Q: Almost everyone knows that most of the Earth’s surface is covered in water. Where did all that water come from? Link

Bathymetry The study of the depth/topography of the floor of a body of water

SONAR Short for Sound Navigation and Ranging Originally used for submarine detection during WWII Used since to map ocean floor topography

BATHYMETRY OF THE OCEAN FLOOR Structures on the ocean floor are mapped by SONAR - sound navigation and ranging (echo sounding) (speed of sound in H20) depth = time x 1500 meters/sec 2 (round trip) sea floor

Do Now: Sound travels at 1500 meters per second in water Do Now: Sound travels at 1500 meters per second in water. How deep is the ocean bottom if the sonar signal is received 6 seconds after it was sent? 6 seconds there and back 1500 meters = 4500 meters deep 1 second 2 trips

Do Now: Sound travels at 1500 meters per second in water Do Now: Sound travels at 1500 meters per second in water. The Mariana trench is 10,809 meters deep. How long will it take for sound to travel from the surface of the water above and back? Show your work. 10,809 m one way 2 (RT) 1 second = 14.4 sec 1500 meters

THE WORLD OCEAN Covers 71 % of the planet (59.4 % is seafloor) Divided into major basins – Atlantic (N & S), Pacific, Arctic, Indian, Southern Pacific – largest & deepest

Continental Margin: the submerged outer edge of a continent marks the transition between continent and ocean, composed of shelf, slope & rise a. continental shelf - underwater extension of the continent, most biologically productive area because of light availability b. continental slope – sloping transition between the continent (granite) and the deep-ocean floor (basalt) - sediments tumbling down the slope can form turbidity currents which cut submarine canyons (deep, V-shaped valley running perpendicular to the shoreline) c. continental rise – wedge of sediments covering the joint between ocean crust and continental crust Continental Margin NOAA

JQ: Do any organisms use sonar? Explain Also called Bio Sonar, many dolphins, toothed-whales, cave swiftlets, shrews, tenrecs Link Link

Do Now: At its deepest point, Greenwood Lake is approximately 60 feet deep. About how long would it take to receive a signal back from a sonar ping from a boat above that spot in the lake. Remember, sound travels at 1500 meters per second in water.

Ocean Basin Features: a. abyssal plain - flat, featureless region similar to a desert; common in Atlantic and Indian Oceans, rare in the Pacific b. abyssal hill - occur where sediment is not thick enough to cover the underlying rock completely. Usually extinct volcanoes or small formations of rock once extruded in molten form. c. seamount - peaks of volcanic mountains (sea mountains, completely underwater) d. guyot - submerged, inactive volcano flattened by erosion e. island - seamounts extending out of the water. They differ from continents because they have no margins. f. trenches – arc-shaped depression in the deep-ocean floor with very steep sides and flat sediment-filled bottoms, associated with subduction zones where ocean crust is being recycled into the mantle

ABYSSAL PLAIN

TRENCH

Iceland is a large section of the MOR extending above the water. Mt. Everest, at 29,000 ft., could fit into the Mariana trench and still be 7,000 ft. below sea level. g. Mid-Ocean Ridge (MOR) - 40,000 mile long mountain range where new oceanic floor is being formed. Divergent plate boundaries are found in all parts of the ocean - not just in the middle of the Atlantic. NOAA Iceland is a large section of the MOR extending above the water.

h. rift “valley” – down-dropped section of a MOR occurring at divergent plate boundaries, outpouring of magma creates new ocean floor NASA Oceanic bathymetry is very similar to continental topography except that continent features are smaller due to erosion

SONAR Lab

Question: Hypothesize at least two ways in which sonar might affect marine organisms

Read Article 1 and answer questions 1-3. Read Article 2 and answer remaining questions. Link to article

In a group of no more than 4: Review your answers to the post-reading questions Discuss the following: What’s fishy (pun intended) about article 1? What bathymetric features do the Mediterranean and Caribbean seas share that California and Japan lack? How might the Bathymetric features of these locations influence mass strandings? Explain.