This event will cause the mantle to sink down due to the pull of gravity. Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy. Heat energy is transferred from hot places to cooler places by convection.
Liquids and gases expand when they are heated. The denser cold liquid or gas falls into the warm areas. Convection currents play a role in the circulation of fluids.
Convection currents are the result of differential heating. Lighter less dense , warm material rises while heavier more dense cool material sinks. Convection also plays a role in the movement of deep ocean waters and contributes to oceanic currents. The primary sources of thermal energy for mantle convection are three: 1 internal heating due to the decay of the radioactive isotopes of uranium, thorium, and potassium; 2 the long-term secular cooling of the earth; and 3 heat from the core. This hot water rises and cooler water moves down to replace it, causing a circular motion.
There are two types of convection: natural convection and forced convection. Natural convection is produced by density differences in a fluid due to temperature differences e. Global atmospheric circulation and local weather phenomena including wind are due to convective heat transfer. Convection is the circular motion that happens when warmer air or liquid — which has faster moving molecules, making it less dense — rises, while the cooler air or liquid drops down.
Convection is a major factor in weather. That current can result in wind, clouds, or other weather. A space heater is a classic convection example. As the space heater heats the air surrounding it near the floor, the air will increase in temperature, expand, and rise to the top of the room.
This forces down the cooler air so that it becomes heated, thus creating a convection current. During convection, cooler water or air sinks, and warmer water or air rises. How fast does the earth rotate per second? How fast is the earth traveling along its orbit? How fast does the earth rotate on its axis? How fast does the earth rotate in one minute? What is the formula to determine this?
See all questions in The Earth. Impact of this question views around the world. Some shield volcanoes, such as the islands in the Hawaiian archipelago, began forming on the ocean floor over a hot spot. Each shield volcano grows slowly with repeated eruptions until it reaches the surface of the water to form an island Fig. Almost all of the mid-Pacific and mid-Atlantic ocean basin islands formed in a similar fashion over volcanic hot spots.
Over millions of years as the tectonic plate moves, a volcano that was over the hot spot moves away, ceases to erupt, and becomes extinct Fig. Islands can erode through natural processes such as wind and water flow. 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?
What Causes Metamorphic Rocks to Form? How to Dissolve Rock Salt. What Are the Doldrums? How to Make a Sodium Silicate Solution. Hadley Cell Effects. How is the Sun Nuclear Energy? How Does Wind Affect Weather?
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