Tag Archives: continents

Research: Collaboration between oceans and continents led to Mesozoic marine extinctions

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in paper Published in the journal Nature ChemistryScientists have proposed a new explanation for a series of severe environmental crises known as marine anoxia, which occurred between 185 and 85 million years ago (during the Mesozoic era) when the amount of dissolved oxygen in the oceans became extremely low.

Oceanic anoxia was a geologically abrupt phase of extreme oxygen depletion in the oceans that disrupted marine ecosystems and led to evolutionary shifts. These events, which usually lasted about 1.5 million years, occurred frequently during the Mesozoic Era, between about 183 and 85 million years ago. One hypothesis suggests that anoxia resulted from increased chemical weathering of the Earth's surface on a greenhouse world with high volcanic carbon emissions. Gernon othersA combination of plate reconstructions, tectonic geochemical analyses and global biogeochemical modelling tested this hypothesis. Image courtesy of the University of Southampton.

“Ocean anoxia is like hitting the reset button on the Earth's ecosystems,” said Prof Tom Gernon, from the University of Southampton.

“The challenge was to understand what geological forces pushed the button.”

The researchers investigated the influence of plate tectonic forces on ocean chemistry during the Jurassic and Cretaceous periods, collectively known as the Mesozoic Era.

“This period in Earth's history is also known as the Age of the Dinosaurs and is well exposed along the cliffs of the Jurassic Coast on the south coast of England, Whitby in Yorkshire and Eastbourne in East Sussex,” Prof Gernon said.

Scientists have combined statistical analysis and advanced computer modelling to investigate how the ocean's chemical cycle may have responded to the breakup of the supercontinent Gondwana, the giant landmass once home to dinosaurs.

“During the Mesozoic Era, the continents broke apart and intense volcanic activity occurred around the world,” Prof Gernon said.

“As the plates shifted and new ocean floor was formed, phosphorus, a nutrient essential to life, was released in large quantities into the ocean from weathered volcanic rocks.”

“Importantly, we found evidence of multiple instances of chemical weathering on both the ocean floor and the continents, alternating between destroying the oceans — like a geological tag team.”

The authors find that the timing of these weathering waves coincides with most of the marine anoxic events in the rock record.

They argue that phosphorus that entered the ocean through weathering acted as a natural fertilizer, promoting the growth of marine life.

However, this fertilization phenomenon came at a great cost to marine ecosystems.

“Increased biological activity caused huge amounts of organic matter to sink to the seafloor, consuming huge amounts of oxygen,” said Prof Benjamin Mills, from the University of Leeds.

“This process ultimately left large swaths of the ocean anoxic, or 'dead zones' where oxygen was depleted and most marine life died.”

“The anoxic conditions typically lasted for one to two million years and had profound effects on marine ecosystems, the effects of which are still felt today.”

“The organic-rich rocks that accumulated during these events are the source of the world's largest commercial oil and gas reserves to date.”

The findings explain the causes of extreme biological chaos during the Mesozoic Era and highlight the devastating effects of nutrient overload on marine environments today.

“Studying geological events provides valuable insights that help us understand how Earth will respond to future climatic and environmental stresses,” Professor Gernon said.

Overall, the results reveal stronger-than-expected connections between Earth's solid interior and its surface environment and biosphere, especially during periods of tectonic and climatic upheaval.

“It is remarkable how a series of events occurring inside the Earth can have such profound, often devastating, effects on the surface,” Prof Gernon said.

“Continental breakup could have profound effects on evolutionary processes.”

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TM Gernon othersSolid Earth forcing of Mesozoic oceanic anoxia. National GeographyPublished online August 29, 2024, doi: 10.1038/s41561-024-01496-0

This article has been adapted from an original release from the University of Southampton.

Source: www.sci.news

Fresh study challenges commonly accepted ideas of how continents are formed

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In the new study, Dr David Hernández Uribe from the University of Illinois at Chicago used computer models to study the formation of magma, which is thought to hold clues to the origin of Earth's continents.

Hadean Earth. Image by Alec Brenner.

Magma is molten material that forms rocks and minerals as it cools.

Dr Hernández Uribe searched for magma that matched the compositional characteristics of rare mineral deposits called zircons, which date back to the Archean Era (2.5 to 4 billion years ago), when scientists believe the continents first formed.

In a recent study, researchers argued that Archean zircons could only have been formed by subduction, i.e. two crustal plates colliding under the ocean and pushing land up onto the surface.

This process still occurs today, causing earthquakes and volcanic eruptions and reshaping the coastlines of continents.

However, Dr. Hernández Uribe found that subduction was not necessary for the formation of Archean zircons.

Rather, he found that the minerals may have formed due to the high pressures and temperatures associated with the melting of Earth's thick primordial crust.

“Using my calculations and models, we can get the same characteristics in zircons and even a better match through partial melting at the base of the crust,” Dr Hernández Uribe said.

“So based on these results, we don't yet have enough evidence to say by what process the continents formed.”

The findings also create uncertainty about when plate tectonics began on Earth.

If Earth's first continents formed by subduction, then the continents would have started moving between 3.6 and 4 billion years ago, or just 500 million years after Earth existed.

But an alternative theory, that the first continents formed from melting crust, means that subduction and tectonic shifts may have started much later.

“As far as we know, Earth is the only planet in the solar system where plate tectonics is actively occurring,” Dr Hernández Uribe said.

“And this has implications for the origin of life, because how the first continents moved controlled the weather, controlled the chemistry of the oceans, and controlled everything related to life.”

of study Published in the journal on July 11, 2024 Nature Chemistry.

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Hernández-Uribe, D. Generation of Archean oxidized and wet magmas by mafic crustal overthickening. National GeographyPublished online July 11, 2024; doi: 10.1038/s41561-024-01489-z

This article is a version of a press release from the University of Illinois at Chicago.

Source: www.sci.news

Report states Europe is experiencing the greatest rate of warming among all continents

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Europe is the continent experiencing the most rapid increase in temperature, with its temperatures rising at approximately twice the global average, as reported by two top climate watchdogs on Monday. This raises concerns about human health, glacier melting, and the impact on economic activity.

The World Meteorological Organization of the United Nations and the European Union’s climate change agency Copernicus jointly reported that the African continent has the potential to transition to renewable resources like wind, solar, and hydropower in response to the effects of climate change. There is an opportunity to develop specific strategies to accelerate action on climate change.

Last year, the European Climate Report stated that the continent generated 43% of its electricity from renewable sources, up from 36% the previous year. In Europe, more energy was produced from renewables than fossil fuels for the second consecutive year.

According to the report, the latest five-year average temperature shows Europe to be currently 2.3 degrees Celsius (4.1 degrees Fahrenheit) above pre-industrial levels, compared to the global temperature being 1.3 degrees Celsius warmer. This is just below the target set in the 2015 Paris climate agreement to limit global warming to 1.5 degrees Celsius.

Firefighters and volunteers extinguish a burning field during a forest fire in Salonida, Greece, July 17, 2023.
Nick Paleologos/Bloomberg from Getty Images File

“Europe has continued to face rising temperatures and extreme weather events this year, including heat stress from record temperatures, wildfires, heatwaves, glacier ice loss, and inadequate snowfall,” said Elisabeth Hamdoush, Deputy Division Chief of the EU Executive Director Copernicus.

This report complements the World Meteorological Organization’s flagship State of the World Climate Report, which has been published annually for 30 years and this year issued a “Red Alert” warning that the world is not taking sufficient action to combat the effects of global warming.

In March, Copernicus reported achieving a record for 10 consecutive months of record-breaking temperatures. According to a European report, the average sea surface temperature across oceans in Europe is expected to reach its highest annual level in 2023.

This year’s European report focuses on the impact of high temperatures on human health, noting a rise in heat-related deaths across the continent. Over 150 lives were directly lost due to storms, floods, and wildfires last year.

Economic losses related to weather and climate in 2023 are estimated to exceed 13.4 billion euros (around $14.3 billion).

Carlo Buontempo, Director of Copernicus, stated, “In 2023, hundreds of thousands of people will be affected by extreme weather events causing significant damage at a continental level, with an estimated cost of at least tens of billions of euros.” “It’s been done,” he said.

The report highlights that extreme weather conditions have led to heatwaves, wildfires, droughts, and floods. High temperatures are causing the reduction of glaciers on continents, including the Alps, where about 10% of glaciers have been lost over the past two years. Glacier ice has been declining.

Nevertheless, the authors of the report pointed out some exceptions, such as Scandinavia and Iceland, where temperatures were below average despite above-average mercury concentrations across much of the continent.

Source: www.nbcnews.com