Why do trees seem to resist more to tsunamis than houses? Why does a boat at sea experience a tsunami differently from a boat near the shore? Volcanoes All About Volcanoes What is the difference between magma and lava? Is lava always liquid? What does a magma chamber look like? What are the largest eruptions in the world? Are earthquakes and volcanic eruptions related?
Where can we find volcanoes on earth? Miscellaneous Miscellaneous Why are there mass extinctions? How did life appear on earth? How does photosynthesis work? What is GPS? What is gravity? What is the big bang? How do we know the age of the earth? What about the age of the solar system? Why do tectonic plates move? Eventually all that remains of the island is a ring of coral reef. An atoll is a ring-shaped coral reef or group of coral islets that has grown around the rim of an extinct submerged volcano forming a central lagoon Fig.
Atoll formation is dependent on erosion of land and growth of coral reefs around the island. Coral reef atolls can only occur in tropical regions that are optimal for coral growth. The main Hawaiian Islands will all likely become coral atolls millions of years into the future. The older Northwestern Hawaiian Islands, many of which are now atolls, were formed by the same volcanic hot spot as the younger main Hawaiian Islands.
This document may be freely reproduced and distributed for non-profit educational purposes. Skip to main content. Search form Search. Join The Community Request new password. Main menu About this Site Table of Contents. Continental Movement by Plate Tectonics. MS-ESS Analyze and interpret data on the distribution of fossils and rocks, continental shapes, and seafloor structures to provide evidence of the past plate motions. HS-ESS Evaluate evidence of the past and current movements of continental and oceanic crust and the theory of plate tectonics to explain the ages of crustal rocks.
The content and activities in this topic will work towards building an understanding of how the surface of the earth has changed over time by the process of plate tectonics. The motion of plates can be described in four general patterns: Collision : when two continental plates are shoved together Subduction : when one plate plunges beneath another Fig. Voice of the Sea. Simulate tectonic plate spreading by modeling convection currents that occur in the mantle. Practices of Science.
Further Investigations. Activity: Modeling Plate Spreading. Special Features:. Representative Image:. Further Investigations: What is an Invertebrate? Question Set: What is a Mammal? Further Investigations: What is a Mammal? Share and Connect. We invite you to share your thoughts, ask for help or read what other educators have to say by joining our community.
Partner Organizations. As the semi-molten rock in the mantle is heated it becomes less dense than its surroundings and rises. As it reaches the crust above, it spreads out carrying the plates above with it. As the semi-molten rock then cools, it gradually sinks back down to be re-heated see diagram above. Another explanation for plate movement is ridge push. Newly-formed plates at oceanic ridges constructive plate margins are warm, and so have a higher elevation at the oceanic ridge than the colder, more dense plate material further away; gravity causes the higher plate at the ridge to push away causing the plates to move away from each other.
Convection currents, slab push and slab pull are believed to be responsible for tectonic plate movement.
Additionally, at destructive plate margins the denser, oceanic plate sinks into the mantle under the influence of gravity, which pulls the rest of the plate along with it. This is known as slab pull. Wegener first presented his idea of continental drift in , but it was widely ridiculed and soon, mostly, forgotten. Wegener never lived to see his theory accepted—he died at the age of 50 while on an expedition in Greenland.
Only decades later, in the s, did the idea of continental drift resurface. Those advances included seismometers used to monitor ground shaking caused by nuclear testing and magnetometers to detect submarines. With seismometers, researchers discovered that earthquakes tended to occur in specific places rather than equally all over Earth. When these plates press together and then move suddenly, energy is released in the form of earthquakes.
Plate tectonics also explains the stripes of rock on the seafloor with alternating magnetic properties: As buoyant, molten rock rises up from deep within Earth, it emerges from the space between spreading tectonic plates and hardens, creating a ridge. Therefore, the theory of plate tectonics is more complete. It has gained widespread acceptance among scientists.
This shift from one theory to another is an example of the scientific process: As more observations are made and measurements are collected, scientists revise their theories to be more accurate and consistent with the natural world. Because tectonic plates move very slowly—only a few centimeters per year, on average—it takes a long time to observe changes. That is because as Africa continues to migrate north it will collide with Europe, a collision that will probably create a Himalaya-scale mountain range.
However, Christopher Scotese, one of the scientists who developed these simulations, cautions that it is difficult to predict exactly how the continents will be arranged in millions of years.
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