Deep Sea Gods. Ancient marine organisms influence the strength of earthquakes
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Deposits of calcite left by masses of unicellular marine organisms millions of years ago control the movement and friction of lithospheric plates.
The attention of scientists is riveted to the Hikurangi subduction zone, which today is the largest fault in the vicinity of New Zealand. Scientists believe that this fault is capable of causing the largest earthquake of magnitude 8 or more, writes Science Alert.
A group of geologists from the University of Wellington Te Herenga Waka in New Zealand conducted their own study of this zone and came to conclusion that tiny marine organisms that lived on Earth millions of years ago can have a serious impact on subsequent seismic activity.
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Scientists have focused on studying calcite deposits formed by masses of unicellular marine organisms. The study shows that the level of movement and friction of the Pacific and Australian plates largely depends on this biomass.
According to structural geologist Carolyn Boulton, further seismic activity in the region depends on how masses of calcite dissolve. The fact is that calcite will dissolve faster under certain conditions – for example, low temperatures and stress. But high temperatures, on the contrary, slow down the dissolution – as a result, the masses of ancient deposits block the movement of the plate. Along with it, energy is also blocked, which later will be released anyway, but already during a large-scale surge.
Scientists studied the subduction zone and found that the temperature of the water here rises with depth – for every kilometer there is an increase in temperature by about 10º C. However, it was not so easy to explore the fault itself – expensive drilling equipment is required to access it. Therefore, scientists took a detour – they studied the open layers of limestone, mudstone and siltstone in the local coastline. The rocks in these regions also contain calcite from ancient marine organisms.
At the same time, the question of how much calcite is contained in the subduction zone and in what state it is now remains open. The main problem still remains the lack of knowledge of this region. However, the study of sediments in coastal regions is still able to shed light on future seismic activity.
Thus, scientists have concluded that in the next half century there is a 26% probability of a large-scale earthquake in the fault zone. The study shows that such seismic activity will cause a large tsunami – evidenced by the effects of previous earthquakes along the coast of New Zealand.