Archives de catégorie : only geology

New evidence suggests volcanoes caused biggest mass extinction ever

by University of Cincinnati, April 15, 2019 in ScienceDaily from Nature


Mercury found in ancient rock around the world supports theory that eruptions caused ‘Great Dying’ 252 million years ago.

Researchers say mercury buried in ancient rock provides the strongest evidence yet that volcanoes caused the biggest mass extinction in the history of the Earth.

The extinction 252 million years ago was so dramatic and widespread that scientists call it “the Great Dying.” The catastrophe killed off more than 95 percent of life on Earth over the course of hundreds of thousands of years.

Paleontologists with the University of Cincinnati and the China University of Geosciences said they found a spike in mercury in the geologic record at nearly a dozen sites around the world, which provides persuasive evidence that volcanic eruptions were to blame for this global cataclysm.

The study was published this month in the journal Nature Communications.

The eruptions ignited vast deposits of coal, releasing mercury vapor high into the atmosphere. Eventually, it rained down into the marine sediment around the planet, creating an elemental signature of a catastrophe that would herald the age of dinosaurs.

“Volcanic activities, including emissions of volcanic gases and combustion of organic matter, released abundant mercury to the surface of the Earth,” said lead author Jun Shen, an associate professor at the China University of Geosciences.

The Day the Dinosaurs Died

by Douglas Preston, April 8, 2019 in TheNewYorker


 

One of the central mysteries of paleontology is the so-called “three-­metre problem.” In a century and a half of assiduous searching, almost no dinosaur remains have been found in the layers three metres, or about nine feet, below the KT boundary, a depth representing many thousands of years. Consequently, numerous paleontologists have argued that the dinosaurs were on the way to extinction long before the asteroid struck, owing perhaps to the volcanic eruptions and climate change. Other scientists have countered that the three-metre problem merely reflects how hard it is to find fossils. Sooner or later, they’ve contended, a scientist will discover dinosaurs much closer to the moment of destruction.

Locked in the KT boundary are the answers to our questions about one of the most significant events in the history of life on the planet. If one looks at the Earth as a kind of living organism, as many biologists do, you could say that it was shot by a bullet and almost died. Deciphering what happened on the day of destruction is crucial not only to solving the three-­metre problem but also to explaining our own genesis as a species.

66-million-year-old deathbed linked to dinosaur-killing meteor

by U. of California – Berkeley, March 29, 2019 in ScienceDaily


Paleontologists have found a fossil site in North Dakota that contains animals and plants killed and buried within an hour of the meteor impact that killed the dinosaurs 66 million years ago. This is the richest K-T boundary site ever found, incorporating insects, fish, mammals, dinosaurs and plants living at the end of the Cretaceous, mixed with tektites and rock created and scattered by the impact. The find shows that dinosaurs survived until the impact.

Do volcanoes or an asteroid deserve blame for dinosaur extinction?

by Univ. of California – Berkeley, February 21, 2019 in ScienceDaily


Based on new data published today in the journal Science, it seems increasingly likely that an asteroid or comet impact 66 million years ago reignited massive volcanic eruptions in India, half a world away from the impact site in the Caribbean Sea.

But it leaves unclear to what degree the two catastrophes contributed to the near-simultaneous mass extinction that killed off the dinosaurs and many other forms of life.

The research sheds light on huge lava flows that have erupted periodically over Earth’s history, and how they have affected the atmosphere and altered the course of life on the planet.

Fake Science: “The Anthropocene Is Coming to Mars”… From Where?

by David Middleton, January 18, 2019 in WUWT


“The Anthropocene as a geological epoch is not formally recognized”… So… “The term Anthropocene has” NOT “been widely used for the current period in Earth’s geological history“.  It may be frequently used by activists and scientists who are ignorant of basic geology, but geologically speaking the term “Anthropocene” does not exist in any relationship to any period, epoch, age, era or eon in Earth’s geological history.

..

Yes, we have no Anthropocene, we have no Anthropocene today… Sung to the tune of Yes, We Have No Bananas.

Bacterial origin of the red pigmentation of Phanerozoic carbonate rocks: an integrated study of geology-biology-chemistry

by A. Préat et  al., December 2018 in GeologicaBelgica (with .pdf)


Abstract

Explaining the color of rocks is still a complex problem. This question was raised long ago in the community of geologists, particularly for the pigmentation of the ‘red marbles’ of the Frasnian of Belgium at the beginning of the last century, with many unsatisfactory hypotheses. Our recent analysis of different red carbonate rocks in Europe and North Africa (Morocco) may provide an alternative explanation for the color of these rocks. For this it was necessary to bring together diverse and complementary skills involving geologists, microbiologists and chemists. We present here a synthesis of these works. It is suggested that the red pigmentation of our studied Phanerozoic carbonate rocks, encompassing a time range from Pragian to Oxfordian, may be related to the activity of iron bacteria living in microaerophilic environments. A major conclusion is that this red color is only related to particular microenvironments and has no paleogeographic or climatic significance. All red carbonates have not necessarily acquired their pigmentation through the process established in this review. Each geological series must be analyzed in the light of a possible contribution of iron bacteria and Fungi.

Une question des plus simples en géologie : la couleur des roches ?

by Alain Préat, 21 décembre 2018 in ScienceClimatEnergie


pdf in ENGLISH

 

 Introduction

Cet article est le résultat d’une recherche multi-disciplinaire entre géologues et biologistes. Une synthèse de cette recherche vient d’être publiée en décembre 2018 sur le site de Geologica BelgicaUn article déjà publié dans SCE peut également être consulté.

Contrairement à ce que l’on peut penser, une question simple nécessite parfois des années de recherches avec des équipes diverses et des moyens sophistiqués. La question simple concerne ici la géologie et plus particulièrement la couleur des roches sédimentaires.

….

Fossils suggest flowers originated 50 million years earlier than thought

by eLife, December 18, 2018 in ScienceDaily


Scientists have described a fossil plant species that suggests flowers bloomed in the Early Jurassic, more than 174 million years ago, according to new research in the open-access journal eLife.

Before now, angiosperms (flowering plants) were thought to have a history of no more than 130 million years. The discovery of the novel flower species, which the study authors named Nanjinganthus dendrostyla, throws widely accepted theories of plant evolution into question, by suggesting that they existed around 50 million years earlier. Nanjinganthus also has a variety of ‘unexpected’ characteristics according to almost all of these theories.

Volcanoes fed by ‘mush’ reservoirs rather than molten magma chambers

by Imperial College London, December 4, 2018 in ScienceDaily


Volcanoes are not fed by molten magma formed in large chambers finds a new study, overturning classic ideas about volcanic eruptions.

Instead, the study suggests that volcanoes are fed by so-called ‘mush reservoirs’ — areas of mostly solid crystals with magma in the small spaces between the crystals.

Our understanding of volcanic processes, including those leading to the largest eruptions, has been based on magma being stored in liquid-filled ‘magma’ chambers — large, underground caves full of liquid magma. However, these have never been observed.

The new study, by researchers at Imperial College London and the University of Bristol and published today in Nature, suggests the fundamental assumption of a magma chamber needs a re-think.

Oxygen could have been available to life as early as 3.5 billion years ago

by Imperial College, November 27, 2018 in ScienceDaily


The levels of oxygen dramatically rose in the atmosphere around 2.4 billion years ago, but why it happened then has been debated. Some scientists think that 2.4 billion years ago is when organisms called cyanobacteria first evolved, which could perform oxygen-producing (oxygenic) photosynthesis.

Other scientist think that cyanobacteria evolved long before 2.4 billion years ago but something prevented oxygen from accumulating in the air.

Cyanobacteria perform a relatively sophisticated form of oxygenic photosynthesis — the same type of photosynthesis that all plants do today. It has therefore been suggested that simpler forms of oxygenic photosynthesis could have existed earlier, before cyanobacteria, leading to low levels of oxygen being available to life.

Now, a research team led by Imperial College London have found that oxygenic photosynthesis arose at least one billion years before cyanobacteria evolved. Their results, published in the journal Geobiology, show that oxygenic photosynthesis could have evolved very early in Earth’s 4.5-billion-year history.

See also here

Meeting Plate Tectonics – Peter Molnar

by D. Fernandez-Blanco, November 20, 2018 in EGU


What do you think are the biggest challenges right now in your field?

Some of the challenges are too hard for me even to pursue them. In the climate world, we don’t know about the role of clouds. And I don’t know how to pursue this, so I don’t pursue it. Do clouds have a cooling effect, and what is the response from clouds to warming? Will they slow or accelerate the warming? We don’t know. The role of clouds is certainly a big, big question. Although I do not work on this, I think about it, but I don’t see what to do.

One of the problems I do work on is what brought us Ice Ages. How did we go through 300 My years without much ice in the northern hemisphere and then suddenly, beginning 3My years ago or so, we had 5 big Ice Ages? Why? An easy answer is that now CO2 is higher. But it’s really hard to measure, determining CO2 in the past is a big question.

Another big question for me is how does the convection in the mantle connect with deformation in the lithosphere? How do these connect to one another?

Relics of ‘lost continents’ hidden under Antarctica are revealed by satellite images after scientists track 200 million years of tectonic plate shifts

by H. Pettit, November 9, 2018 in MailOnline


  • Images reveal a timeline of the ancient landmasses buried beneath Antarctica
  • They were taken by the long-dead Gravity field and Ocean Circulation Explorer 
  • The ESA satellite collected data on Earth’s gravitational pull

  • The study revealed that West Antarctica (green) has a thinner crust than East Antarctica (blue), which has a ‘family likeness to Australia and India’

USGS issues first USA Volcano Threat Assessment in over a decade

by Anthony Watts, October 24, 2018 in WUWT


18 volcanoes in the USA are classified as “very high threat”, many are in the Pacific Northwest.

Here the .pdf (USGS, 2018)

The United States has 161 young, active volcanoes within its borders. Since 1980, there have been 120 eruptions and 52 episodes of notable volcanic unrest at 44 U.S. volcanoes.

The U.S. Geological Survey systematically assesses U.S. volcanoes considered to be active or potentially active, and publishes a volcanic threat assessment that ranks the volcanoes based on 24 hazard and exposure factors. Last published in 2005, this 2018 update considers (1) field and laboratory research that adds or removes volcanoes from the list of potentially active volcanoes, and (2) updates the hazard and exposure factors used to produce a relative threat ranking of volcanoes.

Lessons from Dutch geological history might be useful for other present-day deltas

by Geological Society of America, October 9, 2018 in ScienceDaily 


Even long before medieval inhabitants reclaimed land and raised dykes at a large scale, humans have had a strong impact on river behavior in the Dutch delta plain. Physical geographers have demonstrated that two present Rhine branches developed stepwise in the first centuries CE, because of two combined man-induced effects.

Plate tectonics may have been active on Earth since the very beginning

by University of Tennessee at Knoxville, September 26, 2018 in ScienceDaily


A new study suggests that plate tectonics — a scientific theory that divides the earth into large chunks of crust that move slowly over hot viscous mantle rock — could have been active from the planet’s very beginning. The new findings defy previous beliefs that tectonic plates were developed over the course of billions of years.

The paper, published in Earth and Planetary Science Letters, has important implications in the fields of geochemistry and geophysics. For example, a better understanding of plate tectonics could help predict whether planets beyond our solar system could be hospitable to life.

“Plate tectonics set up the conditions for life,” said Nick Dygert, assistant professor of petrology and geochemistry in UT’s Department of Earth and Planetary Sciences and coauthor of the study. “The more we know about ancient plate tectonics, the better we can understand how Earth got to be the way it is now.”