Rocks from two hundred million years ago show us how everything died and how nothing is new.
- A new study suggests that the mass extinction that gave dinosaurs the evolutionary upper hand was caused by oceanic oxygen deprivation.
- Using ratios of sulfur isotopes, researchers could estimate changes in ocean oxygen levels in ancient seas.
- The authors suggest a similar mechanism as that which can cause dead zones in oceans today caused a mass extinction.
How to tell what the world was like 201 million years ago using rocks<p>The mass extinction that ended the Triassic period was a massive die-off that saw somewhere between a quarter and a third of ocean life vanish alongside most large land <a href="https://en.wikipedia.org/wiki/Triassic%E2%80%93Jurassic_extinction_event" target="_blank">animals</a>. Plants were not spared a culling either, with perhaps 60 percent of plant species also dying. The event took less than 10,000 years to carry out this morbid work. This remarkable event paved the way for dinosaurs to become the dominant land animal during the Jurassic period, as most of their competition was dead.</p><p>Explanations for this event's cause have ranged from gradual climate change, to asteroid impacts, to rampant volcanism. New evidence suggests that <a href="https://en.wikipedia.org/wiki/Anoxic_event" target="_blank">ocean anoxia</a>, the depletion of oxygen supplies in the ocean, played a large role. </p><p>The researchers examined the levels of two isotopes of sulfur in rocks that would have been on the seafloor during the extinction event from British Columbia, Sicily, and Northern Ireland. The two isotopes, <sup>32</sup>S and <sup>34</sup>S, can become trapped in limestone and other rocks and exist at different ratios depending on how much oxygen is in the water around them. By examining the changes in the ratio of the two isotopes in rocks formed at the time, we can know what was happening to oxygen levels in the oceans hundreds of millions of years ago. </p><p>The scientists noticed "large spikes" in the ratio of <sup>34</sup>S to <sup>32</sup>S in the samples from all of the locations, indicative of a substantial fall in the amount of oxygen available. These findings can be applied far beyond the sites the rock samples came from, suggesting that oxygen levels fell across large portions of the globe-spanning superocean, known as <a href="https://en.wikipedia.org/wiki/Panthalassa" target="_blank" rel="noopener noreferrer">Panthalassa, </a>that existed alongside Pangea.<strong> </strong></p>
And you thought the Dead Zone in the Gulf of Mexico was bad.<iframe width="730" height="430" src="https://www.youtube.com/embed/yObCpYLLJSk" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe><p>This study isn't the only one suggesting Ocean anoxia caused the extinction event. A previous <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GC006941" target="_blank">study</a> from 2017 reached a similar conclusion by measuring the trace uranium levels in rocks formed at the time. Similarly to the ratio of sulfur isotopes considered above, the amount of uranium in these rocks varies with the amount of oxygen. That study suggests that the low oxygen levels may have lasted 50,000 years after their initial fall, with a full 250,000 years needed before coral reefs could <a href="https://phys.org/news/2017-08-global-oceanic-dead-zones-persisted.html" target="_blank">recover</a>.</p><p>In the present day, the researchers hypothesize that this anoxia was connected to significant volcanic activity at the time. By releasing massive amounts of greenhouse gasses, this would have both acidified the oceans by increasing their carbon content and lowered their oxygen levels by raising global temperatures, as warm water holds less oxygen <a href="http://limnoloan.org/waterquality/dissolved_oxygen/#:~:text=Warm%20water%20holds%20less%20dissolved,to%20escape%20from%20the%20water.&text=Therefore%20the%20warmer%20and%20saltier,dissolved%20oxygen%20it%20will%20contain." target="_blank">overall</a>. Together, these effects can annihilate marine <a href="https://en.wikipedia.org/wiki/Ocean_acidification#Ecosystem_impacts_amplified_by_ocean_warming_and_deoxygenation" target="_blank" rel="noopener noreferrer">ecosystems</a>. It is known that major volcanic activity was occurring at the time, lending credence to this <a href="https://en.wikipedia.org/wiki/Central_Atlantic_magmatic_province" target="_blank" rel="noopener noreferrer">hypothesis</a>. </p><p>It's a good thing that nothing is causing the oceans to heat up and have lower oxygen levels these days! Oh, <a href="https://en.unesco.org/sites/default/files/iucndeoxreportbook15-11-2019.pdf" target="_blank" rel="noopener noreferrer">wait</a>. Never mind. </p>
Two Williams pioneered geological mapping in Britain and the United States - but the world only remembers one.
Weirdly beautiful maps<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzgwMDM3MC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYzODg2NTgyNX0.MNuSQ4dKy2TUIi_MhtddiGwc9VZTQfDD27AlOzYrs14/img.png?width=980" id="64be9" class="rm-shortcode" data-rm-shortcode-id="d9e99862d6090a76cf013eb2829d810b" data-rm-shortcode-name="rebelmouse-image" alt="Strata Smith: The Man & The Map" />
William 'Strata' Smith with some of his fossils and part of his map: still from a short video by the British Geological Survey.
Credit: YouTube<p>Here's one of the worst raps science gets: it has disenchanted the world. Literally <em>dis-enchanted </em>it, by replacing magic with measurement. And so, it has reduced the miracle of life to the banality of being.</p><p>There is plenty wrong with that assessment, but nowhere is it more untrue than in the field of geology. Earth scientists have given eloquent voices to the dumb mud and mute rocks beneath our feet. They've pieced together the deep history of the subterranean world – more ancient and more violent than anyone imagined. And they've produced weirdly beautiful maps like these.</p><p>Weird, because those colors and borders resist all identification with subdivisions we're more familiar with, like political entities, climate zones or land-use types. No, geological maps strip away all those fads and deal only with the non-ephemeral: the origin and nature of the land itself. <br></p>
The map that changed the world<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzgwMDM5My9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYzMDcxOTIwMX0.FpRMtskdxZ0GxMPqow69--f3c3T-WTVzS3QVs-qFLgA/img.png?width=980" id="f1162" class="rm-shortcode" data-rm-shortcode-id="1829b44147fbf6e537767581fb556540" data-rm-shortcode-name="rebelmouse-image" alt="'A Delineation of the Strata of England and Wales, with Part of Scotland; Exhibiting the Collieries and Mines, the Marshes and Fen Lands Originally Overflowed by the Sea, and the Varieties of Soil According to the Variations in the Substrata, Illustrated by the Most Descriptive Names'." />
Smith single-handedly mapped an area of more than 175,000 km2 (67,500 sq. mi). Eventually only about 400 copies of the completed map were issued in 1815. About 40 survive today.
Image: Natural History Museum<p>Arguably the most famous map in the history of geology is this one, published in 1815 by William Smith, showing the stratification of England, Wales and part of Scotland. For the first time ever, this map presented a detailed overview of the geology of an entire country. </p><p><span></span>It set the standard for all geology maps that have followed. And it turned geology into a 'practical' science – helping industrialists locate mineable coal seams, for example. Indeed, this was "The Map that Changed the World," as described in a bestselling book of that title.</p><p>The book, by Simon Winchester, focuses on the mapmaker's compelling life story. Nicknamed 'Strata' Smith, the lowly-born surveyor noticed how fossils occurred in predictable layers in the side of a freshly dug canal. He struck upon the idea of a stratified geological past and spent the first decade and a half of the 19th century surveying most of Britain to prove his theory. <br></p>
Ostracism and plagiarism<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzgwMDM3NC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY1NTUwNjY1NH0.4vjgHJo2v-TYWBv6OEVfJ7Fqc-26Fyp5x_KjDHBuEPs/img.png?width=980" id="1eed6" class="rm-shortcode" data-rm-shortcode-id="0477bd73285f71f8af2174f8a09a21d6" data-rm-shortcode-name="rebelmouse-image" alt="William Smith\u2019s Geological section from London to Snowdon, showing the varieties of the strata, and the correct altitude of the hills." />
Accompanying Smith's map was a cross-section of the country, from Snowdon (left) to London, showing how the strata in southern England dip towards the southeast. This was effectively the first 'block diagram', now a standard feature of geographical cartography.
Credit: Natural History Museum<p>Smith's map is remarkably similar to current geological maps of Britain, proving the accuracy of his work. But he had some trouble convincing his contemporaries – which was due at least in part to class differences: London's Geological Society was a gentleman's club, not the natural <em>milieu</em> for a blacksmith's son. </p><p>In his fight against social ostracism and professional plagiarism, Smith was forced to sell his fossil collection to the British Museum, lost his house and ended up in debtor's prison. Free again but still homeless, he worked as an itinerant surveyor, until one of his employers recognised him for his work and appointed him Land Steward at an estate near Scarborough. </p><p>Smith later designed the Scarborough Rotunda, one of Britain's oldest surviving purpose-built museums. Only in 1831 was he acknowledged by the Geological Society as the 'Father of English Geology.' His work was an inspiration for Charles Darwin. <br></p>
America beats Britain by 6 years<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzgwMDM5NC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYxMjI3Mjc1MH0.pzG1eZilJm2xlZi6LxHEYk9UBxpRin0xJioQz6wsixA/img.png?width=980" id="9bb7d" class="rm-shortcode" data-rm-shortcode-id="d8f15e9d0604d81112e894350ea08006" data-rm-shortcode-name="rebelmouse-image" alt="\u200bBedrock Geology of the UK and Ireland" />
Bedrock Map of the UK and Ireland, showing science's current understanding of the geology of the islands.
Credit: Geological Survey Ireland<p>William Smith's original map can be visited at the <a href="https://www.geolsoc.org.uk/" target="_blank">Geological Society's headquarters at Burlington House in London</a>, where it hangs side by side with the geological map of England and Wales by George Greenough, the Geological Society's first president and Smith's mapping rival.</p><p>Smith's is an impressive rags-to-fame story, and his accomplishments are now widely acknowledged, thanks in large part by the Simon Winchester book. <br></p><p>However, the brightly shining star of Smith's celebrity somewhat obscures the work of one of his American colleagues. In 1809, six years before Smith published his map, William Maclure produced a geological map of the United States. Although inevitably dubbed the 'Father of American Geology', Maclure has not received the bucketloads of fame (granted, mostly posthumous fame) that Smith did. </p>
Page-turner material<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzgwMDM4NC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0ODg3ODczOH0.V0aPUPqVj1F6kueGrR-8CeGZdpC5lw6yLOZuY8e97l8/img.jpg?width=980" id="97c98" class="rm-shortcode" data-rm-shortcode-id="4b348170695919f3c82ef5d6ce37aae5" data-rm-shortcode-name="rebelmouse-image" alt="A Map of the United States of America. By Samuel G. Lewis. Published In: Observations on the Geology of the United States, explanatory of a Geological Map. By William Maclure." />
Geological map of the United States, by William Maclure (1809). Maclure used an existing map by Samuel G. Lewis as the base map for his color-coded observations.
Image: David Rumsey Map Collection, CC BY-NC-SA 2.0<p>What a difference a star biographer makes. For Maclure's life story sounds like page-turner material too. A successful Scottish merchant, Maclure was rich enough to retire at 34. Settling in Virginia but moving back and forth to Europe, he devoted the rest of his life to science and philanthropy – an example of the latter was his introduction to Philadelphia of educational courses based on the principles of the Swiss innovator Pestalozzi. He later also contributed to the establishment of a utopian community in New Harmony, Indiana. </p><p>Maclure had been bitten by the geology bug on a trip to France. In 1807, he personally started mapping the geology of the then United States, crossing and recrossing the Allegheny Mountains no less than 50 times. The monumental work took him two years to complete. Although he used a different system of classification than Smith, later surveys have confirmed the general accuracy of Maclure's observations.</p><p>In 1817, he became the president of the newly founded Academy of Natural Sciences of Philadelphia, which he would remain almost until his death. Failing health forced him to abandon the attempt to set up an agricultural college in Indiana. He died in Mexico in 1840. In his will he provided for the establishment of 160 working men's libraries. <br></p>
The US is much bigger than in Maclure's day, and geology is much more advanced; yet the current map still builds on some of the observations he made in the early 19th century.
Image: USGS<p><strong></strong><strong>Strange Maps #1046</strong></p><p><em>Got a strange map? Let me know at </em><a href="mailto:firstname.lastname@example.org">email@example.com</a>.<br></p>
A new study finds the rocks that first formed Earth carried with them enough hydrogen for three times the water we have today.
- Enstatite chondrite meteorites are rare today, but they may have been Earth's basic building blocks.
- A study finds these meteorites contain a surprising amount of hydrogen, nitrogen, and water.
- The implication of the study is that Earth had all of its water from the beginning.
Analyzing E chondrites<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzYwNDUwOC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyNzc0NTg1M30.uL0ziiPPOTZud7L_5IXJt2hEKhiX42qcgKoyb9ADOiE/img.jpg?width=980" id="4d974" class="rm-shortcode" data-rm-shortcode-id="3692b2cf3dcba948cedc8c8d42c7a244" data-rm-shortcode-name="rebelmouse-image" alt="enstatite chondrite" />
Credit: User Captmondo/Wikimedia<p>Lead author <a href="http://recherche.crpg.cnrs-nancy.fr/spip.php?rubrique437&lang=fr" target="_blank">Laurette Piani</a> of CPRG <a href="https://source.wustl.edu/2020/08/meteorite-study-suggests-earth-may-have-always-been-wet/" target="_blank">says</a>, "Only a few pristine enstatite chondrites exist: ones that were not altered on their asteroid nor on Earth." In acquiring samples for study, the researchers went out of their way <em>not</em> to select meteorites holding water: "In our study we have carefully selected the enstatite chondrite meteorites and applied a special analytical procedure to avoid being biased by the input of terrestrial water."</p><p>As to why this team of scientists were the first to identify high concentrations of hydrogen in E chondrites, Piani suggests it's due to previous researchers' bias, saying, "it was commonly assumed that these chondrites formed close to the sun. Enstatite chondrites were thus commonly considered 'dry,' and this frequently reasserted assumption has probably prevented any exhaustive analyses to be done for hydrogen." </p><p>Using conventional <a href="https://en.wikipedia.org/wiki/Mass_spectrometry" target="_blank">mass spectrometry</a> and secondary ion mass spectrometry, the scientists did also find water in the meteorites. Recalls Vacher, "The most interesting part of the discovery for me is that enstatite chondrites, which were believed to be almost 'dry,' contain an unexpectedly high abundance of water." In addition to water, the team found substantial amounts of nitrogen they theorize could have aided in the formation of the Earth's atmosphere, nitrogen being its most abundant element.</p>
Earth's first sip<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzYwNDUyMy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1NzM4OTQzMn0.-bEMCDbsCNLfE6A-weKvSN4e8nLeb9wmyNTwXD26XZo/img.jpg?width=980" id="b95b9" class="rm-shortcode" data-rm-shortcode-id="a70443a22a624a53b43a6b335c054240" data-rm-shortcode-name="rebelmouse-image" alt="ocean" />
Credit: gunsan gimbanjang/Shutterstock<p>The researchers were also able to add fresh evidence supporting the theory that E chondrites were Earth's basic building blocks: The meteorites' hydrogen and nitrogen isotopes turned out to be the same as the planet's.</p><p>"Our discovery shows," says Piani, "that the Earth's building blocks might have significantly contributed to the Earth's water. Hydrogen-bearing material was present in the inner solar system at the time of the rocky planet formation, even though the temperatures were too high [at the time] for water to condense." </p><p>Where did our water come from? It was always right here.</p>
According to international law, the seabed belongs to everyone.
Mining the ocean floor for submerged minerals is a little-known, experimental industry.
Seismic data from 2016 reveals a rare bi-directional boomerang earthquake.
- An earthquake ran quickly east before turning west beneath the Atlantic Ocean near the equator in 2016.
- Such earthquakes are likely to pack significantly more destructive power.
- Land-based boomerang earthquakes may have been witnessed, but have never been recorded seismographically.
It was definitely an odd story Rosario García González told in the summer of 2010.
González is an elder of the indigenous Cucapah community in Baja, California/Mexico. He and his wife were in their trailer in Paso Inferior, about 12 miles south-southwest of Mexicali when they heard and felt the distinct, powerful rumble of earthquake moving across their valley. Looking outside, they watched as a cloud of light-colored dust was thrown up into the air along a path going in the opposite direction, as if a truck was retracing the earthquake's path. Except there was no truck.
It's not that scientists didn't believe González's story — they just couldn't figure out what he saw. Could an earthquake possible boomerang? The answer appears to be yes. A new study of seismic data has found clear evidence of another boomerang earthquake — technically a "back-propagating supershear rupture" — that shot back and forth deep beneath the Atlantic Ocean in 2016.
Boom and back
Reconstruction of Romanche fracture zone
The research was conducted by scientists from the University of Southampton and Imperial College, London in the U.K. First author Stephen Hicks of Imperial College says, "Whilst scientists have found that such a reversing rupture mechanism is possible from theoretical models, our new study provides some of the clearest evidence for this enigmatic mechanism occurring in a real fault."
The 2016 magnitude 7.1 quake occurred along the Romanche fracture zone — this is a 559 mile-long fault line near the Atlantic equator, about 650 miles west of the coast of Liberia.
Speaking to National Geographic, Hicks recalled the discovery of what at first seemed like a pair of pulses, which closer examination indicated might actually be two phases of the same quake. If so, the quake zipped eastward, and then west. "This was a weird sort of configuration to see," he says. Confirmation of the boomerang was provided by Ryo Okuwaki of Japan's University of Tsukuba via the identification of seismic echoes from the distant event.
"Even though the fault structure seems simple, the way the earthquake grew was not, and this was completely opposite to how we expected the earthquake to look before we started to analyse the data," admits Hicks.
When modeled, the data collected by 39 seismometers arrayed along the bottom of the ocean-floor gash depicted a temblor that moved rapidly in one direction before suddenly turning around and going back in the other at a blistering 11,000 miles per hour. This likely caused seismic waves to pile up similarly to what happens with air-pressure waves trigger a sonic boom, significantly magnifying the quake's power.
Rosario García González points to where the earthquake doubled back.
Image source: CISESE/USGS
While it's logistically simpler to record and study earthquakes on land thanks to the availability of seismometer networks, land-based temblors tend to track complex fault systems, with geological slips occurring in a series like falling dominoes. Sea-bottom quakes appear to be simpler, making it easier to discern their underlying mechanisms and travels.
Only a few boomerang quakes have ever been recorded, and examples of them on land are virtually nonexistent, making accounts such as González's that much more valuable. Clearly, quakes that double back on themselves stand to do considerably more damage than one-way shakers, allowing more outward propagation of destructive seismic waves in the direction of travel, an amount that would be doubled in a boomerang. Seismologist Kasey Aderhold tells National Geographic that "studies like this help us understand how past earthquakes ruptured, how future earthquakes may rupture, and how that relates to the potential impact for faults near populated areas."
Scientists developing computer models aimed at predicting seismic events haven't thus far been able to create worthy simulations of boomerang quakes, so the details provided the U.K. researchers provide some of the best information yet collected on these geologic oddities.