Sea Floor Spreading

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What is sea floor spreading?
-->Sea-floor spreading is the process in which the ocean floor is extended when two plates move apart. As the plates move apart, the rocks break and form a crack between the plates. Earthquakes occur along the plate boundary. Magma rises through the cracks and seeps out onto the ocean floor like a long, thin, undersea volcano. library.thinkquest.org/17457/platetectonics/4.php
What are some of the major land forms that are created from plate movement?
-->A long chain of mountains forms gradually on the ocean floor as magma piles up along the crack. This chain is called an oceanic ridge. library.thinkquest.org/17457/platetectonics/4.php
How were the Mariana Islands formed?
-->A theory known as plate tectonics presumes that the Asian continent and the North and South American continents are moving and that the Lithosphere (crust) of the continents are composed of different material. The edge of these plates are believed to be moving in such a manner that one moves under the other and the cataclysmic forces that result push material upward to form islands. www.cnmi-guide.com/history/formation
What evidence exists today that the plates are still moving and that the islands are ancient volcanoes?
-->Plate tectonics is a theory of geology that has been developed to explain the observed evidence for large scale motions of the Earth's lithosphere. That facts that the fitting together of the coasts of the continents on the opposite sides of the Atlantic Ocean, the similarity of geologic formations and fossils found on the opposite sides, a geologically active mid-ocean ridge running along the central Atlantic between the opposite coasts, bottom sediments that get thicker the farther one travels from the ridge, and rocks on the sea floor on one side of the ridge show magnetic bands that are mirror images of rocks found on the opposite side of the ridge. en.wikipedia.org/wiki/Plate_tectonics#Plate_tectonic_theory
What is an atoll?
-->An atoll is an island of coral that encircles a lagoon partially or completely. Darwin (an English Naturalist) reasoned that a fringing coral reef surrounding a volcanic island in the tropical sea will grow upwards as the island subsides, becoming an "almost atoll" (barrier reef island). The fringing reef becomes a barrier reef for the reason that the outer part of the reef maintains itself near sea level through biotic growth, while the inner part of the reef falls behind, becoming a lagoon because conditions are less favorable for the corals and calcareous algae responsible for most reef growth. In time, subsidence carries the old volcano below the ocean surface, but the barrier reef remains. At this point, the island has become an atoll. http://en.wikipedia.org/wiki/Atoll
en.wikipedia.orgwikiAtoll
Why are atolls mainly found on the Pacific?-->Atolls are the product of the growth of tropical marine organisms, so these islands are only found in warm tropical waters. Volcanic islands located beyond the warm water temperature requirements of reef building organisms become seamounts as they subside and are eroded away at the surface. An island that is located where the ocean water temperatures are just sufficiently warm for upward reef growth to keep pace with the rate of subsidence is said to be at the Darwin Point.http://en.wikipedia.org/wiki/Atoll