Attempts to stop love were done here in in the 1970's and 1980's (is that a century ago?) using bulldozers and other heavy equipment to create trenches, also explosives to divert flow from vents
What attempts in the 1980s are you talking about? The only that I'm aware of in the 1970s was an experimental bombing run. I'm aware of a berm attempt in the 1960s, but it was laughably undersized, 1,5-3 meters tall (I can *see over* a 1,5 meter berm :Þ) If there were some others, I would be interested in them.
Water also does not stop lava, even a whole ocean full of water
So when a lava flow hits the ocean, it just keeps going? Of course not , it hardens instantly. Yes, over
millions of eruptions over geological timeperiods it builds up islands. But that's not what we're talking about.
Here's a lava flow with 1000 times the flow volume of Kilauea:
Here it is flowing into the Jökulsár á Fjöllum:
Monstrous lava flow meets water:
Surely the lava's going to win, right?
... nope.
It shifted the riverbank a bit east, but in general, the river still flows in its original path, and it acted as a wall to stop the flow from going further east.
This was an eruption with three orders of magnitude higher flow rate than Kilauea. And it reached the river right near the start of the event. This thing was so massive that it didn't even start forming lava tubes for months - it just flowed on the surface like a molten river for dozens of kilometers, so far away that you couldn't even see the eruption - just the glowing river of lava:
But a shallow highlands river beat it. Yes, pack on a million eruptions in a row, and of course you'd build over the river, damming into a lake or whatnot. But that's not the issue at hand. Lava does not "go through any barrier". Indeed, it makes its own barriers to itself in the process of erupting. Barriers that it can't melt, because it is... well, itself. A lava flow has never melted its way through a basalt berm, whether natural or artificial; it's never happened, and can't happen. Overtopped, if it's too low? Sure. But melted? No.
(And for the record, artificial materials have even higher melting points. A hot basaltic eruption may be 1100°C, but steel melts at over 1600°C)
and then there is the problem that you are diverting the lava and making it somebody else's problem, and you are liable for problems you cause them
The same could be said about floodwater, but that doesn't stop people from doing flood control. You divert floodwaters from where they'll do the most damage to where they'll do the least. And you have plans already in place for where you would divert them in a flood scenario, and discourage people from building in the path.
This is not a vast uninhabited expanse like Iceland!
Heimaey was (and is) far more densely populated than Pahoa and Leilani Estates. And Mount Etna, which was successfully diverted twice, is pretty much the opposite of an uninhabited expanse.
All the considerations that you talk about resistance is from some Hawaiian people here, but they are a very tiny minority of the population. Also keep in mind that they don't (currently) run the government. If a way was possible it would definitely be considered, has been considered, and has been rejected. Anyway i don't want to get into these discussions too much, too many other things on my mind, as you might imagine?
No, no, I get it... I should let it drop. I'm sorry. It's just painful to see people lose everything because their government - with public support - has no interest in trying to help them. I don't mean to be adding stress to you when you're in the middle of this.
Volcanic disasters hit home for me because they're always a threat here too. The whole south side of the Reykjavík metro area is built on relatively young lava, and the volcano that made it still very much has an active magma chamber.