Seafloor Spreading: Q2 2017 PDF

1 SEAFLOOR SPREADING By: Glenn C. Gambalan, RM.RN.MSN.LPT.  2 LEARNING COMPETENCY Explain how seafloor spreads (S11ES-IIf-3)2 LEARNING OBJECTIVES a. discuss the process of seafloor spreading b. explain how the convection currents in the e...

1 SEAFLOOR SPREADING By: Glenn C. Gambalan, RM.RN.MSN.LPT.  2 LEARNING COMPETENCY Explain how seafloor spreads (S11ES-IIf-3)2 LEARNING OBJECTIVES a. discuss the process of seafloor spreading b. explain how the convection currents in the earth’s interior make the seafloor spread c. describe the three evidence that seafloor is continuously spreading  3 SEAFLOOR SPREADING - A geological process by which new oceanic crust forms at mid-ocean ridges through volcanic activities and then slowly moves away from the ridges. - occurs at divergent boundaries where the tectonic plates move away from each other, resulting in the formation of new seafloor. ECHO SOUNDERS / SONAR Echo sounders produce sound waves that travel outward in all directions. The sound waves bounce off the nearest object, and then return to the ship.  FEATURES OF THE SEAFLOOR 5 A modern map of the eastern Pacific and Atlantic Oceans. Darker blue indicates deeper seas. A mid-ocean ridge can be seen running through the center of the Atlantic Ocean. Deep sea trenches are found along the west huge mountains coast of Central and South America and in and mountain the mid-Atlantic, east of the southern tip of rangers, deep South America. Isolated mountains and flat, trenches, mid featureless regions can also be spotted. oceanic ridges SEAFLOOR MAGNETISM 6 magnetometers Scientists were surprised to discover that the normal and reversed magnetic polarity of seafloor basalts creates a pattern of magnetic stripes. The seafloor has different features which includes continental shelf, continental slope, abyssal plain, mid- ocean ridge, seamount and trench. POLAR REVERSALS 7 When the north and south poles are aligned as they are now, geologists say it is normal polarity. When they are in the opposite position, they say that it is reversed polarity. MAGNETIC STRIPES 8 Scientists found that magnetic polarity in the seafloor was normal at mid-ocean ridges but reversed in symmetrical patterns away from the ridge center. This normal and reversed pattern continues across the seafloor. SEAFLOOR AGES 9 Seafloor is youngest near the mid-ocean ridges and gets progressively older with distance from the ridge. Orange areas show the youngest seafloor. The oldest seafloor is near the edges of continents or deep sea trenches. THE SEAFLOOR SPREADING HYPOTHESIS Convection currents in the mantle result in the movement of lithospheric plates. The motion and interactions of the plates can create patterns in the location of volcanoes and earthquakes that result along the plate boundaries. 12  13 PROCESSES OF SEAFLOOR SPREADING The movement of oceanic plates at divergent boundaries leads to the development of fractures in the lithosphere due to TENSIONAL STRESS.  14 PROCESSES OF SEAFLOOR SPREADING Hot basaltic magma from the mantle rises from the fractures at the spreading centers present along the crests of mid-ocean ridges..  15 PROCESSES OF SEAFLOOR SPREADING This hot magma subsequently cools down and hardens to become the new seafloor or oceanic crust primarily composed of basaltic rocks.  16 PROCESSES OF SEAFLOOR SPREADING The newly formed seafloor then slowly moves away from the ridge, and its place is taken by a newer seafloor, and the cycle repeats  17 PROCESSES OF SEAFLOOR SPREADING The older rocks move farther away from the spreading centers, whereas the comparatively younger rocks are found close to the spreading centers 18 EVIDENCES THAT THE SEAFLOOR IN CONTINUOUSLY SPREADING (a.) Evidence from molten materials (b.) Evidence from magnetic strip (c.) Evidence from drilling sample EVIDENCES THAT THE SEAFLOOR IN CONTINUOUSLY SPREADING (a.) Evidence from molten materials- rocks shaped like pillows (rock pillows) show that molten materials have erupted again and again from cracks along the mid-ocean ridge and cooled quickly. EVIDENCES THAT THE SEAFLOOR IN CONTINUOUSLY SPREADING (b.) Evidence from magnetic strip- rocks that make up the ocean floor lie in a pattern of magnetized stripes which hold a record of the reversals in magnetic field EVIDENCES THAT THE SEAFLOOR IN CONTINUOUSLY SPREADING (c.) Evidence from drilling sample – core samples from the ocean floor show that older rocks are found farther from the ridge; youngest rocks are in the mid-ocean ridge WHY DOESN’T THE EARTH GETS BIGGER AS THE SEAFLOOR SPREADS? THANK YOU