SeaFloor Spreading

Ocean Floor Features Identify the features below using the word:WORD BANK: (spelling counts)mid-ocean ridgeoceanic crustocean trench mid-ocean ridge ocean trench oceanic crust Age of Rock Identify where the rock is the youngest and where it is the oldest in the following figure.WORD BANK: (spelling counts)youngestoldest youngest oldest Sort the descriptions into the correct categories: Mid-Ocean Ridge New crust created Underwater volcano chain Makes igneous rock Thinner and less dense rock Ocean Trench Old crust sinks back into the Earth Also known as a subduction zone Igneous rock may be covered by several layers of sedimentary rock and contain fossils Thicker and more dense rock Fill-in the blanks below: Some minerals in volcanic rocks develop a slight magnetism in alignment with Earth’s magnetic field at the time of their formation. Also, scientists have discovered that the polarity of Earth’s magnetic field has periodically reversed and the North Magnetic Pole becomes the South Magnetic Pole and vice versa. Putting these facts together provides additional support for plate tectonics.The ancient magnetism, present in rocks on the ocean floor can be used to determine the rate at which the plates are separating and, consequently, the time when they began to separate. Where plates separate along the mid-ocean ridge, magma from the mantle rises to the surface and creates a new ocean floor. As the magma cools, the magnetic minerals in the molten rock line up with the prevailing magnetic field. As the plates continue to separate and Earth’s magnetic field reverses polarity, new material forming at the ridge is magnetized in an opposite (or reversed) direction. True or False: the age of the normal and reverse polarities recorded on the ocean floor are mirror image on both sides of the ocean floor. True False Building Vocabulary Using the word bank provided, fill in the blank to complete each statement.Word Bank (spelling counts):mid-ocean ridgesea-floor spreadingdeep-ocean trenchsubduction A canyon on the ocean floor at which the crust bends downward is called a(n)? deep-ocean trench The process that continually adds new material to the ocean floor is called? sea-floor spreading The process by which the ocean floor sinks into the mantle is known as? subduction A chain of underwater mountains along which sea-floor spreading occurs is a(n)? mid-ocean ridge