continental crust

Most people (perhaps I’m being a little optimistic, but hey) these days are familiar with basic tectonics and have a vague notion of what Pangaea is. The thing is, Pangaea existed only around 225 million years ago, but the history of Earth goes well over 4 billion years before that. So, aren’t you curious as to what on earth (quite literally) was going on for all that time?

It is estimated by geologists that the first continental crust formed about 4 billion years ago (now referred to as bya because I’m lazy), near the end of something called the Hadean eon (4.5-3.8 bya). By 3.7 bya there was a substantial amount land but still less than 10% of what we have today. Amazingly, some of the rocks that were formed during this period are still present today. Relics of this time (and later) are known as cratons, there are plenty of them around but some of the most spectacular are in Canada where there are tonalite rocks dating 4.0 bya and in Greenland where they’re just behind and 3.85 bya.

Ok, so we have our first bits of land, and of course during this time the Earth’s tectonic plates still moved, subducted and created crust in the same way they do today. By 3.6 bya this lead to the formation of the first supercontinent, Vaalbara, so named for the cratons that composed it. It was made up of two separate cratons which now reside in southern Africa (Kaapvaal) and western Australia (Pilbara). No, I don’t know who decided to call them that. We can tell they used to be together because of the incredibly similar lithological and paleomagnetic structures and sequences in both areas, which have obviously been carbon dated to around this time.

Again through tectonic movements, Vaalbara begins to separate at around 2.8 bya. The continental crust continues to grow in size until 2.7 bya when the cratons come together as another super continent with another silly name - Kenorland. Are you beginning to see a pattern here? It’s called the supercontinent cycle and basically is the quasi-periodic coming together and dispersal of the Earth’s continental crust. This process is inevitable given that the Earth is a sphere and the plates are constantly in motion - there is going to be a collision at some point. When they do collide, the immense force and pressure at some point creates a new plate boundary which forces them away from each other again. This happens over and over again and the continents are constantly reconfiguring themselves.

Anyway, back to the story. Kenorland breaks up around 2.1 bya and by this point there are quite a few significant land masses floating around, and by significant I mean continents in their own right, not just tiny cratons. There’s Ur (3.0 bya), Atlantica (2.0 bya) and Nena (1.8 bya). During the formation of Nena, from a previous continent Artica, in 1.8bya the continents came together again as Columbia, almost certainly named after it’s squeaky tap-dancing counterpart in the Rocky Horror Picture Show. Columbia further developed by 1.5 bya into the biggest continent, yet Rodinia and is probably the best known supercontinent other than Pangaea.

It is important to remember at this point there is absolutely no life on land as the Earth's atmosphere is far too hostile and there is basically no oxygen for organisms to survive. There is however a rapidly growing plethora of species in the oceans, even multicellular organisms and primitive invertebrates. These have been evolving since around 3.5 bya first as single cellular organisms and eventually to eukaryotes and then invertebrates. It was only after the break up of Rodinia around 750 million years ago (mya) and huge global cooling that the rapid evolution of primitive life forms began start at the beginning of the Cambrian period.

After the break up for Rodinia the continents came back together fairly quickly in 600 mya as Pannotia, which was basically the same landmass but just organised in a different way. Again, it breaks up only around 100 million (500 mya) years later into Gondwana and a handful of other continents which will eventually become Laurasia. The continental pieces continue to float around coming closer and closer to what we know as Pangaea. By now it is the Silurian (420 mya) period and algae and bacteria and altered the atmosphere, mainly in the Ordovician period enough for life to start developing on land. Hooray!

Finally, 300 million years ago Pangaea begins to come together.  By 225 mya it is a fully formed super continent and it is the dawn of the Age of the Dinosaurs in the Triassic era. Life has come a long way in since the Silurian…they grow up so fast. The rest, as they say, is history. Of course, I could, and would love to, go into detail on the rest of it but I think I’ll save that for another piece. This was intended as a brief history of Earth and life before Pangaea only. Hope you enjoyed this :3

Mineral Mondays: Quartz

Natural History:

Quartz is a clear or white form of silicone dioxide found all around the world, and is the second most common mineral found in the Earth’s continental crust. Quartz is often found embedded in sedimentary rocks, including sandstone and shale and as part of igneous rocks, like granite.

History & Folklore:

Roman philosopher Pliny the Elder believed quartz to be ice, permanently frozen after very long exposure to freezing temperatures.

Also called the Witch’s mirror or the Star Stone

Hercules dropped the Crystal of Truth from Mount Olympus, shattering it into all the pieces we find today. Since clear crystals come from the Crystal of Truth, it is said that anyone using a clear crystal while divining can never lie.

In parts of Asia, crystal is thought to be pure dragon essence

Associations:

Angel: Michael
Gods/Goddesses: The Great Mother, Daramulun, the Great Rainbow Snake, Hecate, Yemaya, Olokun, Klehanoi
Chakra: Crown
Element: Water, fire
Astrological Sign: Cancer, Leo

Uses: 

Body: Boosts the immune system. Clears negative debris causing disease from the aura. Relieves pain and fevers. Relieves vertigo. Aids healing and tissue regeneration.

Mind: Fuels memory. Aids concentration. Gives creative insight. Balances emotions.

Magick: Facilitates clairvoyance and divinatory abilities, aids in mediation, induces prophetic dreams, protects against psychic attack, purifies aura and soul.

Care:

Cleanse frequently by smoke cleansing or in sunlight, or saltwater. If you wish to use a singing bowl, use the bowl near it. Do not put the stone in the bowl as the vibrations against the bowl may damage the points. Recharge under a plant under either the sun or the moon.
In terms of the nonlinear dynamics of our planet, the thin rocky crust on which we live and which we call our land and home is perhaps the earth’s least important component. The crust is, indeed, a mere hardening within the greater system of underground lava flows which, organizing themselves into large “conveyor belts” (convective cells), are the main factor in the genesis of the most salient and apparently durable structures of the crusty surface. Either directly, via volcanic activity, or indirectly, by forcing continental plates to collide, thereby creating the great folded mountain ranges, it is the self-organized activity of lava flows that is at the origin of many geological forms. If we consider that the oceanic crust on which the continents are embedded is constantly being created and destroyed (by solidification and remelting) and that even continental crust is under constant erosion so that its materials are recycled into the ocean, the rocks and mountains that define the most stable and durable traits of our reality would merely represent a local slowing down of this flowing reality. It is almost as if every part of the mineral world could be defined simply by specifying its chemical composition and its speed of flow: very slow for rocks, faster for lava.

Similarly, our individual bodies and minds are mere coagulations or declarations in the flows of biomass, genes, memes, and norms. Here, too, we might be defined both by the materials we are temporarily binding or chaining to our organic bodies and cultural minds and by the timescale of the binding operation. Over the millennia, it is the flow of biomass through food webs, as well as the flow of genes through generations, that matters, not the bodies and species that emerge from these flows. Our languages may also be seen over time as momentary slowing downs or thickenings in a flow of norms that gives rise to a multitude of different structures. And a similar point applies to our institutions, which may also be considered transitory hardenings in the flows of money, routines, and prestige, and, if they have acquired a permanent building to house them, in the mineral flows from which the construction materials derive.
—  Manuel De Landa

[06/26/2016] The geology of Palawan is, in many ways, unlike other parts of the Philippines. The crust of northeast Palawan was derived from the southeast edge of the continental crust of China, part of the Eurasian Plate. It is the exposed portion of a microcontinent that drifted southward with the opening of the South China Sea. (Sabang, Palawan, Philippines)

So a few people asked me to expand on my post where I was asked if I tie my deities with science in any way. Since someone else asked me to ramble on Jorm, I figure I’ll start with zir.

I see Jormungandr in the cycle of crust creation and subduction as well as in Earth’s magnetic field. Jorm is an ouroboros - a symbol of self reflexivity and self-creation in the form of a serpent or dragon biting its own tail. At its end it begins again and its end feeds into itself. The way our crust is made is much the same. Magma bubbles up at rift zones in the ocean, cooling and forming rock. Further rifting continues to push the crust apart. At its far edges, cooled oceanic crust is dense and sinks beneath lighter continental crust. The old crust subducts and eventually begins to partially melt, creating the magma that will eventually bubble up again. Its end leads to and fuels its rebirth just like with Jormungandr. 

The production of Earth’s magnetic field is due to the structure of our core: the liquid outer core and the solid inner core. Because of temperature differences, the liquid out core moves and produces convection layers in accordance with the Coriolis Effect. In addition, the flowing iron produces electrical currents which create a magnetic field. The planet’s magnetic field is one of the Earth’s most potent defenses. It protects us from harmful radiation by shielding our atmosphere from solar winds. If we didn’t have it, our atmosphere would be akin to Mars’s. As the magnetic field wraps around Earth, Jormungandr encircles Midgard. Some believe zir to be a protective ring of sorts, which to me, strongly correlates to Earth’s magnetic field. In addition, the process of crust production is linked to this as a good portion of plate tectonic shifting is due to the dynamics of the inner-outer core producing heat to melt the bottom of the mantle which then convects heat upwards, allowing for the mantle to flow in the solid state. Jorm is about flow, creating anew from the destruction of the self, and a protective force and I very much see zir in these processes and phenomena.

The Flights as Common Rocks


Light = Conglomerate

What could possibly be more appropriate than a monstrous re-formed (sedimentary) rock made of the leftover bits and pieces of other rocks, right? Those original rocks were probably buried too close together. 
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Lightning = Slag

A glassy artificial rock - a waste product of separating a mineral from its ore. A sure sign of technological and industrial progress! 
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Fire = Scoria

This quickly-cooled igneous rock is often referred to as “Lava Rock” 

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Arcane = Banded Iron Formation

The conditions under which this sedimentary rock formed no longer exist anywhere on Earth, and to our knowledge, may not ever exist on Earth again. Plus the iron bands seem to shimmer at the right angle, that’s… almost like magic. 

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Plague = Quartzite

This metamorphic rock is extremely resistant to weathering - it is resilient and lasting.  

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Earth = Granite

This igneous rock makes up most of Earth’s continental crust. 

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Ice = Chalk

This sedimentary rock certainly looks like a tiny replica of snow if you powder it up. 
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Shadow = Gabbro

This dark coarse-grained igneous rock was created unseen deep, deep underground (in the crust under the ocean, most likely). 
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Wind = Sandstone

This sedimentary stone is what makes up the famous Windswept Rocks
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Water = Pegmatite

While its composition is the same as any other Granite, a really good Pegmatite with its unique large visible crystals can usually only form in the presence of water!


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Nature = Coal

This sedimentary rock is made of the remains of plants rather than the sediments of magma-formed rocks!
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Rose Quartz, Kindergarten Teacher

I wrote this up after “Maximum Capacity”, but “Marble Madness” only offered support (and a concrete timeframe.)

The Gem homeworld is, or was, at war with an immense, unknown enemy. Part of the war effort involved harvesting planets with appropriate mineral compositions to create Gem soldiers.

Not all gem life is equal, just as not all gemstones are equal. While some gems roam free, others are delegated to lives of bondage and servitude, powering trinkets like Lapis’ mirror or the Desert Glass. Higher Gems, like Pearl, spare littlethought for the welfare of these slave gems; to them, it’s just the way of the world.

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“It is in pretty rough shape. It must finally be broken.”

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The soldiers created by the Kindergarten are slave gems–resources to be exhausted, not unique lives to be held sacred. They’re probably quartz, the second most common mineral in the earth’s continental crust. Humans use quartz as a mechanism in clocks and radios, because it’s piezoelectric–you can run electricity through it to make it vibrate, or vibrate it to produce an electric charge. But neither Gems nor humans consider it precious.

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Rose Quartz was the leader of a Gem mining operation for the homeworld. She and her crew would find likely planets, set up Kindergartens, and raise soldier gems to maturity; her maternal qualities, and maybe her specific ability to create sentient life, made her an ideal caretaker and supervisor for these operations. It was on one of these expeditions that she discovered and fell in love with the human race. Determined to save the Earth, she decides she will abort the mining operation, make up a technical excuse for her superiors, and move on to another site. Her second in command considers this treason, and threatens to report Rose to the Homeworld. There’s a confrontation.

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In the end, Rose avoids confrontation with the Homeworld by destroying the galaxy warp. No one on Homeworld hears of Rose’s treason; they presume Rose’s expedition lost. They dispatch a recovery team led by Peridot, but without warp travel, it will be six thousand years before they arrive.

Meanwhile, Rose’s expedition team, feeling hopeless and trapped, goes insane with loss and rage. They rebel, or become monsters, and all Rose can do is restrain them until she can find a way to send them home without compromising humanity. It’s possible some of the soldiers mined from the Kindergarten also turn themselves into monsters.

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Rose shuts down the kindergarten, but through some technological malfunction, one last quartz soldier is made, and rattles around the Kindergarten alone until Rose returns and finds her.

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A 16th century poem describes the origin of Amethyst–Dionysus, the god of wine and revelry, is insulted by a mortal and vows to kill the next mortal who crosses his path. This turns out to be the maiden Amethyste, and Artemis turns her into a statue of crystalline quartz to protect her. Dionysus, full of regret at his savagery, cries tears of wine which dye the quartz statue a deep purple (Amethyst is a purple variety of quartz.)

In our new mythology, Rose is the one with the magic tears, and finding Amethyst fills her with regret. To Rose, Amethyst is one last victim of the war machine which she helped propagate. She’s a directionless soldier, childlike, completely ignorant of the Gem war, and yet the Crystal Gems are faced with the task of imprisoning or killing her to protect humanity. Rose won’t allow the last of her Kindergarten charges to be destroyed, and this compassion and trust brings out Amethyst’s own beauty and goodness, and lets her forge her own unique identity as a Crystal Gem, the only good thing to come out of Rose’s Kindergarten.

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What happened to the rest of the quartz soldiers during Rose’s rebellion?

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Pearl says the Geode contains a synthetic storm, but everyone knows what’s inside a geode: Gems. In this case, hundred of quartz Gems who know nothing but lightning and combat. With the Kindergarten disabled, this will be a site of great importance in the next Gem war. If Steven can heal them the way Rose healed Amethyst, it might not be a tragedy.

Ocean Worlds: The Story of Seas on Earth and Other Planets

So far, every volume signed Jan Zalasiewicz had proved a geological pleasure (as indeed have all the others in the series on Earth Systems Science that OUP have been releasing), and this latest instalment (the second book he’s co written with Mark Williams) did not disappoint my high expectations. While it isn’t an overview of the current state of oceanography, it provides a pleasant and fascinating romp through all things ocean, from the origin of the water in comets, through their role in the great cycles of the elements to the current ecological catastrophe shaping up in the planet’s seas.

Keep reading

This is a picture I took with my phone at the Naturalis Biodiversity Center in Leiden, Netherlands. It is a scale showing how 1L (liter) of granite is lighter than 1L of basalt. This helps us visualize why plate tectonics never results in continents sinking underneath the ocean. Because continental crust is made of granite and oceanic crust is made of basalt, continents will never sink under the ocean because continents are always lighter than the ocean floor.

The pen is there for scale.