1. Mapping the Ocean Floor

2. Essential Questions  What are some of the features found on the ocean floor?  What technology is used to map the ocean floor?

3. What are some of the features found on the ocean floor?

4. Continental Shelf  A flat, wide margin is found around every continent  The average width of a continental shelf is 70 kilometers  Slopes at an angle of 0.1°, or 1.7 meters per kilometer

5. Continental Slope  The continental slope is about 16 kilometers wide, on average, and descends to a depth of about 2.4 kilometers  The slope of the ocean floor becomes much steeper, typically a 4° slope, or 70 meters per kilometer.  is grooved by submarine canyons and gullies.

6. Continental Rise  The slope moderates to a mere degree or two from horizontal which is called the continental rise  Joins abyssal plain to continental slope

7. Submarine Canyon  is a steep-sided valley on the sea floor of the continental slope  cutting the continental slopes have been found at depths greater than 2 km below sea level.

8. Oceanic Trench  Is where an oceanic crust plate begins to descend beneath another oceanic crust plate  Oceanic trenches typically extend 3 to 4 km below the level of the surrounding oceanic floor.  Trenches are generally parallel to a volcanic island arc, and about 200 km from a volcanic arc.  The greatest ocean depth to be sounded is in the Challenger Deep of the Mariana Trench, at a depth of 10,911 m below sea level.

9. Abyssal Plain  The abyssal plain, which is the deepest, most level part of the ocean, is found where the continental rise ends, at a depth of about 4 kilometers.  The abyssal plain is dotted with thousands of small, extinct volcanoes called abyssal hills.

10. Mid-Ocean Ridge  a long, undersea mountain chain that usually extends down the middle of the ocean  The Mid-Atlantic Ridge, for example, snakes down the middle of the Atlantic most of the way from the North Pole to Antarctica.

11. Rift Valley  Along the center of the mid-ocean ridge is the rift valley, a deep V-shaped notch.  From this valley, new oceanic crust is constantly being extruded from Earth's mantle by processes not yet fully understood.  In the case of the Mid-Atlantic rift valley, one sheet flows east and the other west, each moving at about half an inch per year.  This causes sea floor spreading.

12. Guyot  is an isolated underwater volcanic mountain, with a flat top over 200 meters (660 feet) below the surface of the sea.  the diameters of these flat summits can exceed 10 km.

13. Seamount  is a mountain rising from the ocean seafloor that does not reach to the water's surface, and thus is not an island.  these are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of 1,000–4,000 metres depth

14. Hydrothermal vent  is a fissure in a planet's surface from which geothermally heated water issues  are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots

15. Interesting facts  Mauna Kea, Hawaii, rises 33,474 feet from its base on the ocean floor; only 13,680 feet are above sea level  The ocean ridges form a great mountain range, almost 64,000 km long, that weaves its way through all the major oceans. It is the largest single feature on Earth  Deepest point - 36,198 feet in the Mariana Trench in the western Pacific.

16. What technology is used to map the ocean floor?

17. Historically  For hundreds of years, the only way to measure ocean depth was the sounding line, a weighted rope or wire that was lowered overboard until it touched the ocean floor.  Not only was this method time-consuming, it was inaccurate; ship drift or water currents could drag the line off at an angle, which would exaggerate the depth reading.  It was also difficult to tell when the sounding line had actually touched bottom

18. Present Day  SONAR acronym for SOund Navigation And Ranging  is a technique that uses sound propagation SONAR waves are sent from a ship and the time for the waves to return is measured the farther the distance the longer the time, the shorter the distance the smaller the time