Chile Massive Earthquake and Tsunami

[SlowwHand]

Check it out. This is big.

Chile quake may have shifted Earth's axis

The 8.8 temblor likely changed the entire planet's rotation and made our days shorter, a NASA expert says.

[BlackCat]

Check it out. This is big.

1.26 microseconds to be exact - maybe tings in texas isn't that big after all

[SlowwHand]

The earth is bigger.

[BlackCat]

Most earthquakes do it but with varying effect - the 2004 sumatra 9.1 changed it 6.8 ms

[Hauldren Collider]

Can someone better at physics than I explain how this works given conservation of angular momentum?

[Berzerker]

not sure if this is right, but the subduction zone is east west and when the ocean plate snapped it lurched eastward, the same direction as our spin. If an object struck the Earth following a west to east path, the collision would have a similar effect.

[N35t0r]

Can someone better at physics than I explain how this works given conservation of angular momentum?

Momentum != velocity

The mass distribution of the earth changes, and thus, to keep angular momentum constant, rotation speed changes.

It's like an ice skater spinning... slowing down when it extends its arms, and speeding up when it tucks its arms close to the body. angular momentum is maintained, but the different mass distribution means a different rotational speed.

[N35t0r]

not sure if this is right, but the subduction zone is east west and when the ocean plate snapped it lurched eastward, the same direction as our spin. If an object struck the Earth following a west to east path, the collision would have a similar effect.

Completely different things. One is an external force acting on the earth, the other is a reshuffling of mass.

[Ecofarm]

I don't understand how the axis, or angle, of rotation changes the length of a rotation.

Whether the Earth is like this "/" or like this "|" seems to make little difference in my understanding.

The first reports I saw said it changed the axis of rotation and thus speed, was that incorrect? Or is that another affect which does not effect the rotation speed?

[onodera]

I don't understand how the axis, or angle, of rotation changes the length of a rotation.

Whether the Earth is like this "/" or like this "|" seems to make little difference in my understanding.

The first reports I saw said it changed the axis of rotation and thus speed, was that incorrect? Or is that another affect which does not effect the rotation speed?

Get a bike, put it upright, spin its front wheel hard and observe how long it takes for it to stop. Then spin it again, but now steer left and right for a while. Observe long it takes for it to stop. Of course, the friction will play its part too, but adjusting the axis will also slow it down.

[N35t0r]

Yeah, external force.


Ecofarm: I don't know much about rigid body physics, much less an actual planet, but a spinning object in (near) equilibrium will have both it's tilt and rotational speed affected if you reshuffle its mass around. AFAIK, they are both consequences of the mass reshuffling.

Where is KH when you need him to call you a moron and explain stuff?

[Hauldren Collider]

But the skater has to do positive work to change his moment of inertia in such a way. I suppose the energy probably comes from the same place the earthquake did, the heat from the earth's core, which I think has to do with the torque produced by the sun and moon. Is that right? Sorry for thread-jacking by the way...

[N35t0r]

The skater transforms stored chemical energy to do work, the earth releases whatever energy was built up in the fault/crust around it (elastic potential energy I guess), which was built up from plate movement, which is a consequence of mantle convection, which is a consequence of stored heat energy radiating out. Where this energy came from isn't really relevant WRT the conservation of momentum (but AFAIK, the sun and the moon don't exert torque on the earth) just as it isn't really relevant where the skater had lunch.

[Berzerker]

Completely different things. One is an external force acting on the earth, the other is a reshuffling of mass.

Both are external to the rate of spin and both reshuffle mass. The quake launched a huge chunk of ocean plate in the direction of Earth's spin, any "lift" from the event would slow us a bit but not enough to overcome the energy from the eastward lurch of ocean plate. I imagine even the tsunami hitting Peru would have given the Earth's spin a slight nudge.

I'm curious as to what effect 2-3 mile high ice sheets covering much of the northern hemisphere has on the Earth's tilt and spin. Thats a massive transfer of water from the oceans to the poles.

[germanos]

BBC is your friend