Transcript oceans
Chapter 3 Geology of the Ocean Karleskint Turner Small Key Concepts • The world ocean has four main basins: the Atlantic, Pacific, Indian, and Arctic. • Life first evolved in the ocean. • The earth’s crust is composed of moving plates, and the seafloor is always changing Key Concepts • The ocean floor has topographical features similar to those found on continents. • The seafloor is composed of sediments derived from living as well as nonliving sources. • Latitude and longitude determinations are particularly necessary for precisely locating positions in the open sea, where there are no features at the surface. World Ocean • Ocean and the origin of life – Stanley Miller’s apparatus – No oxygen (no photosynthesis!) in atmosphere ~ 4bya World Ocean • First cells were most likely anaerobic bacteria World Ocean • The ocean today: all “oceans” are connected! World Ocean • The ocean today – 4 major ocean basins: • Pacific (largest), Atlantic, Indian, Arctic – Sea: smaller than ocean, essentially landlocked – Gulf: large area of sea or ocean, partially enclosed by land – Strait or Channel: narrow body of water connecting 2 large areas of ocean – Bay, bight, fjord, inlet: open to 1 side only – Sound: open to 1 or both sides Continental Drift • Continents are always in (slow) motion • New seafloor is produced at ocean ridges • Old seafloor is removed at ocean trenches Continental Drift • Rift (Deep Sea Vent) Communities – specialized environments found at divergence zones of the ocean floor – primary producers are chemosynthetic bacteria Rift valley Ocean Bottom • Bathygraphic features – Geological features similar to land: mountain ranges; canyons, valleys; great expanses Ocean Bottom • Continental margins – continental shelf, continental slope, and shelf break Ocean Bottom • Ocean basin – – – – abyssal plains and hills seamounts ridges and rises trenches and island arcs Ocean Bottom • Life on the ocean floor – continental shelves are highly productive – life on the abyssal plains is not abundant, no sunlight, no photosynthesis Composition of the Seafloor • Sediment—loose particles of inorganic and organic material S&T! Composition of the Seafloor Sediments – formed from seawater through a variety of chemical processes – formed from remains of living organisms: corals, shells of mollusks or planktonic organisms – produced from continental rocks by the actions of wind, water, freezing, thawing – from outer space Biogenic sediments Finding Your Way around the Sea • Charts Finding Your Way around the Sea • Reference lines: latitude & longitude Finding Your Way around the Sea • Navigating the ocean – Sextant to determine latitude with reference to Polaris – Chronometer to determine longitude by measuring time relative to Earth’s rotation NOAA Bjoertvedt Navigating the ocean by Global Positioning System (GPS) Finding Your Way around the Sea • utilizes a system of satellites to determine position • GPS measures the time needed to receive a signal from at least 3 satellites, and calculates position NASA