Metamorphic:

It’s over thirty years in the future and one of Mensah’s grandchildren is chatting away to her as they do some gardening together. They find an interesting rock and Mensah suggests the child puts it to one side and asks uncle Gurathin (or great uncle Gurathin) about it later.

And the child says “Or SecUnit?” And then does that thing little children do and asks why SecUnit and Gurathin aren’t married if they live together. And Mensah explains that not everyone who lives together is married, and that some people just live together.

“But why aren’t they married?”

And Mensah senses this is something that’s been bothering the child, so she stops pulling up the roots of weeds and looks at the child, who is now drawing in the dust with a stick.

“Well, people get married because they love each other.”

Child stabs at a hole in the ground with the stick.

“Devi and Stannal are married, and they don’t seem to even *like* each other, they mostly shout at each other.”

Mensah laughs, those two members of her extended clan do seem to have a relationship which stretches the meaning of the word volatile.

“They sometimes don’t show it, but they do love each other very much.”

“But, Uncle Gurathin and SecUnit? Don’t they?”

The words “love each other” hang in the air.

Mensah pauses to think. She supposes the obvious answer is “No, not like that.”

But that’s a stupid answer. As if they can’t “love” (she mentally inserts the inverted commas around the word, like little tongs holding something slightly distasteful: only because just thinking of applying the word to SecUnit conjures up an image of its face hearing her do so) each other because they don’t have any sort of physical relationship? Because they would never even hug? Mensah has seen them occasionally touch each other, but it’s been almost forty years now, and she could probably count the times (if you discount those which involved one of them being close to death) on her fingers. The occasional hand laid on a shoulder; she was sure everyone noticed and tried very hard not to be seen to notice.

She wondered if they laughed about the way other people responded to them, together on the feed.

“Why don’t they live on Perihelion anymore?”

Oh, so the thoughts had moved on.

“Well, uncle Gurathin is getting quite old now” we all are, she thought, “and artificial gravity and space travel are easier when you’re young. He prefers to stay on the planet now.”

The hole in the ground was being enlarged, the stick twisted.

“SecUnit says it doesn’t like the planet.”

Mensah sighed.

“But it says it like it’s a joke. It says it doesn’t like uncle Gurathin either sometimes too. I’ve heard it.”

Someone had obviously been paying attention.

“Do you think it likes the planet?”

“It take me on long walks and shows me plants and rocks and animals. It can recognise all the bird songs. There are wild birds that come to it when it calls.”

Yes, Mensah thought. Whether SecUnit liked the planet or not, it certainly seemed to like it. The fields surrounding Gurathin’s farm were beautifully tended, though the garden a wilderness it was an intentional wilderness. It probably took a lot of work to keep it that way, a haven for wildlife but aesthetically pleasing too.

The stick was drawing circles in the dirt again now.

“But they aren’t married?”

No they aren’t, Mensah wonders if SecUnit would even be outraged at the suggestion anymore. Probably not. Gurathin would still almost certainly act mock horrified.

“Do you know how long ago the first construct/human marriage here on Presevation was?”

Child now looks up, wide eyed.

“It must be ages and ages ago. Three has been married forever!”

“It was not that long before you were born. Before then it was illegal here like everywhere else.”

The child looks a bit sad, “But they must have loved each other before then?”

Mensah isn’t sure if this is a specific “they” or a more general comment on how Preservation customs and laws had responded to the influx of “free constructs” over the last few decades.

“Sometimes people are slow to change.” She says, hoping this covers the child’s actual question.

“Well I think they should get married.”

Mensah looks at the vegetable bed, she reckons they’ve done enough for today.

“Well, you can tell them that when you ask about the rock. Let me know what they say.”

Later the child tells her that it’s a piece of blueschist, and it’s a type of metamorphic rock. It’s been described by geologists as the prettiest rock there is, formed in high pressure low temperature situations like cold oceanic slab subducts.

So Mensah is glad that’s been cleared up.

okay but hear me out, metamorphic rocks — schist edition

The incredible textures of metamorphic rocks under the microscope

Rocks are beautiful part 6/?

Source: Bernardo Cesare (micROCKscopica)

Needles of sillimanite in cordierite

Euhedral garnet in biotite gneiss

Muscovite and quartz in phyllite - Eastern Alps

Albite-rich layer in graphitic schist - Eastern Alps, Italy

Crenulation of mica-rich layers in phyllite - Eastern Alps, Italy

Blueschist - Aosta Valley, Italy

Myrmekite (wormy intergrowth of quartz and plagioclase) in a metapelitic granulite - Antarctica

The Franciscan Formation

The geology in California today is a consequence of hundreds of millions of years of interaction between a continent and oceanic plates. One of the most widespread consequences of that interaction found today are the rocks you see here, the rocks cities like San Francisco are built on; the Franciscan formation.

The story of the Franciscan formation starts over 500 million years ago when a piece of North America rifted away from what is today California. An ocean basin, like that found today off of the East coast of the U.S., formed. Sediments piled up on this plate; worn down pieces of North America, washed to the ocean by rivers.

When oceanic plates get a couple hundred million years old, they get cold and they get dense. They get so dense that they start sinking into the mantle; they start to subduct. Sometime in the Jurassic period, the oceanic crust off California started subducting.

When oceanic plates subduct, the oceanic crust sinks into the mantle, and the pile of sediments on top has to go somewhere. The density of the oceanic crust is what drives subduction, but the sediments aren’t nearly as dense so they don’t go down easily. Whether they go down depends on whether the oceanic plate is dense enough to drag them down with it.

At a subduction zone like the one in California, the dense oceanic plate subducts beneath the continental plate, and the continental plate can work just like a rubber kitchen scraper. Any rocks sitting loosely on the oceanic plate can be scraped off into a giant pile at the edge of the continental plate.

These scraped-off rocks form a thick, wedge shaped, faulted pile with a tip towards the subduction zone. This shape is called an accretionary wedge or an accretionary prism.

The rocks that make up an accretionary wedge have a pretty rough life, all things considered. They’re scraped off of the oceanic plate, faulted and fractured, but the subduction zone keeps trying to drag them downwards.

This creates a unique situation. These rocks are dragged to high pressures in the upper portion of the mantle, but they’re also colder than the other rocks at that depth because they were sitting at the surface and haven’t been heated very much. This set of conditions is appropriate for a certain type of metamorphism that creates a rock known as a “blueschist”.

Some blueschist rocks are actually blue because of specific minerals, but not all of them, including the rocks you’re looking at here. The rocks of the Franciscan formation are mostly blueschists even though they’re not all blue.

Between about 200 million years ago and 30 million years ago, the Farallon plate subducted beneath California. As that happened, a mixture of sediments sitting on that plate and the occasional broken piece of the Farallon plate were scraped off by the North American plate, forming a thick accretionary wedge. Many of those sediments were pushed to high pressures, causing metamorphism and the growth of new minerals.

The subduction zone wiped out the rocks that made up the crust of California beforehand. Since subduction stopped, the rocks that made up the accretionary wedge have been broken up and moved by new faults; most notably the San Andreas.

The Franciscan Formation is this subduction complex. Much of California outboard of the Sierra Nevada is made up of rocks like these, scraped off of the Farallon plate and smashed together by the forces of subduction.

-JBB

agardite, mixite and blueschist’s permafusion 

her powers include: summoning anything she wants (doenst work for magical itens), minor hydrokinesis, and she’s a heck of a good singer