The Sky is Falling
Clearing up misconceptions: despite being in the middle of a tectonic plate, Victoria is full of microfaults from ongoing compression at the plate boundaries, causing the recent earthquakes
Not all tectonic plates are comprised of completely solid bedrock, and fractures can occur within with enough forces pushing and pulling on either side.
The plates are constantly moving and pushing against one another, and as Australia is getting pushed towards Indonesia, the compression is causing activity in the NW-SE microfaults you see in the east and south west areas in the map.
The thing is, in the geological timeline, "soon," can mean the span of thousands, if not tens of thousands of years. When people say that Victoria is due for a large earthquake or volcanic eruption soon, it could be in our lifetime (very unlikely), or long after we're gone.
Only semi-related but, despite us not having any active volcanoes like you see elsewhere around the world, we're also home to the third largest volcanic plains in the entire world with the Western Victorian Volcanic Plains.
Part of the reason why the western suburbs and beyond are generally described as flat and desolate compared to the hillier eastside suburbs.
I'll also add, in the geological timeline, the western Vic volcanics are extremely young, despite being dated around 25,000-5,000 years old.
They were also the result of the same compression activity we're experiencing today.
Not saying we'll see a volcano pop up in a Brighton backyard tomorrow, but in the span of the next thousand years, there's a possibility we might see volcanic activity there given what has been documented.
Whilst geologically young, the Werribee plains lava field is not as young as you suggest - volcanism commenced around 4.6 million years ago! Radiometric dating of lava flows exposed at the surface of the Werribee plains gives an age range of 1.4-2.7mya.
Thanks for the additional info!! While yes lava had been flowing over the area for quite a long time, it took until much later for volcanoes to spring up and form the wonderful formations we see in the West today.
I guess when people think of magma deposits, they assume explosive massive volcanos, but it can also be an incredibly slow seep from a crack somewhere in the earth.
The likely spot for a volcano would be off the coast near Mt Gambier. The volcanics get younger the further west you go with Mt Shank being the youngest at only 5,000 years ago. This, however, is not indicative of orthodox hotspot volcanism as the Australian plate is not moving east over the top of it.
Out of curiousity I tried to read up on this. I've found nothing both understandable and convincing. So I've concluded that neither of us should be correcting anyone. My takeaway is that "a lot of fault lines" is a noun phrase, which can be read as either singular (ONE lot of ...) or plural (MANY ...).
Personally I will continue to go with: There are lines. There are many lines. There IS a lot of lines.
But also: Lines are there. Many lines are there. A lot of lines ARE there.
So I've given up finding truth, therefore I also apologise for correcting you :) And sorry to everyone else for this boring chain of comments.
This map is interesting to me because my Wiradjuri friend told me that her mob would never live in East Albury because of the shaky hill. This is very old oral history, but you can see on this map that Albury is right near one of those fault lines.
That's amazing to learn about, thank you for sharing!
Considering how "young" western Victoria's volcanics are, there's plenty of oral traditions passed on about the area, which helped scientists better date the time of eruption.
It's fascinating to see how much we can learn from the people who were actually there to see it happen.
Yep, basalt mined from the Footscray and Maribyrnong area.
It's what a lot of the buildings (St Patrick's), and the footpaths are made of. Because the silica particles are so fine with zero grip, it's the reason why they turn into slippery hazards when it rains haha.
Sydney is full of sandstone which is what they use in their footpaths, and they fare much better than us.
Also there’s a decent mountain range running across most of the state. We might be living through a relatively stable era but the state has plenty of tectonic activity in its past.
Pretty much the entire western half of the state was a large igneous province in the distant past, which is why the Grampians and places like Tower Hill exist.
On the other side was a massive supervolcano, the remains of which form Wilson's Promontory.
There's a bit of an interesting idea that the lower Glenelg Gorge down near Portland was the original mouth of the Murray, The gorge is much too big to have been carved by such a low volume river. There are traces of the old course up through the Mallee. Lakes Albacutya and Hindmarsh are possibly part of the old river course. It was cut off when the land rose.
Another interesting fault changed the course of the Murray at Mathoura. It completely blocked the Murray and diverted it north into the Wakool, Eventually diverting south again. There is speculation that it may eventually go north again if that fault moves some more.
Ever since that big 2021 Mansfield earthquake seismic activity has definitely increased. I know we engineer some earthquake measures into our structures but we’d be fucked if a big ish one hit Melbourne.
Since 2009, before then there weren't any decent earthquakes unless you go back to the 80's and further. I think there may've just been a quieter period through the 90s and early 2000s
Small fault lines very rarely generate damaging earthquakes. We're at more risk of a massive one hitting new Zealand and causing tsunami damage along the coast.
Our earthquake design standard is quite conservative due to the fact that we are in a low seismicity region.
Since Geoscience Australia has relatively limited information (say compared to Japan or California) about the frequency and distribution of seismic events for its national seismic hazard assessment, the earthquake loading standard builds in a high degree of conservatism.
The magnitude of ground shaking experienced in Melbourne during the woods point earthquake got nowhere near the level that buildings are designed for these days. 🙂
No, I was making a joke that I'm the inferior version of the channel haha.
It's in reference to the "we have McDonald's at home," saying that your mum will tell you when you want McDonald's, only to be disappointed when you discover not-McDonald's sitting in the fridge
I really could, Victoria has amazing geology and I have so much to share. (Did you know Victoria's Cambrian era rocks can only be found in a tiny outcrop on Phillip island?)
My only issue is that I'm awful with social media production, interaction, algorithms and all. In an alternate timeline, I could be successful on tiktok doing short form content on interesting Victorian geology, but I have too much self respect to sell out like that haha.
Good idea actually! I guess I could share tidbits and fun geology trivia any time I want, especially when it gets people more interested in the earth sciences.
If I find the time and energy to do so, keep an eye out!
Geoscience Australia's earthquake tracker says the bigger quake was 10km deep but last night's was 2km (while the other aftershocks have been smaller and/or deeper).
I don't have a lot of knowledge about quakes, but is the shallower position maybe why it felt different to the first one? More of a ripple than a shaking.
Yeah as I understand the shallower ones are more likely to cause damage. Deeper ones the energy diffuses before hitting buildings.
The shallower ones have definitely felt a bit more chaotic to me.
Thanks for sharing! I'm from WA where we occasionally get minor earthquakes in more regional areas (ie far enough away from Perth to escape most people's attentions / not even make it onto the news) so this past week has been an eye opener for me!
The darkest blue is a definitive confirmation of a fault, with the colours becoming lighter as the degree of uncertainty increases.
Geological research is greatly limited in Victoria, and only recently have work been done in attempt to document its features. With little people in the profession however, it has been quite difficult.
As a current unimelb geo student, from what I hear the cohorts are generally increasing? We’re still good at poaching our friends from other science majors haha (and I even know some ex-Arts!)
To any undecided uni students in the comments: take a geo subject (especially one with a field trip!), you won’t regret it ☺️
This reminded me of that one time my Environmental Science teacher came into class doing air guitars from the door to his desk, and then told us, "Today we're doing... The Rock Cycle!!" then continued to air-guitar.
He was one of my fav. teacher and I went to the library on my own initiative to study Env. Science topics when he was a teacher.
Unironically, you'll sometimes find yourself in rather small squeezes in caves, or tricky maneuvers while trying to access sites, so maybe it is beneficial to be "little people" after all.
Victoria is also geologically quite young - at least the Western Plains. Not all of the continent is ancient. The place is very geologically active, but just in a relatively quiet phase right now.
I think this misconception comes from the fact that in school the very basics of earthquakes is taught. It wasn't until the big one we had in 202 that I actually learned why we get earthquakes here in Victoria. You'd think this would be explained more often, given that it's simple to understand and explain.
So there's some weird stuff that happens around earthquakes that we don't completely understand. Some animals, particularly birds, seem to be able to sense an earthquake about to happen.
Most likely they're picking up on some disturbance in the magnetic field, and it might be that even humans, who aren't sensitive to the field, can sometimes unconsciously pick up on it.
This has always been the theory, but to my knowledge (and I've researched this, because I'm one of these people), there's been no actual finding of these magnetic fields that precede earthquakes.
Seems more likely to me that some people are sensitive to the early, weak waves that go out first and travel faster. This is how the California early warning system works. But it's generally like 30-90s, not 5 min.
“
The earthquake sequence locates within the
Governor Fault Zone – a major, ancient fault structure not previously considered a source of
seismic hazard.”
Interesting! Why is it there have been a lot more Earthquakes lately versus none in the past? I do not remember a single Earthquake as a child. I remember thinking that was only something that happen in books or places like Japan. Since covid there have been multiple yearly. Has something changed?
I always remember the first "big" earthquake that Melb had and that it was caused by Gina Rineheart jumping. Cannot unforget everytime we get an earthquake now.
When it was more uncommon and happened everytime it was like, holy sht Ghost?!? Now I'm edumacated and its like huh another Earthquake. Time to check Reddit/Twitter..
•
u/AutoModerator 10d ago
Have you visited today’s Daily Discussion yet?
It’s the best place for:
Drop in and see what’s happening!
THIS IS NOT A REMOVAL NOTICE
I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.