Ocean Basin, Trenches, and Plate Movement.pptx

learn about ocean basin, trenches, and plate movement. this topic is part of the lesson covered in earth science.

1. OCEAN BASIN, TRENCHES, GROUP 3 AND PLATE MOVEMENT

2. INTRODUCTION Through most of geologic time, probably extending back 2 billion years ago, the ocean basins have grown and have Crustal plates move gradually and converge at their boundaries. These boundaries are common areas of tectonic activity which causes the deformation of the Earth’s crust. been consumed as plate tectonics continued on Earth.

3. SONAR It is an instrument that accurately determines the time between the emission of a strong acoustic pulse and the detection of its echo.

4. Plates can spread apart by moving away from each other. This creates gas where hot molten rock, called magma from the Earth’s mantle walls up. magma seeps through the gaps solidifies as it cools creates a new layer of ocean crust

5. The mid-ocean ridge is the most extensive chain of mountains on Earth, stretching nearly 65,000 kilometers (40,390 miles) and with more than 90 percent of the mountain range lying underwater, in the deep ocean with an average water depth to the top of the ridge of 2,500 meters (8,200 feet).

6. Mid-ocean ridges occur along divergent plate boundaries. As the plates separate, molten rock rises to the seafloor, producing enormous volcanic eruptions of basalt. The speed of spreading affects the shape of a ridge: slow-spreading rates result in steep, irregular topography while fast-spreading rates produce much wider profiles and more gentle slopes.

7. Around 80 mya, North America was being separated from Europe, which gave rise to the Mid-Atlantic Ridge, measuring 10,000 miles lengthwise. It was found in the 19th century when the first trans-Atlantic cable was laid. Running along the center of the Atlantic Ocean, the Mid-Atlantic Ridge is the slow-spreading type , growing at an annual rate of 2 to 5 centimetres or 10 mm to 150 mm a year. EXAMPLE

8. The East Pacific Rise is situated along the floor of the Pacific Ocean. It is fast spreading , at a rate of 6 to 16 cm a yr. As the process is fast, no valley has been formed in the Pacific. It contains only a volcanic summit, smaller than the Atlantic rift valley. Most of the rise lies over 3200 km from the South American coast and rises around 1800 to 2700 meters above the ocean floor. EXAMPLE

9. An abyssal plain is another raised featured found on the ocean basins. It is defined as small elevated landform that rises from the great depths of the ocean. The word '' abyss '' which means very deep will help you remember the term abyssal hill. An abyssal hill has simply defined edges but is relatively small, generally not higher than 500 feet and few miles wide.

10. Abyssal plain

11. Abyssal hill

12. Ocean trenches are long narrow, steep-sided depressions found on the ocean floor that contain the greatest depths in the ocean Ocean Trenches

13. Trenches are located in subduction zones at or near a convergent boundary, continental crust, and/ or volcanic islands. Ocean Trenches

14. Ocean Trenches

15. Ocean Trenches

16. There are 26 oceanic trenches in the world: 3 in the Atlantic Ocean, 1 in the India Ocean and 22 in the Pacific Ocean. Ocean trenches mark the transition between continents and ocean basin, especially in the Pacific. Ocean Trenches

17. Ocean Floor The ocean floor, or seabed, is a term used to describe the top layer of oceanic crust found on the bottom of the ocean just above the mantle. It is found at the base of the continental rise in water 4000 to 6000 meters deep. The ocean floor accounts for nearly 30% of the Earth’ssurface.

18. Ocean Floor

19. I. Origins & Processes II. Features III. Exploration & Discovery Ocean Floor

20. Ocean Floor I: Seafloor Spreading a geologic process in which tectonic plates split apart from each other. Seafloor spreading and other tectonic activities are the result of mantle convection . Seafloor spreading occurs at divergent plate boundaries .

21. Ocean Floor I: Mantle convection the very slow creeping motion of Earth's solid silicate mantle as convection currents carrying heat from the interior to the Earth's surface. the processes are found in between the lithosphere and the topmost part of the asthenosphere in relation to the ocean floor alone as what is being discussed.

22. Ocean Floor II: Features Continental Shelf Continental Slopes Continental Rise Abyssal Plains Abyssal Hill Mid-Ocean Ridges Seamounts Deep Ocean Trenches Volcanic Islands

23. Ocean Floor III: Exploration & Discovery The first scientific expedition to explore the world’s oceans and seafloor was the Challenger Expedition, from 1872 to 1876, on board the British three-masted warship HMS Challenger.

24. Ocean Floor III: Exploration & Discovery 1872-1876 : The HMS Challenger, led by Charles Wyville Thomson, conducts the first deep sea exploration expidition. 1930 : William Beebe and Otis Barton were the first humans to reach the Deep Sea using their Bathysphere. 1960 : Jacques Piccard and Don Walsh, with the deep sea vessel Trieste , descend to the bottom of the Challenger Deep in the Mariana Trench (10740m/6.67mi)

25. Ocean Floor III: Exploration & Discovery Marie Tharp (July 30, 1930 - August 23, 2006) was an American geologist and oceanographic cartographer. in the 1950s, she collaborated with geologist Bruce Heezen to produce the scientific map of the Atlantic Ocean floor.

26. continental rise is a wide, gentle incline from a deep ocean plain (abyssal plain) to a continental slope. A continental rise consists mainly of silts, mud, and sand, deposited by turbidity flows, and can extend for several hundreds of miles away from continental margins. Continental Rise

27. Continental Rise The continental rise is found at the base of the continental slope. The depth of the rise ranges from 2,000 to 5,000 meter deep. Its width is up to 300 km wide.

28. Continental Shelf a shallow, gently sloping part of the continental crust with an average depth of 130 meters that borders the continents. The extent of this feature varies from tens of meters to a maximum width of about 1300 kilometers.

29. Continental Shelf A continental shelf is the edge of a continent lying beneath the ocean. This shelf extends from the coastline of a continent to a drop off point called the c ontinental shelf break .

30. Continental Slope The continental slope extends from the continental shelf at an average depth of 135 meters. Sloping down from the inner shallow seas to the deep ocean, the continental slope is a geological feature marking the divide between two ocean zones. In some areas the continental slope is narrow and very steep, whilst in others it is wide and has a gentle gradient.

31. OCEAN BASINS

32. Ocean basins are formed geologically of oceanic (basalt) crust, in contrast to continental (granite) crust that forms the Earth’s major land masses.

33. oceanic basin is the land surface under an ocean that includes the various topography below the water. About 70% of the planet's surface is made up of ocean basins, which are the regions that are below sea level. There are 5 major ocean basins: PACIFIC OCEAN BASIN, ATLANTIC OCEAN BASIN, INDIAN OCEAN BASIN, SOUTHERN OCEAN BASIN and ARCTIC OCEAN BASIN

34. Thus some smaller “seas” that are underlain by ocean crust and are isolated from the world ocean as separate basins, Mediterranean, Tasman, Coral, Caribbean, and the Red Seas, may be considered oceanic. By contrast, other shelf seas and gulfs are perched on continental crust (e.g., the North Sea, Arafura Sea, Baltic Sea, Yellow Sea) and are consequently distinguished on a geological basis from oceanic basins

35. MOVEMENT OF PLATES 3 TYPES OF BOUNDARIES Creates

36. CONVERGENT BOUNDARIES where plates move into one another the plate collisions can produce earthquakes, volcanic activities and crustal deformation

37. CONVERGENT BOUNDARIES OCEANIC AND COTINENTAL PLATES where the continental and oceanic plates collide the thinner and more dense oceanic plate is overridden by the thicker and less dense continental plate - SUBDUCTION a depth of about 100 miles (160 km), the materials begin to approach their melting temperatures and a process of partial melting begins - MAGMA CHAMBERS Magma chambers are less dense than the surroundings and are buoyant Ex: Nazca Plate under South America

38. CONVERGENT BOUNDARIES OCEANIC - OCEANIC PLATES where a convergent boundary occurs between two oceanic plates the older and colder plate will subduct to the younger and warmer plate because of its higher density forms deep trenches like the Mariana Trench in the North Pacific Ocean, the deepest point on Earth

39. CONVERGENT BOUNDARIES CONTINENTAL - CONTINENTAL PLATES where two thick continental plates collide both of them have a density that is much lower than the mantle, this prevents subduction The intense compression can also cause extensive folding and faulting of rocks resulting mountains Ex: Himalaya Mountains

40. DIVERGENT BOUNDARIES where plates move apart This happens when rising currents push up on the bottom of the lithosphere, lifting it and moving it along under it. This movement causes the material above to be dragged along with the current in the direction of flow. At the crest of the uplift, the overlying plate can be stretched thin and break, pulling it apart.

41. Divergent boundaries in the oceans, magma from deep in the Earth's mantle rises toward the surface and pushes apart two or more plates. Mountains and volcanoes rise along the seam. The process renews the ocean floor and widens the giant basins.

42. Divergent boundaries on land, the pull-apart is not strong enough to create a clean break through the thick plate material; instead, the two plates are pulled thin and fractured into a rift-shaped structure

43. EXAMPLE: - Divergent Plate boundary-Oceanic The Mid-Atlantic Ridge -Divergent Plate boundary-Continental The Great Rift Valley in Africa EFFECTS: - Divergent Plate boundary-Oceanic a submarine mountain range, volcanic activity in the form of fissure eruptions; shallow earthquake activity; creation of new seafloor and a widening ocean basin. -Divergent Plate boundary-Continental a rift valley; numerous normal faults bounding a central rift valley; shallow earthquake activity, volcanic activity

44. TRANSFORM PLATE BOUNDARIES - where plates move sideways in relation to each other. - is formed between two different plates, each moving away from the spreading center of a divergent plate boundary. 

45. A transform fault is the fracture zone that forms the boundary of a transform plate The San Andreas Fault in California is an example of transform boundary These boundaries don't produce spectacular features likemountains or oceans, but the halting motion often triggers large earthquakes, such as the 1906 one that devastated San Francisco.

46. THAT'S ALL. THANKS FOR LISTENING. MAG-QUIZ NA HEHE