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Hub AI
Intraplate volcanism AI simulator
(@Intraplate volcanism_simulator)
Hub AI
Intraplate volcanism AI simulator
(@Intraplate volcanism_simulator)
Intraplate volcanism
Intraplate volcanism is volcanism that takes place away from the margins of tectonic plates. Most volcanic activity takes place on plate margins, and there is broad consensus among geologists that this activity is explained well by the theory of plate tectonics. However, the origins of volcanic activity within plates remains controversial.
Mechanisms that have been proposed to explain intraplate volcanism include mantle plumes; non-rigid motion within tectonic plates (the plate model); and impact events. It is likely that different mechanisms accounts for different cases of intraplate volcanism.
A mantle plume is a proposed mechanism of convection of abnormally hot rock within the Earth's mantle. Because the plume head partly melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, and large igneous provinces such as the Deccan Traps and Siberian Traps. Some such volcanic regions lie far from tectonic plate boundaries, while others represent unusually large-volume volcanism near plate boundaries.
The hypothesis of mantle plumes has required progressive hypothesis-elaboration leading to variant propositions such as mini-plumes and pulsing plumes.
Mantle plumes were first proposed by J. Tuzo Wilson in 1963[non-primary source needed] and further developed by W. Jason Morgan in 1971. A mantle plume is posited to exist where hot rock nucleates[clarification needed] at the core-mantle boundary and rises through the Earth's mantle becoming a diapir in the Earth's crust. In particular, the concept that mantle plumes are fixed relative to one another, and anchored at the core-mantle boundary, would provide a natural explanation for the time-progressive chains of older volcanoes seen extending out from some such hot spots, such as the Hawaiian–Emperor seamount chain. However, paleomagnetic data show that mantle plumes can be associated with Large Low Shear Velocity Provinces (LLSVPs) and do move.
Two largely independent convective processes are proposed:
The plume hypothesis was studied using laboratory experiments conducted in small fluid-filled tanks in the early 1970s. Thermal or compositional fluid-dynamical plumes produced in that way were presented as models for the much larger postulated mantle plumes. Based on these experiments, mantle plumes are now postulated to comprise two parts: a long thin conduit connecting the top of the plume to its base, and a bulbous head that expands in size as the plume rises. The entire structure is considered to resemble a mushroom. The bulbous head of thermal plumes forms because hot material moves upward through the conduit faster than the plume itself rises through its surroundings. In the late 1980s and early 1990s, experiments with thermal models showed that as the bulbous head expands it may entrain some of the adjacent mantle into the head.
The sizes and occurrence of mushroom mantle plumes can be predicted easily by transient instability theory developed by Tan and Thorpe. The theory predicts mushroom shaped mantle plumes with heads of about 2000 km diameter that have a critical time[clarification needed] of about 830 Myr for a core mantle heat flux of 20 mW/m2, while the cycle time[clarification needed] is about 2 Gyr. The number of mantle plumes is predicted to be about 17.
Intraplate volcanism
Intraplate volcanism is volcanism that takes place away from the margins of tectonic plates. Most volcanic activity takes place on plate margins, and there is broad consensus among geologists that this activity is explained well by the theory of plate tectonics. However, the origins of volcanic activity within plates remains controversial.
Mechanisms that have been proposed to explain intraplate volcanism include mantle plumes; non-rigid motion within tectonic plates (the plate model); and impact events. It is likely that different mechanisms accounts for different cases of intraplate volcanism.
A mantle plume is a proposed mechanism of convection of abnormally hot rock within the Earth's mantle. Because the plume head partly melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, and large igneous provinces such as the Deccan Traps and Siberian Traps. Some such volcanic regions lie far from tectonic plate boundaries, while others represent unusually large-volume volcanism near plate boundaries.
The hypothesis of mantle plumes has required progressive hypothesis-elaboration leading to variant propositions such as mini-plumes and pulsing plumes.
Mantle plumes were first proposed by J. Tuzo Wilson in 1963[non-primary source needed] and further developed by W. Jason Morgan in 1971. A mantle plume is posited to exist where hot rock nucleates[clarification needed] at the core-mantle boundary and rises through the Earth's mantle becoming a diapir in the Earth's crust. In particular, the concept that mantle plumes are fixed relative to one another, and anchored at the core-mantle boundary, would provide a natural explanation for the time-progressive chains of older volcanoes seen extending out from some such hot spots, such as the Hawaiian–Emperor seamount chain. However, paleomagnetic data show that mantle plumes can be associated with Large Low Shear Velocity Provinces (LLSVPs) and do move.
Two largely independent convective processes are proposed:
The plume hypothesis was studied using laboratory experiments conducted in small fluid-filled tanks in the early 1970s. Thermal or compositional fluid-dynamical plumes produced in that way were presented as models for the much larger postulated mantle plumes. Based on these experiments, mantle plumes are now postulated to comprise two parts: a long thin conduit connecting the top of the plume to its base, and a bulbous head that expands in size as the plume rises. The entire structure is considered to resemble a mushroom. The bulbous head of thermal plumes forms because hot material moves upward through the conduit faster than the plume itself rises through its surroundings. In the late 1980s and early 1990s, experiments with thermal models showed that as the bulbous head expands it may entrain some of the adjacent mantle into the head.
The sizes and occurrence of mushroom mantle plumes can be predicted easily by transient instability theory developed by Tan and Thorpe. The theory predicts mushroom shaped mantle plumes with heads of about 2000 km diameter that have a critical time[clarification needed] of about 830 Myr for a core mantle heat flux of 20 mW/m2, while the cycle time[clarification needed] is about 2 Gyr. The number of mantle plumes is predicted to be about 17.