How was Earth flat in Grenvillean?

[snorkack]

It is recently claimed that between 1800 and 800 million years ago, Earth was flat. This is supposedly indicated by lack of minerals that should have formed in mountains´ roots.
However, from that period, there are rocks formed in orogeny - mountain forming processes. For example Grenvillean orogeny in North America 1200 to 1000 million years ago, Sveconorwegian orogeny 1140 to 960 million years ago, and Kibaran orogeny 1400 to 1000 million years ago.

Given the Grenvillean etc. orogeny, how come Earth was flat?

 

[Rive]

It is recently claimed that between 1800 and 800 million years ago, Earth was flat.

Interesting news. Could you please give us a link to that claim?

 

[DrClaude]

Could you clarify what you mean by flat?

 

[snorkack]

Is pubs.acs.org a good source for you? Referring to Science?
https://pubs.acs.org/doi/full/10.1021/cen-09906-scicon11
Headline, as from pubs.acs.org:
Europium reveals time when Earth was flat
What they mean is absence of mountains, as shown by absence of minerals characteristic to mountain roots.
My question is, since geological record of the period does show formation of mountains in that time, such as Grenvillean and Sveconorwegian, how is that consistent with Earth being flat?

 

[BWV]

But just looking at the abstract, it indicates fewer mountains - the flat in the title seems to be a bit of hyperbole. The various ‘Snowball Earth’ periods during the Proterozoic have been attributed in part to much lower level of tectonic activity. There are a few surviving mountain ranges that predate the period - the Laurentine Shield for example

 

[Oldman too]

The words Flat and Earth included in the same sentence here always gets my attention. This is rare, a contextual issue that let the thread live through a discussion, nice. Obviously the term "Boring Billion" could be misconstrued as "Flat" in the sense of topologically profile, however when the Term "B.B." is referred to in it's other popular term "Barren Billion" we have to rethink the context.
The term seems to apply more correctly to the biological evolution than the geologic evolution... although plate tectonics and overall related features do seem to be suppressed during the same period.
A quick read on the Bio vs. Geo opinion (of course, the "opinion" part is a disclaimer)
https://www.nature.com/articles/s41598-018-22695-x

 

[snorkack]

https://www.nature.com/articles/s41598-018-22695-x

Absence of banded iron formations, evaporites, phosphorites, glaciation events and major ore deposits related to convergent plate margins (Orogenic Au, porphyry, VHMS and MVT deposits) also correlate with the period of stasis

Suggesting Earth being flat.
And yet rocks exist from the period, connected to orogeny - mountain formation.
Besides the ones I listed above, also Yavapai province, Mazatzal province, Picuric orogeny...
How is the existence of orogenic rocks from the period consistent with Earth having been flat then?

 

[Astronuc]

Putting some time on the orogeny periods/episodes:

Yavapai orogeny 1710–1680 Mya
Mazatzal orogeny at 1650–1600 Mya
Picuris orogeny at 1450–1300 Mya
https://en.wikipedia.org/wiki/Picuris_orogeny (at least a couple of typos on dates in this article)
Cites: https://pubs.geoscienceworld.org/gs...nic-model-for-the-Proterozoic-growth-of-North
Grenville orogeny at 1300–950 Mya
https://en.wikipedia.org/wiki/Grenville_orogeny (or 1250–980 Ma)
Sveconorwegian orogeny 1140 to 960 million years ago
https://en.wikipedia.org/wiki/Sveconorwegian_orogeny

Ostensibly, whatever 'mountains' formed eroded relatively quickly. I wonder what the climate/weather was like during those periods and how it varied between summer and winter.

Bear in mind that what became the continents today were probably thousands of miles away from present positions. According to some simulations, there was very little, if any, dry land in the norther hemisphere, and as I recall, oceans/seas were relatively shallow.

Plate tectonic evolution from 1 Billion years ago to the present.

from - https://singularityhub.com/2021/02/...illion-year-dance-of-Earth's-tectonic-plates/
Andrew S. Merdith, Simon E.Williams, Alan S.Collins, Michael G.Tetley, Jacob A.Mulder, Morgan L. Blades, Alexander Young, Sheree E. Armistead, John Cannon, Sabin Zahirovic, R. Dietmar Müller, "Extending full-plate tectonic models into deep time: Linking the Neoproterozoic and the Phanerozoic," Earth-Science Reviews Volume 214, March 2021, 103477
https://www.sciencedirect.com/science/article/pii/S0012825220305237

Animation of plate tectonics 540 Ma to present

https://www.earth.northwestern.edu/our-people/affiliated-faculty/scotese-christopher.html

Consider - https://www.sciencedirect.com/science/article/pii/S0024493720305259
R. Tamblyn, D. Brown, M. Hand, L. Morrissey, C. Clark, R. Anczkiewicz
"The 2 Ga eclogites of Central Tanzania: Directly linking age and metamorphism," Lithos
Volumes 380–381, January 2021, 105890
https://en.wikipedia.org/wiki/Eclogite

Also, note that geological situation in what is now Gabon, Africa about 1.7 billion years ago (sandstone over granite).
https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor

A key factor that made the reaction possible was that, at the time the reactor went critical 1.7 billion years ago, the fissile isotope ²³⁵U made up about 3.1% of the natural uranium, which is comparable to the amount used in some of today's reactors. (The remaining 96.9% was non-fissile ²³⁸U.) Because ²³⁵U has a shorter half-life than ²³⁸U, and thus decays more rapidly, the current abundance of ²³⁵U in natural uranium is about 0.70–0.72%.

Note that europium is a fission product (more so from fast fission) as well as a transmutation (n-capture) of samarium (also a fission product). About 800 million years ago, the enrichment of natural U would have been reduced to something like 1.4 to 1.5% from about 3.1% (it might have been 3.3-3.4% at 1.7 billion years).

I'd be interested to learn the origin of the zircon specimens. In another paper, it mention zircons from Tibet.