14 Nov, 9 tweets, 3 min read
Irregular reminder that landslides can behave like fluids.

(Thank you for all the pings!)
Landslides get weird when there really big, and can start behaving more like fluids than solids once they’re over the half million cubic meter mark.

...which was pretty much why I wrote a thesis once upon a time: io9.gizmodo.com/why-are-huge-l…
But technically landslide are fluid-like, not fluids.

Why?

Because they’re a mixed mess of materials that act differently when moving than when still. You can’t just sample a tree trunk, some peat, and water to figure out the rheologic properties (how it flows).
Consequence:
landslides may act like fluids, but are actually much more complicated physics that utterly defy our attempts at math.

So we shrug, call them fluid-like, and create imaginary model fluids that have the same bulk behaviour without trying to grapple with real dynamics
Of the fluid-like landslides, they can be fast or slow, wet or dry, laminar (smooth flow) or turbulent. Each of these is not just different properties, but different base equations of flow.

Figuring out what kind of model fluid to match to real landslide materials is Not Easy.
Rock avalanches like Frank Slide, BC or sand avalanches like you collapse on dunes usually get modeled as frictional fluids.

Debris flows tend to model as turbulent Voellmey fluids.

Clay-rich flows tend to be plastic-sticky Bingham fluids. That’s my first guess for peat.
Clues for trying to figure out what type of fluids most closely matches this landslide:

1. It’s relatively slow. You could run away from it, maybe even briskly walk.
2. It’s smooth/laminar: those trees are staying upright.
3. It’s flowing down a very low angles slope.
This peat failure is NOT a quickclay slide.

Quickclays happen in former ocean floors where salt is integrated into the clay. Water or weight collapses the structure, triggering a landslide.

Both result in big slow dramatic flows, but are fundamentally different cause & dynamics
All big landslides are weird in their own special ways. Peat’s oddities:

1. It’s light. Like, half the density of water. That raft of trees is probably floating.

2. It compresses easily, but has lots of tensile strength: rafts hold together.

gov.scot/binaries/conte…

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# More from @mikamckinnon

13 Nov
Searles Lake is a major industrial source of evaporate minerals. Brine is pumped into shallow ponds, where desert sun evaporates water & leaves behind baby crystals to screen, harvest, wash & dry.

The minerals grow so fast they hopper: outside expands before inside fills in.
Searles Lake produces a whole bunch of halites and borates: halite, borax, selenite, ulexite (tv rock), as well as some weirder minerals like searlesite.

The pink cubical minerals are halite: table salt! Not only is it safe & tasty to lick, it’s essential for your health.
19 Oct

Dear coastal PNW:
Keep an eye on the news until we have tsunami confirmation.
Subduction zone earthquakes involve vertical movement of the sea floor. This displacement can trigger tsunami.

While we’re very, very good at forecasting how fast tsunami will travel where, we don’t know how big they’ll be until they start coming on shore.
If you’re on a coast and feel severe shaking, RUN the moment shaking stops. Don’t wait around for assessments or formal warnings, just get as far uphill & inland as you can get as quickly as possible.

Same if you ever see the ocean pull back & exposing sea floor.
4 Oct
Cute lil dropstone!

My initial interpretation:
Once upon a time and long long ago, an existing rock fell into squishy mud. Time, pressure, & natural cementing hardened the mud into rock ...with rocks stuck in it.
This isn’t the only possible story!

I’m basing my interpretation on location (beach), that the rock looks gritty (grains not crystals), and that the boundary between the colours looks raised lips (not weathering rind or contact metamorphism).
All those dimples look like places other pebbles were plucked from the host rock* as it was exposed & eroded.

(*former mud/silt/sand now mudstone/siltstone/sandstone depending on proportion of fines).
1 Oct
PSA: “Earthquake prediction” is 100% bullshit in every possible way. That account “warning” of a dangerous swarm is fear-mongering to exploit your anxiety.

Block and ignore.
We CAN NOT predict what size quake will happen when & where. Wish we could, but real-life rocks are complicated.

We CAN forecast probabilities and understand how stress fields interact. For example, the Salton Sea swarm is unrelated to the San Andreas Fault:
The darkly funny part is this not even a feasible guess.

Normal charlatans can hope chance is on their side (gizmodo.com/a-quick-guide-…), but all the faults close enough to be part of this swarm are too tiny to produce anything bigger than an M5.

Whoopsie.
30 Sep
Today’s distraction:

The winner of this match will face #Magnetite for the finals with a shot at the #MinCup2020 crown. Both are beautiful & bizarre with odd properties and a lot of charm.
Both are Safe But Boring to lick. They even have similar texture (smooth). As far as your tongue in concerned, it’s a wash. You’ll need different criteria to pick your fav.

(One #MinCup we’ll have either a Fun To Lick or a Do Not Lick finalist and I will be overjoyed)
#Fluorite is a basic calcium fluoride (CaF2), which didn’t give me headaches when memorizing composition for mineralogy exams.

Amusingly, the element is named for the mineral, not the other way around. Same for fluorescence: the effect named for the rock’s distinctive property.
30 Sep
Literally nothing about the debate tonight could possibly change how I vote, and I don’t want to deal with either rage or despair from hearing his horrid voice and cruel ideals.

So I’m focusing elsewhere.

On geologic glitter, specifically.
Today’s #MinCup2020 battle is a showdown between glitter vs magnetics.

I am forever & always #TeamShiny.
Which is losing.
#Magnetite is a pretty cool mineral. It’s key to a lot of geophysics, I like collecting it with a fridge magnet on beaches, and it makes for a cool high-impact low-effort geo demo.

But then there’s #Muscovite, a subset of mica & the essence of #TeamSparkle. It’s SO SHINY.