The Earth has a (sadly inedible) jelly layer, scientists find

 

No wonder we have so many earthquakes: if you were standing on a jelly-filled donut, you'd be shaky too.

 

Anyone with an elementary school education is familiar with the Earth’s different layers—the inner and outer core, the mantle, and the crust. The lithosphere is comprised of the crust and the upper part of the mantle, and it’s broken up into tectonic plates. The movement of these plates is one of the causes of earthquakes. Beneath the lithosphere is the asthenosphere, another sub-layer of the mantle.

 

Science has now discovered the existence of another layer—one composed of “jelly-like” rock—which would explain how, exactly, the tectonic plates are able to move around.

 

Essentially, the Earth is like a giant jelly donut.

 

An explosive discovery

 

According to the current study, which was published in the journal Nature, there’s a 10 km-thick layer of “lubricating jelly-like rock” beneath the Pacific tectonic plate.

 

Researchers from New Zealand were able to generate seismic waves by detonating dynamite beneath the Earth’s surface. The blast zone was located at the tip of North Island in New Zealand, the area where the Pacific plate moves beneath the Australian plate. These resulting waves were around 500 m long and were able to resolve finer structures, compared to natural seismic waves generated by earthquakes, and their echoes revealed the existence of a jelly-like rock layer.

 

“Rather than relying on earthquake waves that come from below we create our own ‘earthquakes’ with dynamite shots,” said project lead Tim Stern, from Victoria University, Wellington.

 

The jelly layer is located between the lithosphere and asthenosphere, and allows the lithosphere to “float” along the surface of the asthenosphere.

 

“We always thought the boundary would be gradual and defined by temperature,” said geologist Andrew Gleadow, from the University of Melbourne. “This study shows it’s an abrupt transition and requires something more than temperature alone to explain it.”

 

The scientists proposed that the consistency of the jelly rock is caused by the magma or water concentration in the layer. The lithosphere is composed of around 0.1 percent magma, but the jelly layer may have a higher concentration. Even a 2 percent magma content would be enough to cause the difference in consistency.

 

A long-standing debate

 

This finding might be able to resolve a 50-year debate about whether or not plate tectonics are a result of pushing or pulling forces.

 

According to Gleadow, the jelly layer makes it less likely that either force is responsible and instead lends support to the theory that gravity is what causes plate movement.

 

“If the plates are mechanically disconnected from the mantle below, there can’t be good coupling to underlying convection movements.”

 

The next question, according to Louis Moresi, a geologist at the University of Melbourne, is whether or not this jelly layer exists worldwide. — TJD, GMA News