Dead creatures buried in the Pacific Ocean could play a role in the next devastating earthquake

Scientists have discovered an intriguing factor that could have influenced the magnitude of the devastating earthquake in the Hikuranga subduction zone, which is a metaphor for the fossils of tiny sea creatures that lived tens of millions of years ago.

The Hikuranga Induction Zone is the largest two-plate boundary fault in New Zealand and extends off the east coast of the North Island where the two plates meet. This is where the Pacific Plate is subducting under the Australian Plate according to the theory of plate tectonics. This region can generate strong earthquakes with the potential for destructive earthquakes greater than 8 on the Richter scale.

A new study shows that tiny ancient marine organisms can have a major impact on seismic events emanating from there.

Scientists studying the area have found that calcite deposits, left by accumulations of protozoan marine organisms tens of millions of years ago, can control the level of movement and friction between the Pacific Plate and the Australian Plate.

The scientists explain that if this calcite could dissolve, like a sugar cube in tea, in large enough quantities, it would allow two tectonic plates to slide easily without causing noticeable earthquakes on the surface. But if it doesn’t break apart, it will impede the movement of the plates, since the fault line can trap and store significant energy, which could eventually be released in the form of a more powerful earthquake.

“Calcite melts faster when stress is high and temperatures are lower,” says structural geologist Carolyn Bolton of the University of Te Herenga Waka, Victoria, Wellington, New Zealand. for example. “.but it is difficult to melt when the temperature rises, for example, in the bowels of the earth.”

In the interior of the subduction zone, the temperature gradually rises with depth, warming up by about 10 degrees Celsius for every kilometer of depth. Calcite shells that cannot melt deep below the surface can have a significant impact on fault movement.

The fault itself is difficult to reach because it requires expensive drilling equipment, so scientists have alternatively used exposed layers of limestone, mudstone and siltstone (or marl) on the local coast in the southeast of Martinborough, on North Island.

The rocks there contain calcite, a common carbonaceous mineral that comes from marine fossils, mostly of the type known as foraminifera (including plankton and other protozoan snails).

“The amount and behavior of the calcite formed by these organisms is a big part of the mystery about the strength of the next earthquake,” says Bolton.

Geologists know little about the Hikurangi Subduction Zone in New Zealand because it cannot be studied in depth. In addition, the record of previous earthquakes is not completely exhaustive, and information about its condition is inaccurate, making it difficult to predict the next major earthquake.

Scientists say there is a 26 percent chance that a major earthquake will occur along this fault in the next 50 years, which could trigger a major tsunami in ocean waters.

All sorts of factors come into play, but this study shows how slow and light plate movements can be, or how fast and large they can be, and the more we know about the accumulation of calcite underwater, the better, because we can understand what will happen next. .

“Just imagine how these long-dead microorganisms can affect the mechanical interaction of two huge tectonic plates,” says Bolton.

The results of this full study have been published in the journal Lithos.

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