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Plates and Types of Crust
The earth's crust is divided up into a series of slabs of crusts known asplates. These plates consist of two different types of crust: continental crust and oceanic crust. There are important differences between the two types. Oceanic crust is constantly being created and destroyed, it is therefore younger than continental crust and its higher density means that it can be subducted and destroyed. As continental crust is ligher with a lower average density, it is permanent and cannot sink. It is also much older and thicker, reaching up to 70km under mountains. In terms of rock type, continental crust is mainly granite, whereas oceanic crust is mainly made up of basalt.
Plate Movements and Convection Currents
The earth's tectonic plates are in motion, moving like giant 'rafts' on top of the semi-molten mantle below. However this movement is slow and rates vary from less than 2.5cm /yr to over 15cm/yr.
The movement of the earth's crustal plates is believed to be due toconvection currents which occur in the semi-molten mantle. These convection currents are created by heat from within the earth - much of which is generated by radioactive decay in the core.
So how do convection currents cause plate movements? As 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)
Follow up links:
The Earth's Crust in Motion - an excellent page from St Vincent's College - exploring the nature of the crust and its movement due to convection currents - well worth a read!
A simple animation of convection and the resulting movement of plates
A clear and detailed animation of convection currents in the mantle
An animation of convection in the mantle (Exploring Earth)
The Mantle A good overview of the characteristics and influence of the mantle in tectonics
Key terms check:
Tectonic plate - individual slab of the earth's crust
Convection Current - transfer of heat throughout the mantle resulting in the rising and falling motion of semi-molten rock
Mantle - the area between the crust and the earth's core the majority of which is in a semi-molten state
What else can I help you with?
In which earth layer does crustal plate movement occur because of convection cells?
Crustal plate movement due to convection cells occurs in the asthenosphere, which is a semi-fluid layer beneath the lithosphere. The heat-driven convection currents in the asthenosphere cause the overlying crustal plates to move and interact with each other.
Describe how convection currents might be the cause of plate tectonics?
Convection currents in the mantle cause the movement of tectonic plates. Heat from the Earth's core creates rising currents of molten mantle material, which pushes the plates apart at mid-ocean ridges. As the plates cool, they sink back into the mantle at subduction zones, completing the cycle of plate movement driven by convection currents.
What is convection and how does it cause plates to move?
Convection is the transfer of heat through the movement of a fluid, such as a liquid or gas. In the Earth's mantle, hot magma rises near the core, is cooled near the surface, and then sinks back down. This continuous cycle of rising and sinking creates convection currents that drag tectonic plates along with them, causing the plates to move.
What is the convection current hypothesis?
The convection current hypothesis supposes that convection currents in the Earth's Mantel (the zone below the surface/crust and above the Earth's core) cause the movement of the tectonic plates (plates that make up the surface/crust of the Earth and shift/move on a grand time scale).
What layer of the earth has convection currents that cause tectonic plates to move?
The asthenosphere, which is a partially molten layer in the upper mantle, has convection currents that cause tectonic plates to move due to the heat-driven circulation of rock material. These convection currents are responsible for the continuous motion of tectonic plates on the Earth's surface.
Do convection current in oceans cause tectonic plates to move?
No, convection currents in the upper mantle cause tectonic plates to move.
What is the behavior of the crustal plates in relation to the asthenosphere?
The crustal plates move on the semi-fluid asthenosphere due to convection currents in the mantle. These convection currents cause the plates to either separate, collide, or slide past each other, leading to various geological phenomena like earthquakes, volcanic activity, and mountain formation.
What is the cause of the Italian earthquake 2009?
All earthquakes have the same cause, which is the movement of the Earth's crustal plates resulting from convection currents in the magma upon which they float.
In which earth layer does crustal plate movement occur because of convection cells?
Crustal plate movement due to convection cells occurs in the asthenosphere, which is a semi-fluid layer beneath the lithosphere. The heat-driven convection currents in the asthenosphere cause the overlying crustal plates to move and interact with each other.
How does the crustal plates moves?
by bubbling hot magma in the earth's inner core, erupting from volcanoes and causing earthquakes which cause the crustal plates to move.
How plate tectonics move?
== == The main features of plate tectonics are: * The Earth's surface is covered by a series of crustal plates. * The plates are composed of crustal rock and solid upper mantle which is called the lithosphere. * Plates are composed of continental and oceanic crust. * The oceanic crusts are continually moving, spreading from the center, sinking at the edges, in a process of recycling. * Rising legs of convection currents beneath the plates create additional plate material at mid-ocean ridges, sinking legs of convection currents swallow old crustal plates at subduction zones. * The heat driving the convection currents is from radioactive decay of material within the Earth and from residual heat from accretion processes during Earth's formation. Convection cells in the magma of the outer core pull the earth's tectonic plates along the surface. These plates can collide and cause earthquakes.
What caused continental drift?
volcanos, mountains
What activity in the magma causes crustal plate movement?
The movement of magma beneath the Earth's crust can create convection currents, which push and pull on the crustal plates above. This movement can cause the plates to shift and collide, leading to processes such as subduction, where one plate is forced beneath another, or seafloor spreading, where new crust is formed along mid-ocean ridges.
How convection currents might be the cause of plate tectonics?
A convection current, in simple terms, is a cycle that keeps bringing the cool stuff down and the hot stuff up. This current could move the plates as they ride on top of the hot magma.
Describe how convection currents might be the cause of plate tectonics?
Convection currents in the mantle cause the movement of tectonic plates. Heat from the Earth's core creates rising currents of molten mantle material, which pushes the plates apart at mid-ocean ridges. As the plates cool, they sink back into the mantle at subduction zones, completing the cycle of plate movement driven by convection currents.
Can the convection currents in the mantle cause the movement of crustal plates?
Yes, the upper mantle does move the crustal plate. There are actually many different plates, each holding a continent, ocean, or both. They can move these plates because of a thing called convection currents. They are the circular motion of magma getting hotter and cooling off. These move the plates together, under each other, or apart.
What is convection and how does it cause plates to move?
Convection is the transfer of heat through the movement of a fluid, such as a liquid or gas. In the Earth's mantle, hot magma rises near the core, is cooled near the surface, and then sinks back down. This continuous cycle of rising and sinking creates convection currents that drag tectonic plates along with them, causing the plates to move.
