Seafloor Spreading PDF

SEAFLOOR SPREADING Ma’am Jam ☺  FUN FACT Did you know that??? “The ocean basins cover the largest area of the earth’s surface.” OCEAN BASINS It is anywhere on Earth that is covered by seawater. Geologically, ocean basins are large geologic basins that...

SEAFLOOR SPREADING Ma’am Jam ☺  FUN FACT Did you know that??? “The ocean basins cover the largest area of the earth’s surface.” OCEAN BASINS It is anywhere on Earth that is covered by seawater. Geologically, ocean basins are large geologic basins that are below sea level.  DIFFERENT FEATURES AND STRUCTURES STRUCTURE / FEATURES DEFINITION Partly shallow extension of the Continental shelf continent underwater. Transition zone of continental shelf and Continental deep ocean floor. It starts from slope continental crust to oceanic crust. It is where the ocean begins. The Continental rise continental margin starts from continental shelf up to continental rise.  DIFFERENT FEATURES AND STRUCTURES STRUCTURE / FEATURES DEFINITION The flattest part of the ocean. 50 % of the earth’s Abyssal plain surface is being covered by this plain. It’s a piece of land floating up in the middle of the Island sea and a part of the ocean basin that extends up from the ocean floor. Trench It is the deepest part of the ocean.  DIFFERENT FEATURES AND STRUCTURES STRUCTURE / FEATURES DEFINITION The seafloor mountain system which is situated in the middle of Mid-oceanic the ocean basin. It is where ridge upwelling of magma happens which causes the sea floor to spread. EVOLUTION OF OCEAN BASIN WILSON CYCLE Explains the process of the opening (beginning) and the closing (end) of an ocean which is driven by Plate Tectonics. This process is named after the Canadian Geophysicist J. Tuzo Wilson (1908-1993). 01. EMBRYONIC DESCRIPTION EXAMPLE: Motion: Uplift Features: Complex East African system of linear rift Rift Valleys valleys on continent 02. JUVENILE DESCRIPTION EXAMPLE: Motion: Divergence (Spreading) Red Sea Features: Narrow seas with matching coasts 03. MATURE DESCRIPTION EXAMPLE: Motion: Divergence Atlantic and (Spreading) Arctic Features: Ocean Oceans basin with continental margins 04. DECLINING DESCRIPTION EXAMPLE: Motion: Convergent (Subduction) Pacific Features: Islands Ocean arcs and trenches around basin edge 05. TERMINAL DESCRIPTION EXAMPLE: Motion: Convergent (Collision and Uplift) Mediterran Features: Narrow, ean Sea irregular seas with young mountains 06. SUTURING DESCRIPTION EXAMPLE: Motion: Convergence and Uplift Himalayas Features: Young to Mountains mature mountain belts SONAR (Sound Navigation and Ranging) It is helpful for exploring and mapping the ocean because sound waves travel farther in the water than do radar and light waves.  2 TYPES OF SONAR 01 02 ACTIVE PASSIVE It sends out sound waves in It is a listening device only; pulses; scientists then measure sound waves produced by the time it takes these pulses to another source are received travel through the water, reflect and changed into electrical off of an object, and return to signals for display on a the ship. monitor. HARRY HAMMOND HESS In 1960, He explained how the convection currents in the Earth’s interior make the seafloor spread. He envisaged that oceans grew from their centres, with molten material (basalt) oozing up from the Earth's mantle along the mid ocean ridges. This created new seafloor which then spread away from the ridge in both directions. CONVECTION CURRENTS It carry heat from the molten materials in the mantle and core towards the lithosphere. In places where convection currents rise up towards the crust's surface, tectonic plates move away from each other in a process known as seafloor spreading. In this recycling process which was later named as seafloor spreading, the magma moves up from the mantle and erupts as pillow lava. This forms new oceanic crust at the ridge. Then, as new oceanic crust form, it pushes the older crust aside. This crust eventually subducts at the deep ocean trenches and melts back into the mantle. Then the seafloor spreading continues as a “recycling” process. SEAFLOOR SPREADING The formation of new areas of oceanic crust, which occurs through the upwelling of magma at midocean ridges and its subsequent outward movement on either side. Three evidence that support the idea that seafloor is continuously spreading 1. 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. Three evidence that support the idea that seafloor is continuously spreading 2. 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; Three evidence that support the idea that seafloor is continuously spreading 3. 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