Hot Spots

21 Aug 2017

At ... Rice University geophysicists have developed a method that uses the average motion of hot spots to determine how fast plates are moving. Hot spots are thought to lie along plate boundaries - but not universally as some hot spots occur inside plates (rather than at margins). What does this mean?

Although hot spots along the plate margin of the Naqzca Plate (west of Chile) seem to fit the uniformitarian model readily, so it is thought, the Hawaian islands hot spot may not do so. Hot spots are areas where magma is theorised to push up from deep Earth (the Mantle) and form volcanoes - and as plates move they are thought to create chains of volcanoes (in areas such as the Pacific rim of fire). The team of geophysicists have confirmed groups of hot spots can be used to determine how fast tectonic plates moved (by modeling their results). They found hot spots moved slowly enough to be used as a reference frame in models on how plates move relative to the deep mantle. Or that is what is alleged. The research will therefore be used not just in plate motion in the modern world but also plate motion in the geologic past.

Hot spots are thought to be the tops of mantle plumes and it now seems the plumes can continually move around over periods of time - as plates are imagined to move around. So, not only do we have volcanoes moving but so too do the plumes that feed them move, it is now thought. Evidence of plates mvement is also connected to the volcanic chains and islands, as in volcanic activity. Plate movement is alleged to form mountains on continental land areas, and conversely, mountains on the floor of oceans, as well as creating islands and seamounts. A volcano forms on a plate above a mantle plume and as the plate moves it gives birth to a series of volcanoes - or chain. The interesting question here might be if mantle plumes and volcanoes are moving is there any reason to have plates also moving around?

It seems 7 of the 10 plates they analysed with the new methodology, in order to ascertain motion rate, they found measured motion to be zero. Nothing at all. The other 3 plates (actually continental plates in Euroasia, N America and part of Africa (the Nubian plate) were moving just 4 to 6 millimetres a year. The movement of these 10 plates was then averaged - at around 4mm a year (even though movement of the 3 plates may only have been as low as 1mm a year). That is much slower than plates are thought to move. Next step was to amalgamate the new evidence into existing models of Plate Tectonics - and hey presto (get ready for a lot of new papers). The use of averaging has some similarities with climate science. There is actually an interesting post on averaging at ... which is a big of an eye opener (but have same methods have been used to level out the modelling of Plate movement?).

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