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The planet's inner heat powers plate tectonics. That heat is ebbing away as Earth ages, and this was expected to slow plate motion. A study last year by Martin Van Kranendonk at the University of New South Wales in Sydney, Australia, and colleagues measured elements concentrated by tectonic action in 3200 rocks from around the world, and concluded that plate motion has been slowing for 1.2 billion years.
Now Kent Condie, a geochemist at the New Mexico Institute of Mining and Technology in Socorro and his colleagues have used a different approach and concluded that tectonic activity is increasing. They looked at how often new mountain belts form when tectonic plates collide with one another. They then combined these measurements with magnetic data from volcanic rocks to work out at which latitude the rocks formed and how quickly the continents had moved.
Both techniques showed plate motion has accelerated. The average rate of continental collisions, and the average speed with which the continents change latitude, has doubled over the last 2 billion years (Precambrian Research, doi.org/vbv).
"We expected to find that the average speed would be slowing down with time, but we didn't get that. Both speeds were going up," says Condie. "It was a surprise."
Condie thinks the mantle's huge store of water could explain the finding. When crust sinks back into the mantle, oceanic water gets sucked down too, and although most comes back to the surface in volcanic emissions, over the aeons the store of water in the mantle has grown vast.
Some of this water forms hydrous minerals that essentially make the mantle more runny, says Condie, speeding up the flow of rock. The effect is strong enough to overcome the stiffening of the mantle caused by the gradual cooling inside Earth, he says.
Peter Cawood at the University of St Andrews in the UK thinks the work is interesting and provocative. "The overall increase in the rate of plate motion with time seems real and believable," he says, and could well be linked to changes in the mantle's water content – although convincing sceptics that plates move faster now will be difficult without more data, he adds.
That heat is ebbing away as Earth ages, and this was expected to slow plate motion.
originally posted by: CranialSponge
That heat is ebbing away as Earth ages, and this was expected to slow plate motion.
That should actually read as: Scientists are ASSUMING that the planet's heat is "ebbing away" as earth ages.... based on currently understood theoretical calculations.
They don't truly know whether it is or not.
Hell, for all they know, the core might actually be heating up. Which might even have the possibility to explain all kinds of things currently going on (ie: geomagnetic changes/depletion, suspected increased volcanic activity, suspected increased frequency of 5.0+ earthquakes, mysterious gaping holes and cracks opening up, a warming planet, changes to the jet stream/trade winds/hydrological cycle, mass animal dieoffs, etc etc).
A systemic domino effect per se...
Who knows ?
I love when you say "mass animal die-offs....."
originally posted by: midnightstar
well I for one think scientist are wrong saying the earths interior will cool .
mars being small this can happen but earth in much larger the heat earth is caused
by the pressure of the ground crust pushing downwards .so earth will never cool.
Ps this is my theory.
Geophysicists have established a mode of action that can explain the irregular distribution of
strong earthquakes at the San Andreas Fault in California. The scientists examined the electrical
conductivity of the rocks at great depths, which is closely related to the water content within the
rocks. From the pattern of electrical conductivity and seismic activity they were able to deduce
that rock water acts as a lubricant.
www.sciencedaily.com...
Deep burial means higher pressure and hotter temperatures, and very high temperature and
pressures cause the formation of new minerals, and mineral grains.
imnh.isu.edu...
For instance, the earth's core really does spin. If you cut the earth in half, it would look like a hard-boiled egg with a very large yolk. The shell represents the earth's 35-km (22 mile)- thick (or less) crust on which we walk and live. The egg white represents the 2,850- km (1770 mile)- thick mantle, the source of heat for Hawaiian and other hot spot volcanoes, and the yolk represents the 3,500-km (2172 mile) -thick core.
The core is made of two sections - a liquid outer core and a solid inner core. Both sections are made predominantly of iron and nickel. The inner core is under such great pressure that it cannot melt, even though temperatures are estimated at 3,700-6,000?C (6,700-10,800?F). This is about the temperature of the surface of the sun, while a sizzling molten lava flow from Kilauea is a cool 1,100?C (2,000?F).
hvo.wr.usgs.gov...
originally posted by: glend
a reply to: pikestaff
There is a theory called dynamo theory which might help explain the earths magnetic field. If the earths inner iron core attains it spin from interaction with suns magnetic field it might explain why earths magnetic field has become weaker at the same time as the suns. A slowing core might increase pressure (Bernoulli's principle) which could result in increase in volcanic activity.