Trovants - growing, moving, multiplying, and generating bunk?

[FatPhil]

I can't say I'd ever heard of trovants before today, and they seem to be surrounded by weaselly-worded and indirect ("some say ...") claims that at least seem bunklike.

StartPage search results for just the word trovant (so the line below the URL is the page title as scraped by the search engine)

https://science.howstuffworks.com/environmental/earth/geology/trovants.htm
Trovants Are Stones That Seem to Grow, Move and Reproduce

https://whenonearth.net/trovants-growing-stones-romania/
Trovants - The Mysterious Growing Stones of Romania

https://wonderopolis.org/wonder/Are-Trovants-Alive
Are Trovants Alive? - Wonderopolis

https://indie88.com/trovants-are-the-mysterious-living-stones-of-romania/
Trovants Are The Mysterious 'Living' Stones Of Romania - Indie88

https://www.sciencealert.com/these-strange-bulging-geological-manifestations-loom-over-romania
These Eerie 'Living Stones' in Romania Are Fantastical, And Totally ...

https://www.geologyin.com/2018/04/the-mysterious-living-stones-of-romania.html
The Mysterious Living Stones of Romania: They Grow and Move

... and many more.

Drilling down:
The "growing" claim seems to be little more than "once exposed to the elements, over a time-span of centuries to millennia, some of the inner minerals can expand and leach out to the surface forming bumps", with no evidence that this process continues.

... after a heavy rain small forms are said to appear on the rocks leading them to be dubbed the "growing stones" by locals.
... can appear to grow at times, as if they are alive.
... after a heavy rain small stone forms are said to appear on the rocks leading them to be dubbed as the "growing stones".

-- https://www.geologyin.com/2018/04/the-mysterious-living-stones-of-romania.html

The "multiplying/reproducing" claim seems to be little more than a photo that to me looks like several have grown together like overlapping crystals, which is being interpreted as one growing out of another.

(ibid.)

The "moving" claim could easily be explained by Romania being geologically active.

Recent earthquakes and their magnitudes in Romania - Worlddata.info
In Romania, there are partly large earthquakes with strengths of more than 7.0

-- https://www.worlddata.info/europe/romania/earthquakes.php

The page I've quoted seems the sanest of the ones that I've seen, but it still carries the implications that seem like bunk to me - where do they get their silicon from, when they "grow"? That doesn't come from the rain.

This guy makes a claim that a small nugget he holds in his hand will grow into something human-sized:

Source: https://www.youtube.com/watch?v=InwT_7kvO1A

Visiting The Growing Stones | Trovants - YouTube

None of the claims are accompanied by any before/after evidence. It seems as if they're so slowly changing that such evidence doesn't even exist. Everything seems to just be interpretation and extrapolation. Sure, they're an interesting curiosity, but I think they're also a bunk-magnet. Can any geologists shed any light on the matter?

Sorry it this appears a hastily-formed post - I've just been summoned to lunch, and my browser has an annoying habit of losing work in progress, so I thought it's better to post half a thread-starter than have to do over.

 

[Ann K]

Leaving aside some of the more fantastic claims, "Science Alert" appears to have a more factual description and explanation.

Likely shaped by earthquakes around 6 million years ago, Trovants are concretion sedimentary sand grains or rocks bound together by limestone (calcium carbonate) cement. "Some are made from sandstone, others from gravel," Buila-Vanturarita National Park manager Florin Stoican told Radio Romania International back in 2010. "In geological terminology, they are made from gritstone and conglomerates."

Researchers have found no difference between the Trovants and the surrounding sand substrate. So they suspect the spheroid shapes were formed by the unusually long-lasting and intense seismic activity of the Middle Miocene. Shockwaves from the earth compacted the sandy sediments and concentrated the limestone cement to mold their spherical lumps.

Over time, the elements wore away the looser sandstone around them, exposing the denser trovants.

When exposed to heavy rains, some of their cement can leak out to their surface, gradually adding to the stone's outer circumference over time. Not much has been written about this process, but it is said to occur at only about 4-5 cm over 1,200 years.

The surrounding sandstone beds have laminations - a sequence of fine layering - suggesting the area was an ancient marine environment when the stones and base sediment were laid down, as do the bivalve and gastropod fossils that can be found within some of the trovants.

https://www.sciencealert.com/these-strange-bulging-geological-manifestations-loom-over-romania

 

[FatPhil]

When exposed to heavy rains, some of their cement can leak out to their surface, gradually adding to the stone's outer circumference over time. Not much has been written about this process, but it is said to occur at only about 4-5 cm over 1,200 years.

Yeah, I was going to include that quote - it jumped out at me as being a strange statistic. Why measure things over a 1200 year span? That seems strangely precise. How do you measure things over a 1200 year span? How do you know the guy who was measuring things 1200 years ago was measuring exactly what you're measuring now? You have to remember that Pi was 3 only a few millennia back.
(And notice the "said to" don't-blame-me-I'm-just-the-messanger weasel wording. All that I know for sure is that he's called "The Stig".)

 

[psikiwi]

I can't say I'd ever heard of trovants before today, and they seem to be surrounded by weaselly-worded and indirect ("some say ...") claims that at least seem bunklike.

Thanks for the heads-up on an unusual phenomenon. I'd also never heard of Trovants, and I've no idea on the etymology, but as soon as I saw the image, it struck me as 'concretion' formations. I have to agree that there are some weaselly words in there: being charitable, this is simply hyperbole to bring in the tourists/ garner clicks.

Growing up not far from Mangaweka, in the lower central North Island, New Zealand, the local landscape was defined by cliffs carved through the soft sandstone by the Rangitikei river. (The road and single-track suspension bridge in the lower central part, and winding up the lower right side was my daily ride on the school bus ride...)

https://teara.govt.nz/en/rock-and-mineral-names/page-1

Papa

The terms papa or papa-rock are used for the widespread soft, blue-grey mudstone or muddy sandstone.
Although the word papa is of Māori derivation (meaning earth), by the mid-19th century it was being used by Pākehā writers referring to mudstone, and in 1905 it was nicely summed up: 'The Papa Rock, of which many of the cliffs in the bush country of New Zealand are formed, is really a very hard, blue clay … It lies in distinct strata, and when the wet penetrates to one beneath, the surface of this latter becomes as slippery as glass'. 1

And from the side-bar there:

Soft rock

The rock known as papa was deposited on the sea floor over the last 15 million years, then later uplifted. It is relatively soft because it has never been deeply buried or compacted. For engineering purposes, papa is classified as 'soft rock' or 'engineering soil' because it has the physical properties of unconsolidated soil rather than rock.

Researchers have found no difference between the Trovants and the surrounding sand substrate. So they suspect the spheroid shapes were formed by the unusually long-lasting and intense seismic activity of the Middle Miocene. Shockwaves from the earth compacted the sandy sediments and concentrated the limestone cement to mold their spherical lumps.

Bolding by me: This was not AnnK's own comment, rather the quote in her post: To be fair if any where is defined by tectonic activity, New Zealand is going to be very high on a list of countries that spring to mind. However, in my albeit very amateur geological readings, seismic activity has more impact on geography, not on causing incredibly specific, small, localised changes to sedimentary rock structure. There is a lot more physical chemistry going on than a mere tremor or two is going to influence. The impact from 'quakes is going to be far more instrumental, in conjunction with the erosion, of removing these nodules from the surrounding matrix.
No actual mention of 'researchers' field of expertise, or qualifications.


Two locations that I know of in New Zealand have 'spherical' boulders in very localised concentrations. Most famously, Moeraki boulders on the east coast of the South Island, between Dunedin and Oamaru.

https://en.wikipedia.org/wiki/Moeraki_Boulders

The Moeraki Boulders (officially Moeraki Boulders / Kaihinaki) are unusually large spherical boulders lying along a stretch of Koekohe Beach on the wave-cut Otago coast of New Zealand between Moeraki and Hampden. They occur scattered either as isolated or clusters of boulders within a stretch of beach where they have been protected in a scientific reserve. These boulders are grey-colored septarian concretions, which have been exhumed from the mudstone and bedrock enclosing them and concentrated on the beach by coastal erosion.[1][2][3][4]

Underlining by me, think this section is the part worthy of note.

The second location is only a couple of miles downstream from the first photo posted: it is only accessible via the river (public access, if you have watercraft and the skills) or on foot, over private farmland. We knew this location before it was a 'thing', as our farm was opposite the neighbour's, and we camped there occasionally, on agreement. They have since opened it more officially for tourists.

http://www.whitecliffsboulders.co.nz/gallery.html

Google maps grabs: first general location; second, specific location of boulders (within the patch of bush),

Google Street view, looking south into the horse shoe, from which the boulders will have spalled/eroded. Note that the road is on a large terrace, with ~50-60 metre drop to the actual river bed, thus the height seen is obscured by foreground.

Estimated total height of horse-shoe: ~220m from rim to river flat. (Heavy contours 100m, light contours 20m.)

These generally spherical boulders can be seen throughout the region, embedded in the cliff faces along the river, or road cuttings, bulging out like shield bosses. They certainly caused difficulties when farm tracks are cut into the local hillsides by bulldozers, as they are heavier and denser. As a child, I remember my father coming home with half a boulder, about 12-14" across, on the back of the tractor. Exposed and raised from the surface were 3 vertebrae, an inch or so across, one of which was loose. After being a curiosity on the door-step for years, it was taken to a local museum: my memory is obviously hazy (40 years on, and all that), but I seem to recall it was tentatively identified as probable marine vertebrate - anything more would be speculation on my part.


From the Moeraki boulders page, further description of the process is easily found on the linked "septarian concretion", taking you to Wikipedia's "Concretion" page. Of very interesting note, I tried searching 'Trovant' there, and it redirected to this same page...

https://en.wikipedia.org/wiki/Concretion

A concretion is a hard, compact mass formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil.[1] Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin concretio "(act of) compacting, condensing, congealing, uniting", itself from con meaning 'together' and crescere meaning "to grow".[2] Concretions form within layers of sedimentary strata that have already been deposited. They usually form early in the burial history of the sediment, before the rest of the sediment is hardened into rock. This concretionary cement often makes the concretion harder and more resistant to weathering than the host stratum.

There is an important distinction to draw between concretions and nodules. Concretions are formed from mineral precipitation around some kind of nucleus while a nodule is a replacement body.

Descriptions dating from the 18th century attest to the fact that concretions have long been regarded as geological curiosities. Because of the variety of unusual shapes, sizes and compositions, concretions have been interpreted to be dinosaur eggs, animal and plant fossils (called pseudofossils), extraterrestrial debris or human artifacts.

Origins[edit]

Detailed studies have demonstrated that concretions form after sediments are buried but before the sediment is fully lithified during diagenesis.[3][4][5][6][7][8] They typically form when a mineral precipitates and cements sediment around a nucleus, which is often organic, such as a leaf, tooth, piece of shell or fossil. For this reason, fossil collectors commonly break open concretions in their search for fossil animal and plant specimens.[9] Some of the most unusual concretion nuclei are World War II military shells, bombs, and shrapnel, which are found inside siderite concretions found in an English coastal salt marsh.[10]

Depending on the environmental conditions present at the time of their formation, concretions can be created by either concentric or pervasive growth.[11][12] In concentric growth, the concretion grows as successive layers of mineral precipitate around a central core. This process results in roughly spherical concretions that grow with time. In the case of pervasive growth, cementation of the host sediments, by infilling of its pore space by precipitated minerals, occurs simultaneously throughout the volume of the area, which in time becomes a concretion. Concretions are often exposed at the surface by subsequent erosion that removes the weaker, uncemented material.

Apologies for the local information overkill! Couldn't help myself, when it seems somewhat pertinent to the subject, and a walk-down memory lane: I'm viewing the google images from Scotland, 25 years gone from home....


All in all, if locals were of a more 'poetic' bent, of course these were devils marbles, or dragon's eyeballs, or just simply 'grow' from fresh air and rain-water...

 

[Ann K]

Apologies for the local information overkill! Couldn't help myself, when it seems somewhat pertinent to the subject, and a walk-down memory lane: I'm viewing the google images from Scotland, 25 years gone from home....

More local information:
I'm many years gone from my native Scotland, but grew up in Ohio. I wish I'd seen concretions the size of these! My family knew a nearby farmer on whose property we found many smaller concretions in a stream bed, mostly broken bits. But my best friend lived on a farm where a concretion of about 15 inches in diameter was cemented into place as a driveway marker. Her dad had hauled it there with the tractor many years before.

My parents and my in-laws sometimes went fossil-hunting in the area of Brown county, Indiana, and brought back both geodes and many concretions which held leaf fossils. I was sitting outside my back door cracking some open, when my neighbor came over, asking (in Polish) "Oysters?"

 

[Ann K]

However, in my albeit very amateur geological readings, seismic activity has more impact on geography, not on causing incredibly specific, small, localised changes to sedimentary rock structure.

Seismic activity is, however, a local phenomenon, as is the formation of concretions. I have no idea if I'm interpreting it correctly, but (my interpretation) it seems possible to me that seismic activity could cause small fractures in some already-existing concretions in an area. Those cracks are necessary to form septarian concretions, where the crack is later filled with deposited minerals. Sometimes the round ones are found mixed with the septarians, and the mineral composition is the same for them both.

 

[psikiwi]

I have no idea if I'm interpreting it correctly, but (my interpretation) it seems possible to me that seismic activity could cause small fractures in some already-existing concretions in an area. Those cracks are necessary to form septarian concretions, where the crack is later filled with deposited minerals.

I think there is some 'interpretation' required, but the original quote was

Researchers have found no difference between the Trovants and the surrounding sand substrate. So they suspect the spheroid shapes were formed by the unusually long-lasting and intense seismic activity of the Middle Miocene. Shockwaves from the earth compacted the sandy sediments and concentrated the limestone cement to mold their spherical lumps.

Bolding mine.

I agree 'quakes may well split already formed concretions, but I would need to do a lot more reading to discover how seismology causes them.