The earth is so big, and as I understand, constantly moving and roiling away inside – why isn’t there a constant low level rumble?
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The Earth’s mantle is roiling if you’re looking at it on geological timescales, but very slowly in human terms. We’re talking about the flow of what would be, under normal conditions, solid rock (the mantle is not actually liquid, as you may have been taught if you’re not too young), and you might have noticed that your average rock does not flow very fast.
Typical flow rates are on the order of mm or cm per *year*, which is far below the threshold a human could detect.
Media representations of the earth’s interior are horribly misleading.
The earth’s inner core is solid, the outer core is liquid, the mantle – making up most of the rest of the planet is also solid, but flows on geological timescales (think about a finger width per year)
The crust is largely rigid and sits on top. Nothing there would be described well as “roiling”.
Magma is a separate thing, and represents liquid generated by the partial melting of the mantle. It rises up to feed volcanoes. It’s a tiny miniscule proportion of the Earth, and often in very small pockets. That’s not to say we don’t feel it – volcanic earthquakes and deformation on the scale of mm to cm occurs when magma is intruded near the surface.
The mantle is not magma, and does not behave like magma.
[The Kola Superdeep Borehole](https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole) is the deepest hole on Earth at 12,262m deep. Still no magma. The crust is very thick relative to a human. It’s very thin relative to the Earth as a whole.
The Earth’s mantle is roiling if you’re looking at it on geological timescales, but very slowly in human terms. We’re talking about the flow of what would be, under normal conditions, solid rock (the mantle is not actually liquid, as you may have been taught if you’re not too young), and you might have noticed that your average rock does not flow very fast.
Typical flow rates are on the order of mm or cm per *year*, which is far below the threshold a human could detect.
>Churning away.
The earth’s mantle is mostly solid. The consistency is analogous to stiff clay although much harder and more rigid. It tends to flow only at very slow rates approximately similar to continental drift. Ad
That said, while most earthquakes occur relatively shallow in the earth’s lithospere, as in tens of km, every so often seismometers will pick up earthquakes from deep in the mantle.
>Churning away.
The earth’s mantle is mostly solid. The consistency is analogous to stiff clay although much harder and more rigid. It tends to flow only at very slow rates approximately similar to continental drift. Ad
That said, while most earthquakes occur relatively shallow in the earth’s lithospere, as in tens of km, every so often seismometers will pick up earthquakes from deep in the mantle.
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