Earth
Thu Jun 25, 2020 2:5
How Water in Deep Earth Triggers Earthquakes, Tsunamis
TEHRAN (FNA)- In a new study, published in the journal Nature, an international team of scientists provide the first conclusive evidence directly linking deep Earth's water cycle and its expressions with magmatic productivity and earthquake activity.

Water (H2O) and other volatiles (e.g. CO2 and sulphur) that are cycled through the deep Earth have played a key role in the evolution of our planet, including in the formation of continents, the onset of life, the concentration of mineral resources, and the distribution of volcanoes and earthquakes.

Subduction zones, where tectonic plates converge and one plate sinks beneath another, are the most important parts of the cycle -- with large volumes of water going in and coming out, mainly through volcanic eruptions. Yet, just how (and how much) water is transported via subduction, and its effect on natural hazards and the formation of natural resources, has historically been poorly understood.

Lead author of the study, Dr George Cooper, Honorary Research Fellow at the University of Bristol's School of Earth Sciences, said: "As plates journey from where they are first made at mid-ocean ridges to subduction zones, seawater enters the rocks through cracks, faults and by binding to minerals. Upon reaching a subduction zone, the sinking plate heats up and gets squeezed, resulting in the gradual release of some or all of its water. As water is released it lowers the melting point of the surrounding rocks and generates magma. This magma is buoyant and moves upwards, ultimately leading to eruptions in the overlying volcanic arc. These eruptions are potentially explosive because of the volatiles contained in the melt. The same process can trigger earthquakes and may affect key properties such as their magnitude and whether they trigger tsunamis or not."

Exactly where and how volatiles are released and how they modify the host rock remains an area of intense research.

Most studies have focused on subduction along the Pacific Ring of Fire. However, this research focused on the Atlantic plate, and more specifically, the Lesser Antilles volcanic arc, located at the eastern edge of the Caribbean Sea.

"This is one of only two zones that currently subduct plates formed by slow spreading. We expect this to be hydrated more pervasively and heterogeneously than the fast spreading Pacific plate, and for expressions of water release to be more pronounced," said Prof. Saskia Goes, Imperial College London.

The Volatile Recycling in the Lesser Antilles (VoiLA) project brings together a large multidisciplinary team of researchers including geophysicists, geochemists and geodynamicists from Durham University, Imperial College London, University of Southampton, University of Bristol, Liverpool University, Karlsruhe Institute of Technology, the University of Leeds, The Natural History Museum, The Institute de Physique du Globe in Paris, and the University of the West Indies.

"We collected data over two marine scientific cruises on the RRS James Cook, temporary deployments of seismic stations that recorded earthquakes beneath the islands, geological fieldwork, chemical and mineral analyses of rock samples, and numerical modelling," said Dr Cooper.

To trace the influence of water along the length of the subduction zone, the scientists studied boron compositions and isotopes of melt inclusions (tiny pockets of trapped magma within volcanic crystals). Boron fingerprints revealed that the water-rich mineral serpentine, contained in the sinking plate, is a dominant supplier of water to the central region of the Lesser Antilles arc.

"By studying these micron-scale measurements it is possible to better understand large-scale processes. Our combined geochemical and geophysical data provide the clearest indication to date that the structure and amount of water of the sinking plate are directly connected to the volcanic evolution of the arc and its associated hazards," said Prof. Colin Macpherson, Durham University

"The wettest parts of the downgoing plate are where there are major cracks (or fracture zones). By making a numerical model of the history of fracture zone subduction below the islands, we found a direct link to the locations of the highest rates of small earthquakes and low shear wave velocities (which indicate fluids) in the subsurface," said Prof. Saskia Goes.

The history of subduction of water-rich fracture zones can also explain why the central islands of the arc are the largest and why, over geologic history, they have produced the most magma.

"Our study provides conclusive evidence that directly links the water-in and water-out parts of the cycle and its expressions in terms of magmatic productivity and earthquake activity. This may encourage studies at other subduction zones to find such water-bearing fault structures on the subducting plate to help understand patterns in volcanic and earthquake hazards," said Dr Cooper.

"In this research we found that variations in water correlate with the distribution of smaller earthquakes, but we would really like to know how this pattern of water release may affect the potential -- and act as a warning system -- for larger earthquakes and possible tsunami," said Prof. Colin Macpherson.

 

 

 

 

Bottom top
Iran to Fight Coronavirus More Seriously via Increase of Medical, Health Items Production

TEHRAN (FNA)- An official with the Industry Ministry said that Iran has succeeded in multiplying production of various items and equipment to help the nationwide battle against COVID-19.
Labour: Unemployment in UK Could Go 'Way Beyond Anything We've Experienced'

TEHRAN (FNA)- Unemployment could soar to levels “way beyond anything we’ve experienced before” unless the government extends the furlough scheme and gets to grips with the looming crisis, Labour announced.
White House Reportedly Plans to Interview Pentagon Officials for 'Political Litmus Test'

TEHRAN (FNA)- The American magazine Foreign Policy quoted unnamed sources as saying that as of next week, White House staffers will start interviewing political appointees at the US Department of Defense.
Washington State Claims US Gov't Providing Unsterile COVID-19 Screening Supplies Amid Surge in Testing Demand

TEHRAN (FNA)- Medical supplies sent by the federal government to help with coronavirus testing have been too slow to arrive and have failed quality control checks, according to Washington state’s top health official.
Official: 20% of Iranians Infected with Coronavirus

TEHRAN (FNA)- A senior Iranian medical official said that nearly 18mln people in Iran have so far been infected with the COVID-19 virus.
Top Security Official: US Assassination of General Soleimani Huge Gift to Terrorists

TEHRAN (FNA)- Secretary of Iran's Supreme National Security Council (SNSC) Ali Shamkhani said that Washington's assassination of former IRGC Quds Force Commander Lieutenant General Qassem Soleimani was the biggest gift to the terrorists in the region.
Iran No More Needs Foreign Aid to Repair Offshore Drilling Rigs

TEHRAN (FNA)- An official of Mostazafan Foundation announced that Iran has become self-sufficient in repairing offshore drilling rigs.
Iran Identifies 2,449 New Coronavirus Cases

TEHRAN (FNA)- The Iranian health ministry announced on Saturday that 2,449 new cases of infection to COVID-19 virus have been diagnosed in the country in the past 24 hours, adding that 1,148 patients have been hospitalized.
Tehran, Moscow Confer on Energy Cooperation, Upcoming Joint Commission

TEHRAN (FNA)- Iranian envoy to Moscow Kazzem Jalali met with Russian Deputy Energy Minister Anatoly Tikhonov and held talks on the upcoming mutual energy cooperation within the framework of the joint economic commission.
Over 1 Ton of Narcotics, Four Smugglers Captured in Southern Iran

TEHRAN (FNA)- Anti-narcotics police seized 1,087 kilograms of illicit drugs and disbanded four trafficking gangs in South of Iran, a judiciary official of Hormozgan province announced on Saturday.
More Coronavirus Restrictions in Place in Iran as of July 5

TEHRAN (FNA)- Iranian President Hassan Rouhani said on Saturday that wearing mask will be compulsory in crowded and public places as of Sunday (July 5).
Iran’s FM Wishing Instant Recovery for Pakistani Counterpart

TEHRAN (FNA)- Iranian Foreign Minister Mohammad Javad Zarif expressed hope that Pakistan’s Foreign Minister Shah Mahmoud Qureshi who has tested positive for coronavirus will recover immediately.
UK Chancellor Urges Public to Head Back to Pubs, Restaurants to Help Save Economy

TEHRAN (FNA)- Chancellor Rishi Sunak urged Britain to “eat out to help out” in a bid to boost the economy as it emerges from a lockdown slump.
US Troops Ordered to Suspend Activities in Colombia After Presence Deemed Unlawful

TEHRAN (FNA)- US troops have been ordered to suspend activities in Colombia for 48 hours after a court ruled that their presence in the South American country was unlawful.
COVID-19 in Spain: Local Lockdown in Catalonia Due to Virus Outbreak

TEHRAN (FNA)- The government of Catalonia announced on Saturday that the county of Segria will be placed under lockdown to try to contain the spread of COVID-19.