Category Archive 'Geology'
20 Jul 2018

Welcome to the Meghalayan Age!

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BBC:

The official history of Earth has a new chapter – and we are in it.

Geologists have classified the last 4,200 years as being a distinct age in the story of our planet.

They are calling it the Meghalayan Age, the onset of which was marked by a mega-drought that crushed a number of civilisations worldwide.

The International Chronostratigraphic Chart, the famous diagram depicting the timeline for Earth’s history (seen on many classroom walls) will be updated.

08 Jan 2018

There’s Something Happening Here

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The Landslide Blog has an imminent winner:

Rattlesnake Ridge is a large hillside located above the I-82 highway to the south of the town of Yakima in Washington State, NW USA. The Google Earth image below shows the location of the site (at 46.524, -120.467), taken in May 2017. The image is looking towards the east – note the large active quarry on the south side of the ridge, and other signs of earlier (and smaller scale) excavation on the slope. Note also the proximity of the slope to I-82.

In October 2017 a major fissure started to develop through Rattlesnake Ridge. Over the last three months this apparent tension crack has widened to encompass a volume of about 3 million cubic metres.

The latest reports suggest that the crack is widening at a rate of about 30 cm per week at present. Interestingly KIMA TV reports that the expectation is that the slope will self-stabilise:

    Senior Emergency Planner Horace Ward said they have not determined a cause yet and said it’s just nature. Ward said the ridge is being monitored and they think the slide will stop itself.

    “It could continue to move slowly enough to where it kind of just keeps spilling a little bit of material into the quarry until it creates a toe for itself to stop and stabilize the hillside,” he said.

The implication of this is that it is a rotational slip. However, the tension crack has quite a complex structure, with some evidence of the development of a graben structure.

RTWT

07 Aug 2017

Criticizing Tolkien’s Map

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Alex Acks is a geologist who thinks J.R. Tolkien, where geology is concerned, is an excellent scholar of linguistics.

I’m good with the mountain ranges on the west coast of the map. I can pretend that Eriador is like the California of Middle-earth, and it’s a nice active margin—I will just ignore that my housemate, who unlike me has completed the Silmarillion slog, has disabused me of that notion. And I can buy the placement of the Misty Mountains, again as a continent-continent collision, perhaps, even if there should be a lot more shenanigans going on then, in terms of elevation. But when you throw in the near perpendicular north and south mountain ranges? Why are there corners? Mountains don’t do corners.

And Mordor? Oh, I don’t even want to talk about Mordor.

Tectonic plates don’t tend to collide at neat right angles, let alone in some configuration as to create a nearly perfect box of mountains in the middle of a continent. I’ve heard the reasoning before that suggests Sauron has made those mountains somehow, and I suppose right angles are a metaphor for the evil march of progress, but I don’t recall that being in the books I read. And ultimately, this feels a lot like defending the cake in the song MacArthur Park as a metaphor—okay fine, maybe it’s a metaphor…but it’s a silly metaphor that makes my geologist heart cry tears of hematite.

Mount Doom, I’m more likely to give a pass to, since it’s obviously a place of great magic. But geologically, it posits a mantle plume creating a hot spot under Mordor—since that’s the only way you’re going to get a volcano away from subduction or rifting zones, and I’ve already called shenanigans on Mordor being either of those. And the hallmark of hot spot volcanism is that you get chains of volcanoes, with the youngest being the active volcano and the older ones normally quiescent. This is caused by the tectonic plates moving over the hot spot; examples include the Juan Fernández Ridge, the Tasmantid Seamount Chain, and the Hawaiian Islands (more properly called the Hawaiian-Emperor seamount chain). You’ll notice most hot spots can be found in the oceans, because there’s more ocean on Earth than land, and also the crust is thinner there, so a hot spot causes volcanism much more readily. On continents, you’re more likely to get dike swarms (e.g.: the Mackenzie dike swarm in Nunavet, Canada) where magma filters into cracks and weak spots between formations and remains underground until unroofed by erosion—or chains of massive volcanic calderas like the ones you see ranging from Yellowstone to the Valles Caldera in the US.

Okay, so maybe Mount Doom is from a really young hot spot and there’s been no drift since it started. That’s the best I’ve got for you. It’s better than the nonsensical border mountains.

10 Jun 2014

Largest Alluvial Gold Nugget

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WelcomStrangerNugget
(Image: Museum of Victoria)

earthstory: This is the Welcome Stranger Nugget.

Discovered in 1869 by Cornishmen John Deason and Richard Oates in Victoria, Australia, it is the largest gold nugget ever discovered.

It weighed in at 69kg (152.1 lb.) and measured 61x31cm (24×12.2″) and it was found just a couple of metres below the surface.

At the time no scale was big enough to weight the nugget so it was broken into 3 pieces and each piece weighed separately.

At today’s Gold Value the nugget would be worth

$3,786,257.01 AUD (Correct 21/09/2012 Perth Royal Mint)

To read more:

Museum Victoria

Australia Historical Finds and Discoveries

Australian Gold

VisitMaryBorough.com

Via Ratak Monodosico.

25 Feb 2014

Best Craters

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My Science Academy:

Xico volcano sits at the extreme southern end of the Mexico City megalopolis. For a geologically significant chunk of time, this area was underwater, drowned by Lake Chalco. The lake began to dry out in the 1300s, and Aztec fishermen settled along its coastline hereabouts. In the nineteenth century, the government drained the lake entirely; the fishermen were awarded communal land grants and told to become farmers.

Farming became intensive in the 1970s, when corporate agriculturists and desperate landless peasants struck illegal or quasi-legal deals with the communal organizations and wrested control of the rich volcanic soil. Thousands and thousands of families poured into the region, hoping for work. Farmers climbed over the rim of the volcano and plowed fields inside the crater. Xico the town sprawled right up to the ramparts of Xico the crater and appears likely to soon engulf it; in 2005, the population of the municipality was 330,000.

And 9 more.

Hat tip to Ratak Monodosico.

08 Nov 2012

100 Million Year Old Geology Created Some of Today’s Rock-Ribbed Democrat Counties

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A line of blue counties stretches across the usually red-voting South which parallels curiously enough an ancient sea coast from 100 million years ago. Why?

Dr. M. explains:

Hale County in west central Alabama and Bamberg County in southern South Carolina are 450 miles apart. Both counties have a population of 16,000 of which around 60% are African American. The median households and per capita incomes are well below their respective state’s median, in Hale nearly $10,000 less. Both were named after confederate officers–Stephen Fowler Hale and Francis Marion Bamberg. And although Hale’s county seat is the self-proclaimed Catfish Capitol, pulling catfish out of the Edisto River in Bamberg County is a favorite past time. These two counties share another unique feature. Amidst a blanket of Republican red both Hale and Bamberg voted primarily Democratic in the 2000, 2004, and again in the 2008 presidential elections. Indeed, Hale and Bamberg belong to a belt of counties cutting through the deep south–Mississippi, Alabama, Georgia, South Carolina, and North Carolina–that have voted over 50% Democratic in recent presidential elections. Why? A 100 million year old coastline.

During the Cretaceous, 139-65 million years ago, shallow seas covered much of the southern United States. These tropical waters were productive–giving rise to tiny marine plankton with carbonate skeletons which overtime accumulated into massive chalk formations. The chalk, both alkaline and porous, lead to fertile and well-drained soils in a band, mirroring that ancient coastline and stretching across the now much drier South. This arc of rich and dark soils in Alabama has long been known as the Black Belt. But many, including Booker T. Washington, coopted the term to refer to the entire Southern band. Washington wrote in his 1901 autobiography, Up from Slavery, “The term was first used to designate a part of the country which was distinguished by the color of the soil. The part of the country possessing this thick, dark, and naturally rich soil…”

Cretaceous rock units (139-65 million years old) are shown in shades of green. Older rock units are in gray, younger ones in yellow. From Geology and Election 2000.

Over time this rich soil produced an amazingly productive agricultural region, especially for cotton. In 1859 alone a harvest of over 4,000 cotton bales was not uncommon within the belt. And yet, just tens of miles north or south this harvest was rare. Of course this level of cotton production required extensive labor.

As Washington notes further in his autobiography, “The part of the country possessing this thick, dark, and naturally rich soil was, of course, the part of the South where the slaves were most profitable, and consequently they were taken there in the largest numbers. Later and especially since the war, the term seems to be used wholly in a political sense—that is, to designate the counties where the black people outnumber the white.”

Readers can compare 2012 results using individual state maps at Politico.

25 Mar 2011

The Scientific Swindler (1884-1891)

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A scientific swindler preyed on American scientists working in Geology during a period extending from 1884 to 1891, obtaining books, specimens, and money from a number of American scholars. He had a good knowledge of Eastern European languages, was well acquainted with the field and frequently assumed the names of prominent authorities. By the time he vanished from history, he had also accurately identified large numbers of specimens in American museum collections.

14 Jul 2010

The Left’s Latest Target

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Serpentine

Newly arrived on the enemies list of the perennially concerned is California’s state rock, serpentine. A bill to oust serpentine is making its way through the California State Legislature, and geologists are flocking to the Magnesium Iron Silicate Hydroxide’s defense.

The bill to defrock the rock — which recently passed the full State Senate and is awaiting a vote in the Assembly — is sponsored by Senator Gloria Romero, a Los Angeles Democrat, with the strong support of the Asbestos Disease Awareness Organization.

Declaring that serpentine “has known health effects,” the bill would leave California — one of roughly half the states in the nation with an official rock or mineral — without an official rock. (According to the bill, California was the first state, in 1965, to name an official rock.) Asbestos occurs naturally in many minerals, and indeed some serpentine rocks do serve as a host for chrysotile, a form of asbestos. But geologists say chrysotile is less harmful than some other forms of asbestos, and would be a danger — like scores of other rocks — only if a person were to breathe its dust repeatedly.

“There is no way anyone is going to get bothered by casual exposure to that kind of rock,” said Malcolm Ross, a geologist who retired from the United States Geological Survey in 1995. “Unless they were breaking it up with a sledgehammer year after year.”

Dr. Ross and other opponents of the bill are concerned that removing serpentine, which is occasionally used in jewelry, as the state’s rock would demonize it and thus inspire litigation against museums, property owners and other sites where the rocks sit; they cite the inclusion of a letter of support from the Consumer Attorneys of California with the bill as evidence.

“If they keep the asbestos issue bubbling,” Dr. Ross said, “it means money for politicians, more money for lawyers and money for scientists to investigate.”

J. D. Preston, a spokesman from the consumer lawyers group, said the group had nothing to do with drafting the legislation and was just responding to a request from the awareness organization for a support letter. “We just thought this was a good fit in our mission of consumer safety,” Mr. Preston said. “It is certainly not the intent, and we don’t even see where it opens the avenue for litigation.”

Gov. Arnold Schwarzenegger has indicated no position.

We were unable to interview Virginia’s state rock, as none has ever been appointed. Virginia’s state fossil Chesapecten jeffersonius, being naturally conservative, expressed mild chagrin at California’s radical politics, but was happy that California is so far away.

16 Jul 2009

Can the Alleged Consensus Actually be Wrong?

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ScienceFair reads a new journal article in Nature Geoscience and begins to wonder.

Could the best climate models — the ones used to predict global warming — all be wrong?

Maybe so, says a new study published online today in the journal Nature Geoscience. The report found that only about half of the warming that occurred during a natural climate change 55 million years ago can be explained by excess carbon dioxide in the atmosphere. What caused the remainder of the warming is a mystery.

“In a nutshell, theoretical models cannot explain what we observe in the geological record,” says oceanographer Gerald Dickens, study co-author and professor of Earth Science at Rice University in Houston. “There appears to be something fundamentally wrong with the way temperature and carbon are linked in climate models.”

During the warming period, known as the “Palaeocene-Eocene thermal maximum” (PETM), for unknown reasons, the amount of carbon in Earth’s atmosphere rose rapidly. This makes the PETM one of the best ancient climate analogues for present-day Earth.

As the levels of carbon increased, global surface temperatures also rose dramatically during the PETM. Average temperatures worldwide rose by around 13 degrees in the relatively short geological span of about 10,000 years.

The conclusion, Dickens said, is that something other than carbon dioxide caused much of this ancient warming. “Some feedback loop or other processes that aren’t accounted for in these models — the same ones used by the Intergovernmental Panel on Climate Change for current best estimates of 21st century warming — caused a substantial portion of the warming that occurred during the PETM.”

Abstract:

The Palaeocene–Eocene Thermal Maximum (about 55 Myr ago) represents a possible analogue for the future and thus may provide insight into climate system sensitivity and feedbacks. The key feature of this event is the release of a large mass of 13C-depleted carbon into the carbon reservoirs at the Earth’s surface, although the source remains an open issue. Concurrently, global surface temperatures rose by 5–9 °C within a few thousand years. Here we use published palaeorecords of deep-sea carbonate dissolution, and stable carbon isotope composition, along with a carbon cycle model to constrain the initial carbon pulse to a magnitude of 3,000 Pg C or less, with an isotopic composition lighter than minus50permil. As a result, atmospheric carbon dioxide concentrations increased during the main event by less than about 70% compared with pre-event levels. At accepted values for the climate sensitivity to a doubling of the atmospheric CO2 concentration1, this rise in CO2 can explain only between 1 and 3.5 °C of the warming inferred from proxy records. We conclude that in addition to direct CO2 forcing, other processes and/or feedbacks that are hitherto unknown must have caused a substantial portion of the warming during the Palaeocene–Eocene Thermal Maximum. Once these processes have been identified, their potential effect on future climate change needs to be taken into account.

25 Jun 2009

Sarychev Peak, Kuril Islands

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Just by good luck, the International Space Station happened to be passing over Sarychev Peak on Matua Island in the Kuril Islands on June 12th at the perfect time to allow astronauts to photograph its volcanic eruption.

NASA Earth Observatory

Hat tip to Karen L. Myers.

05 Jan 2009

Alarm Over Increased Seismic Activity at Yellowstone

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You won’t need to worry about Global Warming if the Yellowstone Caldera decides to erupt.

London Times:

Hundreds of earthquakes have hit Yellowstone National Park, raising fears of a more powerful volcanic eruption.

The earthquake swarm, the biggest in more than 20 years, is being closely monitored by scientists and emergency authorities.

The series of small quakes included three last Friday which measured stronger than magnitude 3.0. The strongest since this latest swarm of quakes began on December 27 was 3.9.

No damage has yet been reported but scientists say this level of activity – there have been more than 500 tremors in the last week – is highly unusual.

“The earthquake sequence is the most intense in this area for some years,” said the Yellowstone Volcano Observatory. Some of the larger earthquakes have been felt by park employees and guests, according to the observatory.

The swarm is occurring beneath the northern part of Yellowstone Lake in the park. Yellowstone sits on the caldera of an ancient supervolcano and continuing geothermal activity can be seen in the picturesque geysers and steam holes, such as Old Faithful.

About 1,000 to 2,000 tremors a year have been recorded since 2004. …

Professor Robert B. Smith, a geophysicist at the University of Utah and one of the leading experts on earthquake and volcanic activity at Yellowstone, said that the swarm was significant.

“It’s not business as usual,” he said. “This is a large earthquake swarm, and we’ve recorded several hundred. We are paying careful attention. This is an important sequence.”

The last full-scale explosion of the Yellowstone Supervolcano, the Lava Creek eruption which happened approximately 640,000 years ago, ejected about 240 cubic miles of rock and dust into the sky.

Geologists have been closely monitoring the rise and fall of the Yellowstone Plateau as an indication of changes in magma chamber pressure.

The Yellowstone caldera floor has risen recently – almost 3in per year for the past three years – a rate more than three times greater than ever observed since such measurements began in 1923.

From mid-summer 2004 through to mid-summer 2008, the land surface within the caldera moved upwards as much as 8in at the White Lake GPS station. The last major earthquake swarm was in 1985 and lasted three months.

USGS Yellowstone Volcano Observatory site

Map of recent earthquakes

03 Dec 2008

New Carbon Dating of Thera Produces Archaeological Puzzle

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Recent carbon dating tests of the Thera Eruption provides a date contradicting the established chronological sequence of Egyptian and Cypriot pottery found on the island.

www.an.gr:

Two olive branches buried by a Minoan-era eruption of the volcano on the island of Thera (modern-day Santorini) have enabled precise radiocarbon dating of the catastrophe to 1613 BC, with an error margin of plus or minus 10 years, according to two researchers who presented conclusions of their previously published research during an event on Tuesday at the Danish Archaeological Institute of Athens.

Speaking at an event entitled “The Enigma of Dating the Minoan Eruption – Data from Santorini and Egypt”, the study’s authors, Dr. Walter Friedrich of the Danish University of Aarhus and Dr. Walter Kutschera of the Austrian University of Vienna, said data left by the branch of an olive tree with 72 annular growth rings was used for dating via the radiocarbon method, while a second olive branch — found just nine metres away from the first — was unearthed in July 2007 and has not yet been analysed. …

On the other hand, as the two researchers pointed out, archaeological evidence linked with the Historical Dating of Ancient Egypt indicate that the Thera eruption must have occurred after the start of the New Kingdom in Egypt in 1530 BC.

The two researchers said their find (olive tree) represents a serious contradiction between the results of the scientific method (radiocarbon dating) and scholarly work in the humanities (history-archaeology), with both sides holding strong arguments to support their conclusions.

The radiocarbon dating places the cataclysmic eruption, blamed for heralding the end to the Minoan civilisation, a century earlier than previous scientific finds.

The eruption and the subsequent devastation throughout the Aegean has long piqued researchers’ interest, with many scholars pointing to Plato’s reference of the “lost continent of Atlantis” on vague memories, passed down generation to generation in the ancient Greek world, of the catastrophe.

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