Icon from a picrew by grgikau. Call me Tir or Julian. 37. He/They. Queer. Twitter: @tirlaeyn. ao3: tirlaeyn. 18+ Only. Star Trek. Sandman. IwtV. OMFD. Definitionless in this Strict Atmosphere.
Dun Briste and the surrounding cliffs were formed around 350 million years ago (during the ‘Lower Carboniferous Period’), when sea temperatures were much higher and the coastline at a greater distance away.
As a fun little addition, look about a third of the way up, where the clean horizontal lines of the outcrop are broken by a small arc, thick in the middle and pinching out towards the sides, concave upwards and with a darker/black color.
That’s a fluvial deposit, probably a small creek or river- the arc is a cross section, so the lowest point is the deepest part of the river. It’s darker because it was rich in organic matter, and after the plant matter was buried here the constituent carbon remained for millions of years- possibly as a small lignite or coal deposit. (‘Carboniferous’ period, right? It’s a common sight in this age of rock)
This is a 350,000,000 year old riverbed. Fun to imagine standing by that ancient creek, ferns and primitive moss growing thick in the shallows, insects and the odd critter enjoying themselves on the banks, and knowing that something of this moment would remain even three hundred and fifty millions years in the future, embedded in a monolith rising above the sea.
The Munsell Soil Color Chart is a 9 page reference binder, distinguishing between more than 300 naturally occurring soil colors.
Often the contrast is subtle, or on such a big scale you can’t really appreciate it, or the color bands are layered and hidden underground.
However, Vinicunca, the Rainbow Mountain in Peru, has many vibrant dirt colors in dramatic stripes!
See also the Zhangye Danxia landforms in China, or the Paria River Canyon in Utah, or various natural mineral deposits if you aren’t too pedantic about what you call “dirt”
Hormuz Island in Iran has a lot of cool things going for it, including rainbow caves and iridescent layered sand!
I’m trying to add photos on Tumblr Mobile and it is misbehaving in frustrating ways, but rest assured there is cool geology out there
hey want to see something gorgeous but viscerally discomfiting?
No <3
okey doke!
The Mauritius “underwater waterfall” is not a true waterfall but an naturally occurring optical! In the sense that that’s not water falling, it’s sand and silt shifting! Shifting down a 4000-meter-deep abyssal drop. It is in fact exactly as deep as it looks, sorry :)
man the Appalachian mountains really aren’t shit huh
The Rockies are new, young and virile and fresh from the Laramide orogeny, tall and lanky teenagers on the geological scale.
the Appalachian mountains are old, formed hundreds of millions of years ago before dinosaurs walked the Earth. They are ancients, elders, witnesses to half a billion years of life coming and going.
To be tall is not a virtue. To be small is not a sin. The Appalachians are eroding under the weight of time, slowly shrinking and returning to the Earth from which they sprang.
Appreciate them while they are still here.
I do want to say real quick again about the age of the Appalachians…
They said “before dinosaurs,” but we have a cave here that began forming between 450 million to 550 million years ago.
There are no bones in that cave. No fossils. No nothing.
That’s because this cave began forming before bones existed on land, and had only just started to exist in the ocean. Shellfish hadn’t evolved yet. Limestone, which forms many caves, was just starting to become a more prevalent rock.
The mountains aren’t older than dinosaurs. They are older thanbones.
see that little lump up at the top of minnesota? the sawtooth mountains? so small most places would just call them hills?
those are over a billion years old.
that’s why they’re so small. they’re the last ancient remnants of a lava flow 5 miles thick. the lava didn’t kill any dinosaurs. or any fish. or any animals at all. because there were no animals. you know what there was?
algae.
those mountains were 5 miles tall when the most advanced life on earth was algae.
so i’m just gonna go ahead and keep calling them mountains, even though all you need to climb them is hiking shoes and a nice afternoon. because a place where you can crouch down and touch basalt that was lava before leaves were invented deserves some respect.
The earth is unfathomably ancient, and you garner no love from her when you insult her eldest children.
striped icebergs form as meltwater refreezes in crevasses atop glaciers before air bubbles can become trapped in the ice, which is later calved into icebergs, or when supercooled seawater freezes inside cracks beneath an ice shelf, which then becomes visible when the iceberg breaks off and flips.
over time, the weight of accumulated snow contorts and curves these blue bands of ice, as does erosion from waves and wind. dust and volcanic ash falling on the iceberg can darken the ice, while dissolved organic compounds entering from below can shade it towards cyan.
accumulated snow also compresses air bubbles trapped in the iceberg, thus preventing them from otherwise interfering with the passage of light. and because water absorbs photons from the red end of the visible spectrum much better than the blue end, bubble free ice takes on a blue colour.
(click pic or link for credit x, x, x, x, x, x, x, x)
Postpiles like this occur when large pools of basalt cool under a glacier. The lava freezes on all 6 sides, and then slowly cools on the interior. But because it shrinks as it solidifies (unlike water), that puts the interior under tremendous internal stresses, which tend to break along hexagons (with occasional pentagons and septagons thrown in) because that’s a shape that tesselates while also minimizing perimeter to area ratio (ie the least amount of high-energy cracking needed per volume). And then at some point something weathers the top and sides so you can see it. And yes they are this cool in person.
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This formation is close to a glacier. Not sure which one, but you can tell from the telltale blue-green water, which indicates a high concentration of the type of superfine sediment that you get in glacial runoff. And that is also amazing to see in person (water is actually fairly rarely really blue).
Thanks for the explanation! Giant’s Causeway in Northern Ireland/Southern Scotland is another example.
