1. What were some of the important findings from the HMS Challenger

2. Major findings included: First plot of currents and temperatures in oceans Map of ocean sediments Outline of main contours of ocean basins Discovery of mid-atlantic ridge (baffled them) Mariana Trench measured at 26,000 feet. Deepest point in ocean. 4,717 new ocean life forms discovered. Discovery of life at depths greater than 18,000 feet.

4. Three major zones Continental margins The ocean basin floor The mid ocean ridge The illustration at right shows the typical topography of an ocean; the continental margin, ocean basin, mid- ocean ridge and again to the next continental margin. Each of these areas has it’s own distinct features

5. Continental Margins: zone of transition between a continent and the adjacent ocean basin floor -Atlantic-thick layers of undisturbed sediment cover the continental margin. -has very little volcanic or earthquake activity. This is because the continental margins in the Atlantic Ocean are not associated with plate boundaries, unlike the Pacific Ocean.

6. In the Pacific Ocean, where plate boundaries converge, oceanic crust is plunging beneath continental crust in a subduction zone. This force results in a narrow continental margin that experiences both volcanic activity and earthquakes

7. Ocean Floor features If you could travel from one coast to another across the ocean floor, the first zone one would pass through upon leaving land would be the continental shelf. The continental shelf is the gently sloping submerged area extending from the shoreline. This shelf is almost nonexistent on some shorelines.

8. However, on other shorelines in the world, the continental shelf can extend outwards as much as 1500 kilometers. On average, the shelf is about 80 kilometers wide 130 meters deep at it’s seaward edge. The average steepness of the drop is only about 2 meters per kilometer drop; a slope so slight that the human eye can barely perceive it.

9. Continental shelves have political and economic significance as well. Continental shelves contain important resources such as mineral deposits, oil and natural gas deposits, and enormous sand and gravel deposits. The waters of the continental shelf also contain important fishing grounds, which are a significant source of food.

10. Continental Slope: Marking the seaward edge of the continental shelf is the continental slope. The slope is steeper than the shelf and it marks the transition from continental crust to oceanic crust. Although the steepness of the continental slope varies from location to location; the average slope is 5 degrees. In some places, the slope can exceed 25 degrees. The continental slope is a relatively narrow feature, averaging only about 20 kilometers in width.

11. Deep, steep sided valleys known as submarine canyons are cut into the continental slope. These canyons may extend to the ocean basin floor. Most information suggest that submarine canyons are formed by erosion, at least in part, by turbulent underwater currents

12. Turbidity currents are occasional movements of dense sediment-rich water down the continental slope. They are created when sand and mud on the continental shelf are disturbed, perhaps by an earthquake, and become suspended in the water.

13. Because the muddy water is denser than sea-water, it flows down the slope. As it flows down, it erodes the bank away, accumulating more sediment, and eventually cuts these deep canyons into the shelf’s surface. Erosion from these muddy torrents over time is believed to be the major force behind the carving of these large canyons.

14. Narrow continental margins, such as the one along the California coast, are marked with numerous submarine canyons created by runoff sediment from the land. Turbidity currents known to be an important mechanism of sediment transport in the ocean. erode submarine canyons and deposit sediments on the deep-ocean floor.

15. In regions where trenches do not exist, the steep continental slope merges into a more gradual incline known as the continental rise. Here the steepness of the slope drops to about 6 meters per kilometer. Where the width of the continental slope averages only about 20 kilometers wide, the continental rise may be hundreds of kilometers wide. Continental rise

16. What are the three major zones of the ocean

17. Between the continental margin and mid-ocean ridge includes deep ocean trenches, very flat areas known as abyssal plains, and tall volcanic peaks called seamounts and guyots.

18. Deep Ocean Trenches long, narrow creases in the ocean floor that form the deepest parts of the ocean.

19. Abyssal Plains: deep, extremely flat features. In fact, these regions may be the most level areas on Earth. have thick accumulations of fine sediment that have buried an otherwise rugged sea floor. sediments in abyssal plain are carried out there by turbidity currents found in all oceans of the world. Atlantic Ocean has the most extensive abyssal plains because it has few trenches to catch sediment carried down the continental slope.

20. Seamounts and guyots: submerged volcanic peaks that dot the ocean floor found on the floors of all oceans. However, the greatest number can be found in the Pacific. Some can be found forming at volcanic hot spots such as the Hawaiian-Emperor Seamount chain.

21. Once underwater volcanoes reach the surface, they form islands. Over time, running water and wave action erode these islands to near sea-level. Over millions of years, these islands gradually sink below sea-level. This process occurs as the moving plate carries the island away from the elevated oceanic ridge or hot spot where they originated. These once active flat-topped but now submerged structures are called guyots.

22. locatednear the center of most ocean basins. is an interconnected system of underwater mountains that have developed on newly formed ocean crust. This system is the longest topographic feature on Earth running 70,000 kilometers around the world’s oceans.

23. A high amount of volcanic activity takes place along mid-ocean ridges. This activity is associated with sea-floor spreading. Sea-floor spreading occurs where divergent plate boundaries are moving apart from each other. New ocean is formed at mid-ocean ridges as magma rises between diverging plates and cools.

24. Hydrothermal vents form along mid-ocean ridges. zones where mineral-rich water, heated by the hot, newly formed oceanic crust, escapes through cracks in the oceanic crust into the water. As the super-heated mineral-rich water comes in contact with the cold water, minerals containing metals such as sulfur, iron, copper, and zinc precipitate out and are deposited.