So, my understanding of the Earth’s crust is that it ‘floats’ on the mantle, and is relatively thin compared to the rest of the planet.
If I was an evil Bond villain who wanted to cause some chaos, would I be able to crack the Earth’s crust with immense weight like one could do with other shells? Assume I’ve got a couple of neutron stars for the purpose (one teaspoon being the equivalent of 900 Great Pyramids). Where would be the best place to attempt my evil plan?
I’m not sure it will crack per se, as opposed to just sinking a bit. The crust isn’t terribly brittle. The glaciers of the last ice age were massive enough to push the crust down significantly, and it’s still rebounding from that depression today.
Well, if you’ve got a neutron star, problem solved. One of those weighs about twice as much as our sun, so the gravitational forces are going to pull the Earth apart before they even come in physical contact with eachother. Probably cause all kinds of havoc with the rest of the solar system too, but if it’s chaos you want that’s what you’ll get.
Seriously, this is a way to think about tectonic shifts? “Rebounds” from that event?
Tectonic shift, no. Rebound, yes. Vertical crustal motion.
A number of specifics are given after that.
Any sufficiently dense weight could bore a hole through the crust; but if you’re talking about splitting a tectonic plate so a new rift is formed, that’s something else. It would probably take not just a lot of weight but also having that weight distributed over a wide but select area.
BTW: some people hypothesize that Iceland is where a giant meteorite punched a hole through the MidAtlantic Ridge.
Large dam projects cause seismic stress and are placed so as not to create cracks and fissures.
So an evil dam overlord could probably build some big dam blockage on the Amazon, or the Mississippi, and create earthquakes.
but if I had netronium, I’d just drop little bits of it from orbit.
Firstly I’d point out that there’s already many cracks in the crust that go from the surface of the earth down past the moho into the upper mantle, and possibly even deeper. There’s the big plate boundaries like the San Andreas Fault and the Cascadia Subduction Zone, but even regional faults within plates have been shown to go all the way down.
The thing is that even though the mantle does flow, it flows incredibly slowly. The faults continue to manifest themselves into the upper mantle because the upper mantle is essentially solid over the short (geologic) time span of fault movements. Even the relatively fluid aesthenosphere flows slowly enough that if you had a chunk of it on your desk (magically kept at the same pressure and heat) it would still appear to be a normal solid rock. The idea that plates “float” around on the mantle is an okay approximation, but it’s a little misleading since basically everything involved is pretty solid. You don’t actually get to things that behave like liquids over shorter time spans until you’re much much deeper.
So, with that in mind, even if you do make a crack all the way down to the mantle (which might not even be that hard if you do it somewhere that the crust is thin), it’s not as if the mantle is going to come pouring out. When impacts were thought to have caused huge volcanic events, the resulting eruption wasn’t because it was punching a hole in the crust and allowing the liquid magma to flow out, but rather due to decompression melting, mostly of the crust itself and maybe some bits of the upper mantle.
Would flooding Death Valley be enough for a crack?
You have masses that presently penetrate the crust and enter the mantle. First you have your mountains whose roots are still part of the crust (strictly speaking) but are well below the mean level of the oceanic crust underside.
Second, you have subducting basaltic plates. One gets crumpled, the other sinks into the mantle.