Archives par mot-clé : Geology

Volcanic activity, declining ocean oxygen triggered mass extinction of ancient organisms

by Florida State University, June 11, 2018 in ScienceDaily


Global climate change, fueled by skyrocketing levels of atmospheric carbon dioxide, is siphoning oxygen from today’s oceans at an alarming pace — so fast that scientists aren’t entirely sure how the planet will respond.

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Millions of years ago, scientists discovered, powerful volcanoes pumped Earth’s atmosphere full of carbon dioxide, draining the oceans of oxygen and driving a mass extinction of marine organisms.

Le Précambrien de l’Afrique de l’Ouest : que d’événements globaux riches d’enseignements

by Alain Préat, 31 mai 2018, Académie Royale des Sciences d’Outre- Mer


Le Précambrien représente 88% de l’histoire de la Terre âgée de 4,567 milliards d’années (Ga).

C’est au cours de cette période peu connue, peu enseignée que se sont déroulés ou mis en place des événements physico-chimiques et biologiques déterminants: différenciation des enveloppes terrestres, tectonique des plaques et premières ‘pangées’ ou supercontinents, champ magnétique, chaînes de montagnes, glaciations, anoxies des bassins, remplacement du CO2-CH4par l’oxygène atmosphérique, formation de gisements (uranium, manganèse, nickel …. et même pétrole), émergence dès 3,8 Ga des procaryotes puis des eucaryotes …

Vu l’absence de fossiles stratigraphiques, et donc de biozones, la stratigraphie du Précambrien est encore très difficile, elle  est intialement basée sur la lithostratigraphie. De grands progrès ont récemment été réalisés grâce à la chimiostratigraphie istotopique (C, O, Sr….) en plus de la radiométrie absolue.

L’exposé se consacrera aux événements sédimentaires liés au Grand Evénement de l’Oxygène il y a environ 2,5-2,1 Ga (Paléoprotérozoïque) et à ceux liés à la ‘Terre Boule de Neige’ (Snowball Earth) avec la glaciation marinoenne il y a 0,635 Ga (Néoprotérozoïque), à partir des séries de l’Afrique de l’Ouest.

 

When the dinosaurs died, so did forests — and tree-dwelling birds

By Field Museum, May 24, 2018 in ScienceDaily (CurrentBiology)


Sixty-six million years ago, the world burned. An asteroid crashed to Earth with a force one million times larger than the largest atomic bomb, causing the extinction of the dinosaurs. But dinosaurs weren’t the only ones that got hit hard — in a new study, scientists learned that the planet’s forests were decimated, leading to the extinction of tree-dwelling birds.

Remember when were told sea creatures couldn’t run from global warming? Never mind.

by Anthony Watts, may 17, 2018 in WUWT


By investigating fossils, Prof. Kießling and Dr. Carl Reddin, who is also at GeoZentrum Nordbayern, have shown that coral, molluscs, and sponges have been following their preferred cold and warm zones for half a billion years. Isotherms (geographic lines denoting the same temperature, for example 20°C) shift towards the poles or the equator as soon as the global temperature rises or decreases. Isotherms have been shifting towards the poles for several years due to global warming.

The tendency towards climate-related migration is most apparent in tropical species. This may be due to the fact that several of these species live near the thermal maximum for complex organisms of 35-45°C . Current global warming trends are driving marine animals towards the poles, provided there is a suitable habitat they can migrate to.

Earth’s orbital changes have influenced climate, life forms for at least 215 million years

by Columbia University, May 7, 2018 inPhysOrg


Scientists drilling deep into ancient rocks in the Arizona desert say they have documented a gradual shift in Earth’s orbit that repeats regularly every 405,000 years, playing a role in natural climate swings. Astrophysicists have long hypothesized that the cycle exists based on calculations of celestial mechanics, but the authors of the new research have found the first verifiable physical evidence. They showed that the cycle has been stable for hundreds of millions of years, from before the rise of dinosaurs, and is still active today. The research may have implications not only for climate studies, but our understanding of the evolution of life on Earth, and the evolution of the Solar System. It appears this week in the Proceedings of the National Academy of Sciences.

Read more here

Tiny fossils unlock clues to Earth’s climate half a billion years ago

by University of Leicester, May 9, 2018 in ScienceDaily


The research, published in Science Advances, suggests that early animals diversified within a climate similar to that in which the dinosaurs lived.

This interval in time is known for the ‘Cambrian explosion’, the time during which representatives of most of the major animal groups first appear in the fossil record. These include the first animals to produce shells, and it is these shelly fossils that the scientists used.

Data from the tiny fossil shells, and data from new climate model runs, show that high latitude (~65 °S) sea temperatures were in excess of 20 °C. This seems very hot, but it is similar to more recent, better understood, greenhouse climates like that of the Late Cretaceous Period.

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West Antarctic Volcano and Fault Belt Part of ‘Pacific Ring of Fire’

by J.E. Kamis, May 7, 2018 in ClimateChangeDispatch


The inclusion of the here-termed West Antarctic Volcano and Fault Belt into the Pacific Ring of Fire will raise scientific awareness concerning the idea, as per the Plate Climatology Theory, that geologically induced heat flow is the root cause of many anomalous changes in Antarctica’s ecosystems, oceans, climate, and ice masses.

Did the transition to plate tectonics cause Neoproterozoic Snowball Earth?

by R.J. Stern and N.M. Miller, December 20, 2017 in TerraNova


When Earth’s tectonic style transitioned from stagnant lid (single plate) to the modern episode of plate tectonics is important but unresolved, and all lines of evidence should be considered, including the climate record. The transition should have disturbed the oceans and atmosphere by redistributing continents, increasing explosive arc volcanism, stimulating mantle plumes and disrupting climate equilibrium established by the previous balance of silicate‐weathering greenhouse gas feedbacks. Formation of subduction zones would redistribute mass sufficiently to cause true polar wander if the subducted slabs were added in the upper mantle at intermediate to high latitudes. The Neoproterozoic Snowball Earth climate crisis may reflect this transition. The transition to plate tectonics is compatible with nearly all proposed geodynamic and oceanographic triggers for Neoproterozoic Snowball Earth events, and could also have contributed to biological triggers. Only extraterrestrial triggers cannot be reconciled with the hypothesis that the Neoproterozoic climate crisis was caused by a prolonged (200–250 m.y.) transition to plate tectonics.

How Oman’s Rocks Could Help Save the Planet

by Henri Fountain, April 26, 2018 in TheNewYorkTimes


IBRA, Oman — In the arid vastness of this corner of the Arabian Peninsula, out where goats and the occasional camel roam, rocks form the backdrop practically every way you look.

But the stark outcrops and craggy ridges are more than just scenery. Some of these rocks are hard at work, naturally reacting with carbon dioxide from the atmosphere and turning it into stone.

Veins of white carbonate minerals run through slabs of dark rock like fat marbling a steak. Carbonate surrounds pebbles and cobbles, turning ordinary gravel into natural mosaics.

Even pooled spring water that has bubbled up through the rocks reacts with CO2 to produce an ice-like crust of carbonate that, if broken, re-forms within days.

Scientists say that if this natural process, called carbon mineralization, could be harnessed, accelerated and applied inexpensively on a huge scale — admittedly some very big “ifs” — it could help fight climate change. Rocks could remove some of the billions of tons of heat-trapping carbon dioxide that humans have pumped into the air since the beginning of the Industrial Age.

And by turning that CO2 into stone (…)

Clear as mud: Desiccation cracks help reveal the shape of water on Mars

by Geological Society of America and in Geology, April 19,2018 in ScienceDaily


.pdf of the article

In early 2017 scientists announced the discovery of possible desiccation cracks in Gale Crater, which was filled by lakes 3.5 billion years ago. Now, a new study has confirmed that these features are indeed desiccation cracks, and reveals fresh details about Mars’ ancient climate.

“We are now confident that these are mudcracks,” explains lead author Nathaniel Stein, a geologist at the California Institute of Technology in Pasadena. Since desiccation mudcracks form only where wet sediment is exposed to air, their position closer to the center of the ancient lake bed rather than the edge also suggests that lake levels rose and fell dramatically over time.

10 new islands formed in the last 20 years

by Sidney Stevens, July 5, 2016 in mother.nature.network


Yes, islands are disappearing — most recently the five Solomon Islands lost to rising sea levels. But don’t despair just yet. For every island that goes the way of the dodo bird, the Earth is busy creating new islands.

Some erupt into being through volcanic activity. Others grow from ocean sandbars. Still others reveal themselves after glaciers retreat. A few are only temporary, while some materialize and erode on a regular basis. However they’re birthed and however long they last, island-building is part of the amazing mystery of our living, breathing planet.

Here are 10 of Mother Nature’s newest islands formed in the past two decades (and one still in the embryonic stage).

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Mountain erosion may add CO2 to the atmosphere

by Woods Hole Oceanographic Institution, April 12, 2018 in ScienceDaily


Scientists have long known that steep mountain ranges can draw carbon dioxide (CO2) out of the atmosphere — as erosion exposes new rock, it also starts a chemical reaction between minerals on hill slopes and CO2 in the air, ‘weathering’ the rock and using CO2 to produce carbonate minerals like calcite.

Experimental Constraints on Forecasting the Location of Volcanic Eruptions from Pre-eruptive Surface Deformation

by F. Guldstrand et al., 2018 in Front.Earth.Sci.


Key Points

• We quantitatively analyse pre-eruptive intrusion-induced surface deformation from 33 scaled laboratory experiments resulting in eruptions.

• A robust proxy extracted from surface deformation geometry enables systematic predictions of the locations of a subsurface intrusion and imminent eruption.

• Forecasting an eruption location is possible without geodetic modeling but requires volcano monitoring at high spatiotemporal resolution.

Unique diamond impurities indicate water deep in Earth’s mantle

by University of Nevada, March 9, 2018 in ScienceDaily


A UNLV scientist has discovered the first direct evidence that fluid water pockets may exist as far as 500 miles deep into the Earth’s mantle.

Groundbreaking research by UNLV geoscientist Oliver Tschauner and colleagues found diamonds pushed up from the Earth’s interior had traces of unique crystallized water called Ice-VII.

See alos here