to the surface by volcanic venting activity
31 Origin of Atmosphere Atmosphere evolved in 4 steps: primordial gases, later lost from sun's radiationexhalations from the molten surface (volcanic venting); bombardment from icy cometssteady additions of carbon dioxide, water vapor, carbon monoxide, nitrogen, hydrogen, hydrogen chloride, ammonia, and methane from volcanic activityaddition of oxygen by plant/bacterial life
32 The Hydrologic Cycle Water occurs as a solid, liquid and gas Amount of water is fixedThe places where water resides are called ReservoirsWater constantly moves from one reservoir to another
36 The Origin of Sea SaltsThe sea became salty because of chemicals leached from the rocks of the crust, plus some volatile chemicals (hydrochloric acid and hydrogen sulfide) released from the Earth's interior and by volcanoes.Probably, the ocean was salty as soon as it formed. More salts have accumulated gradually, as more of the rocks of the crust were broken down by water (weathered).The composition of the sea salt has been about the same for about 1 billion years. That is because a balance exists between input of salts (mainly by rivers) and output (mainly by sediments).The early ocean, 3.8 billion years ago, was probably similar in composition to today, except for changes caused by living things. The most important of these is the production of oxygen by plants.