Volcanic Plumes: Crafters of Continents or Ghosts in the Earth?
Hi-Resolution simulations show that plumes of magma rising from miles below ground could be responsible for the breakup of continents under special circumstances.
Volcanoes are as endlessly fascinating as they are potent forces of nature. Not only can they flood the land with lava and infuse the atmosphere with their gasses; whatever it is that causes them may also be responsible for the breakup of continents.
The textbooks say it all starts with the plumes. It is believed that thin columns of melted rock rise from the boundary of the earth’s outer core and lower mantle and travel hundred of kilometers until they mushroom against the lid of the world below our feet. To balance this upwelling, wide chunks of cooling mantle would then descend. What these magma columns or mantle plumes do next to the surface of the earth is what is described in a recent study published in the Journal Nature.
To answer this question, researchers created the highest resolution 3D model ever created showing the interaction of mantle plumes with earth’s surface. The results show that plumes, as massive and powerful as they are, are still generally too weak to pierce the middle of a tectonic plate….except in certain situations. The researchers liken these plates to Saran wrap that is difficult to breach unless its taut. Casual, unstressed tectonic plates then would only form a distinctive hump in the ground if a plume tried to break through. If that plate however was experiencing some form of tensile stress (if it were locked tightly to another plate or overlapping one) then it could potentially break through and create crevices or even thousand mile long rift valleys potentially leading to the complete breakup of a plate into smaller ones.
It’s quite hard though to confidently implicate mantle plumes since geologic processes can take millions of years to reveal their handy-work. This makes agreement among geologists at times difficult since other theories could also account for what is observed on the surface. In fact, there is quite a controversy going on right now whether mantle plumes even exist or not.
This has been brought to a head recently due to seismic studies which appear to show that thin jets or mantle plumes rising from halfway down to the core do not exist. Instead, researchers claim that the most likely scenario now is the opposite of a mantle plume. They contend that broad 1,000 km wide chunks of mantle slowly rise in response to cooling columns of material called slabs sinking into the depths. This whole process then is initiated by the cooling and sinking slabs and not anything happening kilometers below the surface.
So in this corner we have a hi resolution 3D simulation. In the other corner we have Seismic observations that appear to rewrite the textbooks. Both theories can explain volcanism but each are quite different.
I’m gonna let the geologists duke this one out but all else being equal, I tend to favor solid observation over virtual simulation.
Image Credit: From Mitch Battros Earth Changes Media website