Andy Lowry @AndyLowry@qoto.org

The Wilson Cycle: Intro

“If the continents have moved, then they have drifted like rafts and formed the ocean floors in their wake. It is to this wake that we should look first.”
~ John Tuzo Wilson

Canadian geophysicist and geologist, John Tuzo Wilson, posed the question (and the title of his article in 1966) ‘Did the Atlantic close and then re-open?’ Spoiler alert - yes. That, and his many contributions to plate tectonics, including the concept of hotspots and transform faults, led to the Wilson Cycle (also known as the Supercontinent Cycle) being named after him.

The Wilson Cycle (WC) refers to the process of continent break-up and ocean-opening followed by subduction, collision, and ocean-closing (see the diagram below). This can take tens to hundreds of millons of years (very deep time) to complete.

This quick video provides animation of the WC: https://youtu.be/I_q3sAcuzIY

Step 1 of the WC starts with a tectonically stable continent/craton, eroded down and perhaps scarred by earlier collisions. Rifting (or faulting), crustal thinning, and thermal uplift caused by tectonic stretching of the continent allows the upper mantle (plume) to rise up and fill in. This can lead to earthquakes and volcanic flows. Sometime the plume can die out leading to a failed rift, but when rifting continues, things get quite interesting.

Step 2 The fractures are deep and oriented perpendicular to the extensional direction. As the continent breaks apart, the plume develops convection cells that further the rifting and deepen the basin allowing water in. The mantle material exposed by the rifting is made of much denser (or mafic) material than continental crust (or felsic) and sinks, cools and hardens/crystallizes forming oceanic crust. A new ocean basin is created.

Step 3 The two new continents continue to drift apart; the rift becomes a young spreading ridge, and the new ocean crust sinks further into the mantle as it cools and becomes denser. Sediment is now collecting on the new ocean floors.

Step 4 The Mid Ocean Ridge (MOR) continues to create new ocean crust and the new ocean deepens as the oceanic crust matures and continues to sink into the mantle. The maturer oceanic crust is much heavier than the bordering continental crust, and cracks can develop causing the oceanic crust to flex downwards forming a young subduction zone. Part of the oceanic crust is dragged deep into trench and the water-laden oceanic crust melts due to the higher temperatures of the mantle. Volcanic Island arcs are created. The rifted continental crust is now well below the surface of the ocean.

Step 5 Divergence ceases, and convergence begins. The MOR is eventually subducted, or consumed at the ocean basin margin. Associated volcanism and subduction continues, along with collision, narrowing the ocean and mountains beginning to form. This is now part of the ocean-closing cycle.

Step 6 As the continents/cratons continue to collide, folding, faulting, and earthquakes occur creating new mountains (think of the Himalayas), while catching up bits of volcanic rock, oceanic crust and sedimentary rock. A new continent is formed.

Step 7 The continent matures and erodes. Rinse and repeat with continents colliding, forming supercontinents, and dispersing again in a much longer and even deeper time.

The Wilson Cycle is somewhat simplified and doesn’t go into all the sorts tectonic variations of rift zones and diversity of plate tectonics, but it was a landmark starting point and is a sign of Wilson’s genius. Later geologists and geophysicists stand on the shoulders of this giant. We’ll dive further into the Wilson Cycle in future posts, and have a look at the rock types created and how geologists piece together the Wilson Cycle in real rocks. It’ll be fun she said :)

#WilsonCycle #JohnTuzoWilson #OceanicCrustFormation #Mantle #Plume #MidOceanRidge #SubductionZone #MountainForming #geology #ScienceMastodon @geology

@AndyLowry @elliottrandall Never mind the drummer! How about the poor schmuck who had to sing it, play synth AND piano.. whilst ducking all those beer bottles🫣

Dan Rather and Elliott Kirschner write,

“The dumpster fire we are witnessing now has been smoldering for years, if not decades. It is what happens when people elect representatives who actively hate the idea of governance. It is what happens when people rack up victories with Fox News rants and not legislation.”

#RepublicanDisarray

https://steady.substack.com/p/burning-down-the-house

It's like a puddle saying that its little depression was fine-tuned for it!

#atheism
Tooted by a #bot!
SN# 625

In an early #medieval grave at Gültlingen a warrior was buried with a gold hilt spatha (sword) - a status symbol that displays his high rank - and a ‘Spangenhelm‘. Helmets like this were part of the equipment of the late #Roman army.
Not only the helmet was made in byzantine workshop, but so were the spatha and an ornate belt. The warrior probably served as a mercenary in the Byzantine army. Dating 460-480 AD.

Foto: Landesmuseum Württemberg

#Archaeology

The whole Speaker of the House shitshow gets even more pathetic when you realize all they’re doing is electing the student council president in charge of investigating the principal’s kid’s dick.


They have no intention of governing, this is just to vaguely sort of kind of not even really almost run the Bullshit Circus, whose main event and sole ambition is to investigate nothing.

Researching mines in northern Spain I came across this curious object. It's a canary cage designed to keep the canary alive in the event of a gas leak. If a miner saw the canary laying at the bottom of the cage it was time to abandon everything and leave the mine, but not without first closing the latched glass door and opening the valve of the oxygen bottle to save the bird. A miner would do that on their way out and take the bird with them. It's a signifier of the miner's legendary sense of solidarity, no lives lost to the mine on a miners watch. A solidarity that was also crucial in the fight for workers rights, creating safer and more humane working conditions, achievements of unionization and solidarity that some of us still enjoy today.

It’s worrying to hear Rachel Reeves talking about the need to control the size of the state

The idea of ‘big government’ came from right-wingers in the US

And has always been used as a justification to cut funding to public services and lay the groundwork for privatization

Look. I've said it before and I'll say it again. If Harry has a problem with his family then he needs to persuade the French to fund him, raise an army, invade and seize the crown.

What else was Brexit for, if not to restore traditional British approaches and values?

No functioning health service, no functioning transport, desperate public homeless and at food banks, and the the top story on bbc news is more royal nonsense. #BrokenBritain

REMINDER: Steve Scalise’s life was saved by a Black lesbian Capitol cop who covered his body with her own while she was shot in the process.   Then Scalise voted against the #EqualityAct. TWICE. That is all you need to know about him. #SteveScaliseIsTrash #NeverSteveScalise

Rishi #Sunak is an idiot. Most of the things he is promising to deliver are completely outside his control. There's no way he can deliver on these five #promises.

It would only be more ridiculous if he'd had them carved in stone.

Moreover his party have been in power for *12 years*. Does he think he's really fooling anyone pretending that it was like this when he got here?

They're just taking the piss now.

#UKpolitics #UK #UKgeneralelection

Migrating here, still have a paddle in the water at the hellsite.

Guilty pleasures: wicked snark (I'm not so good at dishing it anymore), silver Cuervo and driving fast.

I'm all about politics but enjoying the less toxic life here!

My loves: #plants #nature #cats #travel #VintageJewelry #beads #JewelryMaking #politics #architecture #antiques

I have been on Mastodon a little while and I like it here, so let’s make it official with an #introduction post

I am a 30-something gay man living in lutruwita/Tasmania, Australia. Married for 7 years, our lives are ruled by our two pugs, Oscar and Stanley. My day job is in #martech but never fear, I will basically never post about that 😅

I consume waaay too much #PopCulture particularly #ScienceFiction #fantasy #books, #movies and #tv. Also do a fair bit of #gaming on #PS5 and #Switch. Ask me about my #MarvelSnap addiction.

Also interested in #lgbtq, #sustainability, #veganism, #MentalHealth, #fitness, #running and an #AusPol tragic (I grew up in Canberra, so I think it was something in the water)

Trying to take myself less seriously 🤙

BREAKING:

losercount = 4
for {
++losercount;
printf("McCarthy appears to lose number %d vote for speaker\n", losercount);
sleep 3600;
}

well, shit

ok hurtful but true #mastodon #fediverse #selfhosted #MastoAdmin #MastoAdmins

After lurking for awhile, it's time to step forward here and say hello. Hello!

I'm a journalist with ProPublica. I live in Detroit. I wrote a book about Flint's water crisis, and the deeper story of how we make and unmake our cities. I teach creative nonfiction in Alma College's MFA program in creative writing.

I'm always listening for tips, especially ones rooted in the rich stories of Michigan and the Midwest. Know something we should look into? I'm at anna.clark@propublica.org.

If you haven't been to Monument Valley on the Navajo nation, I highly highly recommend a visit!