Dear coastal Alaska:
Pay attention & be ready to head inland.

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.
We detect tsunami through data from ocean buoys:
1. Coastal buoys that tell us how big a tsunami is as it comes on shore
2. Deep sea (DART) buoys that detect the pressure wave of tsunami traveling in open ocean.

But first a potential tsunami needs to reach the buoys.
Tsunami are so freaking huge that they behave like shallow-water waves even in open ocean. That’s convenient physics because it makes calculating travel time simpler.

In open ocean, tsunami travel at airplane speeds.
Near shore, tsunami travel at highway speeds.
It COULD BE that a tsunami is only centimeters big. It still exists, we can still detect it, but it’s mostly harmless. (Aside from nasty & potentially deadly currents; no frolicking in the surf!)

Or it COULD BE huge and devastating. TBD.

But we know arrival times:
Every tsunami has a frequency: timing between wave crests.

Sometimes that frequency aligns with the resonance frequency of bays or fjords. Then constructive interferences amplifies tsunami into seiche, building bigger than the original waves.

It’s devastating when that happens.
Alaskan earthquakes have a nasty tendency to produce tsunami that resonate into seiche among the many nooks & crannies of the surrounding coasts. Famous examples are 1964 Port Alberti, BC & 1946 Hilo Bay, Hawaii.
Of all the geohazards, tsunami evac routes & vertical refuges (very strong tall buildings in flat coastal areas) have the most consistent international signage.

Even if you don’t speak local language, look for signs of cresting waves & follow the arrows to safety. Cresting wave labeled tsunami evacuation routeCresting wave with Hebrew textStick figure running from a crested wave towards a buildingPerson running uphill away from a cresting wave
Note: Tsunami do NOT look like cresting waves and you cannot surf them.

They look like a rapid tide. Crest or trough can hit first (50/50 random chance), so it may be ocean pulling back or rapidly rising. Tsunami are MULTIPLE waves & first wave isn’t necessarily the biggest.
Tsunami can be triggered by any major displacement of the water column: earthquake moving sea floor, landslide, glacier calving, even asteroid impact.

Today’s quake was large magnitude (M7.5), but far from population centers thus low impact:…
Quick aside on the quake:

Initial assessments of limited data often get revised as we get more data & have human interpretation instead of automated alerts. It’s normal the quake magnitude calculation adjusted from M7.4 to M7.5.

This is a neat initial interp of plate movement:
And we’re clear!

Mostly: Nearby Alaskans should keep paying attention.

Details & source:… Screenshot of the tsunami warning update including text “T
As for Alaska:
Local tsunami observation is 2ft inundation, roughly on par with high tides or storm waves.

It’s still dangerous because tsunami produce EXTREMELY strong currents, so please stay out of the water.

Details & source:… Screenshot of the linked tsunami warning update highlighting
Thus (hopefully) concludes our live-action disaster drill reminding us that those of us in the PNW live on unstable ground with a temperamental ocean.

Feeling anxious? Here’s my starter-tips for disaster prep you can do RIGHT NOW:
It’s a bad day to frolic in the surf, redux:

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More from @mikamckinnon

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).
Read 11 tweets
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 (…), but all the faults close enough to be part of this swarm are too tiny to produce anything bigger than an M5.

Read 5 tweets
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.
Read 10 tweets
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.
Read 14 tweets
28 Sep
Hey Sonoma/Napa kin,
If you’re told to go, GO.
If you’re under warning, pack up, turn your car, & leave early if you can.

This is moving fast & fierce, and you just don’t have that many roads to gtfo fast.
Make sure you opted in to emergency alerts & that your ringer is set to max tonight.

But, uh...
it’s having some bugs in Napa & Sonoma, so also do manual checks:…

& if you’re told to evac, don’t be shy about noise. Waking your neighbours could save them.
Evac orders are expanding FAST (another set just went out). Assume anything RT’d is already old news.

Check you local officials for current danger zones.

If you have ANY special circumstances & capacity to leave early, please do. Check on your neighbours if you can.
Read 9 tweets
21 Sep
You’re in the desert. A deep, vibrant blue catches your eye.

It’s neither sky nor water. #YouFindARock!
You pick up the perfectly civic blue crystal ans consider your future life choices.

> Lick

Mmm, salty!

> Lick lick lick

So salty. Exactly salty. Just like salt, because it is salt.

Read 6 tweets

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