A Revolution in Plate Tectonics?

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Camster (Rhymes with Hamster)

Social climber
CO
Dec 23, 2014 - 12:24pm PT
1955, I believe.

You're right. Sam Carey was considered a heretic by many geologists around the world. My father was mentored by Sam and his friend Alan Voisey. My father and his friend, Mike Rickard, put the orocline theory to the test. See: http://publications.americanalpineclub.org/articles/12199402000/Patagonian-Orocline-Expedition1967-68

I remember in the mid-1980s when I was working for a company doing mineral and oil searching in New Guinea (the company was based in North Sydney). I could mention my father's name, or Carey's, or Voisey's, and it would draw a reaction from everyone in the office.

More here: http://en.wikipedia.org/wiki/Orocline
Chiloe

Trad climber
Lee, NH
Topic Author's Reply - Dec 23, 2014 - 03:14pm PT
Interesting work, Cam, I wasn't aware of that history. Sounds like you had a front-row seat.
Camster (Rhymes with Hamster)

Social climber
CO
Dec 23, 2014 - 03:38pm PT
Uh, yeah. With my father, life is definitely a full-contact sport.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Dec 23, 2014 - 07:17pm PT
Interesting paper Cam...thanks for posting it. Some of the crustal rotations (e.g., counter clockwise rotation of the Iberian Peninsula) mentioned were later proven to be correct using paleomagnetism.

Eldridge Moores, mentioned up thread by DMT, was another influential individual who helped bring about the paradigm shift in geologic thought that lead to plate tectonics. Moores was an early pioneer of ophiolite sequences and their regional structural implications, including the Troodos ophiolite in Cyprus and later the Smartville Complex in the Sierra foothills. With tremendous imagination, Moores and others recognized that ultra-mafic rocks originating in the mantle had been obducted on to the continent and they began describing sequences of tectonic events to explain the structural relationships and petrographic observations.

Ophiolite sequence from Elements Vol 10 Apr 2014 Ophiolites and Their Origin by Yildirim Dilek and Harald Furnes

An ophiolite is, therefore, a suite of temporally and spatially associated ultramafic, mafic, and felsic rocks that formed as the products of multiple mantle melting events and magmatic differentiation processes in a particular tectonic environment.

Possible schematic time-series for emplacement of an ophiolite sequence on the continent
Todd Eastman

climber
Bellingham, WA
Dec 23, 2014 - 07:19pm PT
Earth shattering news!
Chiloe

Trad climber
Lee, NH
Topic Author's Reply - Feb 17, 2015 - 06:01pm PT
From a talk I saw today, this was news to me. You 'ologists and desert lovers out there already know what the Kaibab, Coconino and Supai formations are doing in this picture from the eastern Mojave?

eeyonkee

Trad climber
Golden, CO
Feb 17, 2015 - 07:12pm PT
Lying unconformably on top of or in low-angle normal fault contact with much older, metamorphic rocks? Is that a detachment fault beneath the Supai?
Chiloe

Trad climber
Lee, NH
Topic Author's Reply - Feb 17, 2015 - 08:24pm PT
Lying unconformably on top of or in low-angle normal fault contact with much older, metamorphic rocks?

That's what I would have guessed too but there's more tectonics in the story now. The Grand Canyon strata here have been strongly metamorphosed themselves, by proximity to the shallowly subducting (and water-rich) Pacific plate immediately below the eastern Mojave. And twisted up as well, the K and S letters at upper right in that slide point out Kaibab and Supai formations too.

Is that a detachment fault beneath the Supai?

In the Grand Canyon, the Supai rests atop Redwall Limestone, which forms handsome 150-meter cliffs that are one of the Canyon's most notable features. Here in the eastern Mojave it's still atop what used to be Redwall Limestone -- but that's been metamorphosed to marble, and sheared to less than half a meter thick. You could span the whole Redwall (what's left of it) with your hands. So most of the GC strata apparently are represented here but in much altered form.
eeyonkee

Trad climber
Golden, CO
Feb 18, 2015 - 10:36am PT
I've seen that attenuated section at the Big Marias. Went on a field trip when I was attending San Diego State back in the late 1970s.
Chiloe

Trad climber
Lee, NH
Topic Author's Reply - Feb 24, 2015 - 01:07pm PT
I think BASE posted something about the Midcontinent or Keweenawan Rift here a few days back but it seems to have disappeared. Hopefully he can drop in again to say more.

Lake Superior today occupies part of this rift. Wikipedia has this intriguing description,
The Midcontinent Rift is the deepest closed or healed rift yet discovered; no known deeper rift ever failed to become an ocean.

So why did this mid-continental rift fail? One (revolutionary) theory is that plate tectonics in its modern form was not yet under way, that long ago (1.1 Ga).
Chiloe

Trad climber
Lee, NH
Topic Author's Reply - Feb 25, 2015 - 10:26am PT
Here's another idea that's so old it is new again: Did the Moon once have actual seas? The orthodox "dry Moon" model says it did not, but there's a dissenting view, varied evidence, and (what seems to me) a really strong logical argument why it probably did have seas once, back around 4 Ga.

Some discussion of this idea, and other lunar heresies, appears in a forthcoming paper by O'Hara and Niu, "Obvious problems in lunar petrogenesis and new perspectives," which has been accepted but not yet published for a forthcoming Geological Society of America volume on The Interdisciplinary Earth.

Recent success in the determination of abundant water in lunar glasses and minerals confirms the prediction in the early days of lunar research that the Moon may have been a water-rich planet and may still be so in its interior, which disfavours the dry Moon hypothesis, weakens the LMO [lunar magma ocean] hypothesis, and questions many related lunar petrogenesis interpretations.

So there is mineralogical evidence for a formerly water-rich Moon, and this challenges the conventional wisdom in many ways. Is there geological evidence for water as well? There are several ways to look for this, which another forthcoming paper will do.
Chiloe

Trad climber
Lee, NH
Topic Author's Reply - Mar 6, 2015 - 01:58pm PT
Back in December I wrote about seeing a poster at the AGU meetings about The Seven Ocean Worlds. To recap,

A new concept for me -- the Seven Ocean Worlds:
Earth
Ceres
Callisto
Ganymede
Europa
Enceladus
Titan

Folks are making their pitch for these to be a new focus of exploration, competing with other places (namely Mars, and exoplanet spectroscopy) for limited NASA resources. It's claimed the ocean worlds are the most likely places in the solar system to find life. And sampling the water from at least one of them might be easier than I thought: Enceladus has more than 100 active ice volcanoes spraying it into space, where an orbiter could capture and taste water from a truly alien sea.

As anyone interested enough to click on this thread probably knows already, NASA has a space probe that went into orbit around Ceres today. The asteroid or dwarf planet Ceres looks like this, with its curious bright spots:


Prime topics for investigation by the Dawn probe will be evidence of water vapor, comet-like sublimation of ice (or salts left behind) and indications for a subsurface ice mantle or sea.
Chiloe

Trad climber
Lee, NH
Topic Author's Reply - Mar 6, 2015 - 02:31pm PT
Yah, my hidden agenda here is a tricky one. And would you believe, there's a connection between Ceres and earthly plate tectonics? Or at least, in my version of the story.

Which will eventually bring the Moon, Mars and Venus back as well. Hey that sounds crackpot, but the key paper (not mine!) has now passed final review and should soon be in press.
Chiloe

Trad climber
Lee, NH
Topic Author's Reply - Mar 6, 2015 - 02:34pm PT
As a geology-curious soul you're most welcome on this thread! Conspiracies and all.
Chiloe

Trad climber
Lee, NH
Topic Author's Reply - Mar 6, 2015 - 03:28pm PT
Recent discoveries of water ice sublimating from Ceres, currently guessed to be a comet-like (solar heated) process, add to the evidence that Ceres has lots of ice if not water. Maybe a significant fraction (10% ?) relative to the water in Earth's oceans. We'll soon know more about how that's related to the bright spots seen by Dawn.


Perhaps it's related to something closer to home, as well: the origin of Earth's oceans.
Oplopanax

Mountain climber
The Deep Woods
Nov 30, 2015 - 04:49pm PT
http://www.scientificamerican.com/article/geologists-confirm-mantle-plumes-generate-volcanic-hotspots/
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Nov 30, 2015 - 09:19pm PT
Here's the abstract for the Nature article mentioned above...note deep origin of hotspots at 1,000 kms

Broad plumes rooted at the base of the Earth's mantle beneath major hotspots

Scott W. French & Barbara Romanowicz

Nature 525, 95–99 (03 September 2015) doi:10.1038/nature14876
Received 12 November 2014 Accepted 19 June 2015 Published online 02 September 2015

Plumes of hot upwelling rock rooted in the deep mantle have been proposed as a possible origin of hotspot volcanoes, but this idea is the subject of vigorous debate. On the basis of geodynamic computations, plumes of purely thermal origin should comprise thin tails, only several hundred kilometres wide, and be difficult to detect using standard seismic tomography techniques. Here we describe the use of a whole-mantle seismic imaging technique—combining accurate wavefield computations with information contained in whole seismic waveforms—that reveals the presence of broad (not thin), quasi-vertical conduits beneath many prominent hotspots. These conduits extend from the core–mantle boundary to about 1,000 kilometres below Earth’s surface, where some are deflected horizontally, as though entrained into more vigorous upper-mantle circulation. At the base of the mantle, these conduits are rooted in patches of greatly reduced shear velocity that, in the case of Hawaii, Iceland and Samoa, correspond to the locations of known large ultralow-velocity zones. This correspondence clearly establishes a continuous connection between such zones and mantle plumes. We also show that the imaged conduits are robustly broader than classical thermal plume tails, suggesting that they are long-lived, and may have a thermochemical origin. Their vertical orientation suggests very sluggish background circulation below depths of 1,000 kilometres. Our results should provide constraints on studies of viscosity layering of Earth’s mantle and guide further research into thermochemical convection.
Reilly

Mountain climber
The Other Monrovia- CA
Nov 30, 2015 - 10:04pm PT
There was an article in the LA Times Sunday talking about how all the heavy
metals that have been 'brought' to the Earth by impact are responsible for
the Moon's orbit which is not co-planar with the Earth's around the Sun.
The study's authors said that if all those metals had not arrived here the
Moon's orbit would be co-planar and a total eclipse would occur each month!
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Nov 30, 2015 - 11:05pm PT
Here's how I understand it Reilly...
Au, a siderophile element in the primordial earth migrated to the Fe, Ni core in early earth history when the earth differentiated into core, mantle and crust (> 4 billion years ago). The early crust would have been depleted in these siderophile elements. Later impacts (< 4 billion years ago) brought heavy metals, including Au, to the earth's crust. Without these later impacts, Au would not be accessible at or near the earth's surface. These heavy metals have been recycled and concentrated in ore deposits in granitic and volcanic rocks via plate tectonics starting about 2.5-3 billion years ago. The moon was originally in an equatorial orbit but it was slightly knocked off this orbit by large objects that passed through the solar system but ended up somewhere else.

Here's the NYT article...
Scientists Link Moon’s Tilt and Earth’s Gold
By KENNETH CHANGNOV. 27, 2015

The moon’s orbit is askew, and two planetary scientists believe that they have come up with a good reason.


Intriguingly, their idea also explains why gold and platinum are found in the Earth’s crust, well within diggable reach.

The moon is believed to have formed out of a giant cataclysmic collision early in the history of the solar system when an interplanetary interloper the size of Mars slammed into Earth and lofted a ring of debris circling over the Equator. The debris coalesced into the moon.

At its birth, the moon was quite close to the Earth, probably within 20,000 miles. Because of the tidal pulls between the Earth and moon, the moon’s orbit has slowly been spiraling outward ever since, and as it does, Earth’s pull diminishes, and the pull of the sun becomes more dominant.

By now, with the moon a quarter million miles from Earth, the sun’s gravity should have tipped the moon’s orbit to lie in the same plane as the orbits of the planets.

But it has not. The moon’s orbit is about 5 degrees askew.

“That the lunar inclination is as small as it is gives us some confidence that the basic idea of lunar formation from an equatorial disk of debris orbiting the proto-Earth is a good one,” said Kaveh Pahlevan, a planetary scientist at the Observatory of the Côte d’Azur in Nice, France. “But the story must have a twist.”

Writing in this week’s issue of the journal Nature, Dr. Pahlevan and his observatory colleague Alessandro Morbidelli propose the twist.

The moon did indeed form in the Earth’s equatorial plane, the scientists said, but then a few large objects, perhaps as large as the moon, zipping through the inner solar system repeatedly passed nearby over a few tens of millions of years and tipped the moon’s orbit.

A series of computer simulations show that the idea is plausible.

“This mechanism works for a broad range of physical conditions,” Dr. Pahlevan said.

Eventually the crisscrossing mini-planets would have been tossed out of the solar system, swallowed by the sun, or slammed into the Earth or the other planets.

Robin M. Canup, a planetary scientist at the Southwest Research Institute in Boulder, Colo., who wrote an accompanying commentary in Nature, said the thousands of close passes that typically occur before an impact were a “really new realization” by Dr. Pahlevan and Dr. Morbidelli.

“While a single scattering event will only change the moon’s tilt slightly,” Dr. Canup said, “it’s the cumulative effect of these many passes that can produce this tilt.”

The scars of one or more moon-size objects hitting Earth would have long been erased by the tectonics of the shifting surface, but those impacts would explain the gold, platinum and other precious metals in the Earth’s crust but not on the moon.

Metals on the early Earth should have sunk to the interior. Thus, planetary scientists think that after the moon was created, later collisions that provided the last 1 percent or so of the Earth’s mass added a veneer of precious metals.

A dearth of lunar metals argues for a few large metal-rich objects hitting the Earth rather than many small ones.

The computer simulations show that the chances of the moon’s getting hit are low. In the simulations, if there was one object buzzing by, the moon was hit 9 percent of the time. With four objects, the chances of a lunar impact rose to 25 percent.

“Not an overly likely outcome, which is good,” Dr. Canup said.

Scientists including Dr. Canup had proposed other explanations for the tilt. “I would say those relied on certainly more complex processes and required rather narrow sets of conditions for success,” Dr. Canup said. “I think where this has really stepped in is it’s a very simple mechanism.
clifff

Mountain climber
golden, rollin hills of California
Dec 1, 2015 - 12:02pm PT
How is the Long Valley Caldera super volcano explained? Along with Sierra Valley and Yellowstone there is an arc of 3 supervolcanos, must be connected somehow?

mysterious stone columns along Crowley Lake

http://www.latimes.com/science/la-me-adv-volcanic-columns-mystery-20151115-story.html


--------------------------------------


Subterranean worms from hell

New species of nematode discovered more than a kilometre underground.

http://www.nature.com/news/2011/110601/full/news.2011.342.html

http://www.manyworlds.space/index.php/2015/11/24/many-worlds-subterranean-edition/
Messages 141 - 160 of total 170 in this topic << First  |  < Previous  |  Show All  |  Next >  |  Last >>
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