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Tom Mazanec
2017-Dec-21, 02:43 PM
If a lava flow enters water, like a lake or river, can it form a beach of solid glass? Normally I would not expect that (I'd think the "glass" would shatter into particles), but I'd even less expect a natural reactor, and that happened once.
If it is possible, is one actually known?

Squink
2017-Dec-21, 03:55 PM
Obsidian beach (https://www.explore-the-big-island.com/black-sand-beach.html):
Punalu’u Black Sand Beach is one of the finest examples of a true black sands beach anywhere in the world. The obsidian-black sand at Punalu'u is truly a sight to behold.
Sea glass beaches (https://www.odysseyseaglass.com/sea-glass-british-isles.html) (bits of bottles)

CJSF
2017-Dec-21, 05:48 PM
Did you mean glass "grains" - like what Squink has linked to - or a solid "flow" of smooth glass along a stretch of shore, as your "shattering" expectation implies?

CJSF

Trebuchet
2017-Dec-21, 06:21 PM
A lava flow entering water is going to suffer too much thermal shock to remain as a smooth sheet, I think.

grapes
2017-Dec-21, 06:27 PM
I don't see why an obsidian outcrop couldn't be a beach, though.

Tom Mazanec
2017-Dec-21, 10:16 PM
Yeah, I was thinking a sheet (if I understand what the SF book was describing).

CJSF
2017-Dec-21, 10:25 PM
I can think of several plausible ways that such a "beach" might form (I'd say it's more of a shoreline, but geoscience semantics, right?), but most volcanic glass that I know of would be quite brittle, even if it was thick. It'd have to be some fairly gentle surf or a very new "beach".

CJSF

DaveC426913
2017-Dec-22, 01:26 AM
Yeah, if it were solid, it wouldn't be a beach. It would be a shoreline - solid right to the water. And I'm pretty sure there are paces where you could walk on a cooled lava flow right to the water's edge.

But even at that, it would not be flat. Lava is far too viscous to flow like water. You'll get a lumpy, craggy, rolling surface.

eburacum45
2017-Dec-24, 09:41 AM
Yeah, I was thinking a sheet (if I understand what the SF book was describing).
Since a natural glass beach is unlikely, I would guess that the author was implying or hinting at the possibility that this glass beach formed as the result of activity by an intelligent species in the past. A powerful laser or some other beam weapon, or a nuclear/antimatter airburst bomb could fuse the sand of a normal beach into glass. A natural meteoric impact might do it too, although I can't think of any real life examples.

The name for glass formed by high-energy weapon events is Trinitite
https://en.wikipedia.org/wiki/Trinitite

The glass has been described as "a layer 1 to 2 centimeters thick, with the upper surface marked by a very thin sprinkling of dust which fell upon it while it was still molten. At the bottom is a thicker film of partially fused material, which grades into the soil from which it was derived. The color of the glass is a pale bottle green, and the material is extremely vesicular with the size of the bubbles ranging to nearly the full thickness of the specimen."

KaiYeves
2017-Dec-24, 08:27 PM
Since a natural glass beach is unlikely, I would guess that the author was implying or hinting at the possibility that this glass beach formed as the result of activity by an intelligent species in the past. A powerful laser or some other beam weapon, or a nuclear/antimatter airburst bomb could fuse the sand of a normal beach into glass. A natural meteoric impact might do it too, although I can't think of any real life examples.

The name for glass formed by high-energy weapon events is Trinitite
https://en.wikipedia.org/wiki/Trinitite
I don't know about a whole beach, but aren't tektites normal ground turned to glass-like stone by meteor impacts?

eburacum45
2017-Dec-24, 10:31 PM
Tektites are glassy ejecta, rather than a layer of glass formed in situ by radiated heat. But the basic cause is the same.

SkepticJ
2017-Dec-24, 11:39 PM
The name for glass formed by high-energy weapon events is Trinitite
https://en.wikipedia.org/wiki/Trinitite

"Nuke the beach from orbit, it's the only way to be sure."

KaiYeves
2017-Dec-25, 01:25 AM
Tektites are glassy ejecta, rather than a layer of glass formed in situ by radiated heat. But the basic cause is the same.

Yes, that's what I meant. They're little bits of ground, not a whole solid surface.

Tom Mazanec
2017-Dec-25, 08:31 PM
Here is where I got it from
https://gailearth.com/about-2/life-on-the-planets/wyzdom/account-of-life-on-wyzdom/#3.3.002

Squink
2017-Dec-25, 11:33 PM
The things I love most about a glass beach is its slippery when wet smoothness, and the possibility of unspeakably sharp edges where a chunk of granite bashes up on it a little too hard to make a perfectly conchoidal fracture.
On this planet, you might get a solid chunk of glass at the seashore by geologic tilting and lowering of a pre-existing Obsidian layer. A timely earthquake or landslide might expose pristine glass right at the shoreline.

chornedsnorkack
2017-Dec-26, 11:18 AM
Glass tends to be brittle compared to crystalline rock because the glass easily propagates cracks, where grain boundaries in polycrystalline aggregate could stop cracks.

Thermal shattering would be caused by stresses due to thermal expansion.

Therefore a melt with low thermal expansion would still be brittle on mechanic blows, but would be less prone to shatter on cooling.

Which glasses might have low expansion?

BigDon
2017-Dec-29, 12:58 AM
Pyrex glasses for one.

I recall reading that on Earth in the pre-Cambrian magma was much hotter, by some 300C, and basalt flows had the viscosity of water! They would leave flows a quarter of an inch high. I believe examples can be found in select locations in Canada.

danscope
2017-Dec-29, 04:07 AM
Well, you know why glass blowers go through the trouble of building and running an annealing oven
and having a long, steady cool down of molten glass. Otherwise it breaks up pretty easily into particles.
And yes...."Pyrex" is different.

trinitree88
2018-May-09, 03:45 PM
Tom. You could of course find a nice sandy beach. Mark it with a big "X" on a map, with GPS coordinates. Call the Air Force from the Oval Office, if you reside there. Request a special airmail delivery. Voila! Beach with glassy surface, instead of desert.....custom made. The green stuff might glow in the dark a bit, instead of natural bioluminescent critters.
SEE:https://www.atlasobscura.com/articles/object-of-intrigue-green-glass-created-by-an-atomic-bomb


SEE:https://www.hscott.net/analyzing-trinitite-a-radioactive-piece-of-nuclear-history/



pete

Eclogite
2018-May-09, 07:03 PM
I recall reading that on Earth in the pre-Cambrian magma was much hotter, by some 300C, and basalt flows had the viscosity of water! They would leave flows a quarter of an inch high. I believe examples can be found in select locations in Canada.Some pre-Cambrian magmas, but not basalts, komatiites (https://en.wikipedia.org/wiki/Komatiite). This paper (http://www.itg.cam.ac.uk/people/heh/Paper66.pdf) has a detailed section on komatiitte rheology.

BigDon
2018-May-09, 07:49 PM
Thanks for the clarifying link Eco, but I was just repeating what I had read.

"If I told you a lie, I was just passing one along."

Is an old, often true Navy phrase. :)

Eclogite
2018-May-10, 08:06 PM
Thanks for the clarifying link Eco, but I was just repeating what I had read.

"If I told you a lie, I was just passing one along."

Is an old, often true Navy phrase. :)One gets few opportunities to mention komatiites, so when I see one I grab it. :)