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Why is the earth's crust so stable? It has supported life for billions of years, yet it is just 12 mi thick [1] and floats on top of liquid rock that extends fo
by jethkl 4y ago
Why is the earth's crust so stable? It has supported life for billions of years, yet it is just 12 mi thick [1] and floats on top of liquid rock that extends for thousands of miles -- the part of earth we are most familiar with is a tiny fraction of what our planet really is. You could imagine that turbulence in the liquid below would cause currents that blast through the crust with catastrophic consequences, and that this would happen regularly. But it doesn't -- we have a small number of (super) volcanos, but they are pretty rare. I find this unnerving and remarkable. Our perception of reality -- in this case the earth beneath us -- is skewed.
[1] https://en.wikipedia.org/wiki/Structure_of_Earth https://en.wikipedia.org/wiki/Structure_of_Earth
- qbonnard 4y agoN. K. Jemisin wrote a triple Hugo winning trilogy[1] about what could happen to humanity with a sliiightly less stable crust, if you want some more unnerving ;) [1] https://en.wikipedia.org/wiki/N._K._Jemisin#Broken_Earth_series https://en.wikipedia.org/wiki/N._K._Jemisin#Broken_Earth_ser...
- adgjlsfhk1 4y agosomething that is counter intuitive is that although the mantle is often described as liquid, that description is only valid on large scales (both space and time). for comparison, the mantle is significantly less liquid than cold asfault. it's just subject to huge pressures.
- MrYellowP 4y ago> asfault asphalt?
- bell-cot 4y ago"Liquid" does not describe the Earth's mantle - https://en.wikipedia.org/wiki/Structure_of_Earth#Mantle https://en.wikipedia.org/wiki/Structure_of_Earth#Mantle It is more like cold pitch - https://en.wikipedia.org/wiki/Pitch_drop_experiment https://en.wikipedia.org/wiki/Pitch_drop_experiment
- jethkl 4y agoAgree that "rock made weak and ductile under intense heat and pressure" would probably be better than "liquid", but common language and daily experience do not apply. Whatever the dynamic processes are doing, they must have symmetry and be stable -- hot plumes of stuff don't punch through the contents in random locations.
- deleted 4y ago[deleted]
- deepsun 4y agoYet it's thankfully not that stable as is Venus's crust, otherwise we'd have much more carbon in atmosphere, so persistent hothouse effect and surface temperatures of 100+ Celsius.