Transcript Oceanic
Unit 10 Oceans Mr. Ross Brown Brooklyn School for Law and Technology How do we learn about Earth’s oceans? • 23 March 2016 • Do now: What separates the different oceans of the Earth? In this unit we will learn about: • The Water Planet – Divisions of Global Oceans – Ocean Exploration • Features of the Ocean Floor – Continental Margins – Deep Ocean Basins • Ocean Floor Sediments – Sources of Deep Ocean Basin Sediments – Physical Classification of Sediments How do we learn about Earth’s oceans • Almost 75% of Earth’s surface is ocean – Earth is unique in our liquid water • 3 Major Oceans – Atlantic, Pacific, Indian – Seas: smaller areas of water surrounded by land – Pacific Ocean: more than 50% of oceans • Average depth of 3.9 km How do we learn about Earth’s oceans • How do we explore oceans? – Oceanography: the study of physical characteristics, chemical composition, and lifeforms in the ocean. – Ocean floor: continental and oceanic crust under the ocean waters. How do we learn about Earth’s oceans • Submersibles: underwater research vehicles • Bathysphere: spherical diving vessel • Bathyscaphe: deep-research, self-propelled Homework #21 • 23 March 2016 • How does Sonar enable an underwater vessel to steer its way through the ocean depths? What are the features of the ocean floor? • 24 March 2016 • Do now: if you could travel to the floor of the ocean, what would you see? What are the features of the ocean floor? • Ocean floor composed of two parts: – Continental margin: shallow, continental crust and sediments – Deep ocean basin: oceanic crust and a thin layer of sediment What are the features of the ocean floor? • Continental shelf – Part of continent covered by water – Width varies What are the features of the ocean floor? • Continental slope – Past the shelf, steeper slope. What are the features of the ocean floor? • Submarine canyon and continental rise What are the features of the ocean floor? What are the features of the ocean floor? • Deep ocean basins – Trenches: found near subduction zones, deepest places on earth What are the features of the ocean floor? • Abyssal plains: vast flat areas in deep ocean basins What are the features of the ocean floor? • Mid-ocean ridges What are the features of the ocean floor? • Sea mounts – Submerged volcanic mountains at least 1000m high. What are different ocean environments? • 29 March 2016 • Do now: Into how many different environments can we divide the oceans? What are different ocean environments? • Benthic zones (bottom) – Intertidal or littoral zones (shallowest) • Between low- and high-tide • Unstable, yet life flourishes here What are different ocean environments? • Sublittoral zone – Shallow yet continuously submerged – Largest number of benthic organisms What are different ocean environments? • Bathyal zone – Begins at continental slope and extends to 4,000m deep – Little sunlight, few plants, fewer organisms • Abyssal zone – No light, to 6,000m deep What are different ocean environments? • Hadal zone – In ocean trenches, deeper than 6,000m. What are different ocean environments? • Pelagic zones – Water zones. Animals living above the bottom. – Neritic zone • Above continental shelves. Good sunlight. Lots of plankton. What are different ocean environments? • Oceanic zone – Deep and open oceans beyond continental shelf – Divided into 4 zones based on amount of sunlight • Epipelagic: uppermost. Abundant life. Tuna, dolphin, sargassum weed. • Mesopelagic, bathypelagic, abyssopelagic occur at increasing depth. With depth, less sunlight, less life. What are different ocean environments? How does water move about the oceans? • 30 March 2016 • Do now: What causes waves? How does water move about the oceans? • Currents: identifiable patterns of ocean water movement – Surface currents: driven by winds – Deep currents: move slowly, caused by differences in water density How does water move about the oceans? • Surface currents are controlled by: – Wind belts How does water move about the oceans? • Surface currents are controlled by: – The Earth’s rotational effects • Coriolis Effect • Wind belts and Coriolis Effect combine to produce Gyres, huge moving circles of water in oceans How does water move about the oceans? • Gyres How does water move about the oceans? How does water move about the oceans? • Our Gulf Stream – Water from Gulf of Mexico and Caribbean Sea pushes up along Eastern Seaboard How does water move about the oceans? How does water move about the oceans? • Deep currents – Cold, dense polar water sinks and flows beneath warm ocean water towards the equator. – Density differences due to temperature & salinity How does water move about the oceans? How does water move about the oceans? • North Atlantic Deep Water Homework #22 • 30 March 2016 • What force is responsible for most surface currents? • What two factors affect the density of ocean water and cause deep currents? • Answer in complete sentences or lose credit. How does water move about the oceans? • 31 March 2016 • Do now: How can we measure the speed of a wave? How does water move about the oceans? • Waves: the periodic up and down movement of water – Crest: highest point of a wave – Trough: Lowest point between two crests – Wave height: vertical distance between crest and trough – Wave period: time it takes for one wavelength to pass a given point How does water move about the oceans? Wavelength Wave speed = -----------------Wave period How does water move about the oceans? • • • • With no wind, water would appear like glass Wind results in friction between air and water More wind pushes against ripples Waves grow How does water move about the oceans? • Water movement in a wave – The energy passes through the water, but the water doesn’t move forward How does water move about the oceans? • Wave size – Determined by wind speed, length of time wind blows, and fetch – Fetch: distance the wind blows across open water How does water move about the oceans? • When depth of water is about ½ wavelength, the top of the wave gets ahead of the bottom due to friction. The wave may topple over as a breaker How does water move about the oceans? • Undertow: water carried onto the beach by a breaker is pulled back into deep water • Rip current/ riptide: water returning from the beach gets caught in channels, thus becoming stronger. DANGEROUS! How does water move about the oceans? How does water move about the oceans? • Tsunamis – NOT caused by wind – Caused by underwater seismic activity How does water move about the oceans? • 1 April 2016 • Do now: Yes, tides are caused by the Moon’s gravity. How? How does water move about the oceans? • Tides – Daily changes in the level of the ocean surface – The gravitational pull of the Moon is strongest on the Earth’s nearest side How does water move about the oceans? • Also influenced by the Sun How does water move about the oceans? • Spring tide: Earth, Sun, Moon aligned, tides amplified. • Neap tides: 1st and 3rd quarter Moon, so Moon and Sun are at right angles relative to the Earth. Smaller tides. How does water move about the oceans? • Tidal currents: the movement of water caused by tides. • Flood tide moves toward the coast, ebb tide is water moving away. Between flood and ebb is slackwater. How does water move about the oceans? • Bay of Fundy, Nova Scotia Canada • World’s greatest tidal range (high to low) How does water move about the oceans? How does water move about the oceans? How does water move about the oceans? • Tidal currents at coastline can be impressive • Influenced by shape of coastline • Tidal bore: surge of water rushing upstream