Pangaea & Earth's Spin

[pandacracker]

On Youtube I stumbled upon a documentary about core drilling in the Antarctic and it got me thinking.
When/if Pangaea existed would it have effected the Earths spin/axis/orbit?

And while I'm here..... How much bigger would the moon have appeared in the sky before it started to recede?

 

[EnolaGaia]

On Youtube I stumbled upon a documentary about core drilling in the Antarctic and it got me thinking.
When/if Pangaea existed would it have effected the Earths spin/axis/orbit? ...

(I assume you meant 'affected'. Pangaea didn't effect (causally create) earth's spin because the earth was already rotating long before the pre-Pangaea supercontinents formed.)

If you're referring to radical effects such as huge / catastrophic planetary wobbling or flip-flops, the answer is 'No'.

At the scale of the entire planet the effects would have been relatively small - the sort of changes it would take today's precise sensing technologies to detect.

In proportional terms the earth's solid crust is a very thin skin floating atop a largely viscous mantle / core complex. In addition, the crust components are less dense than the vast majority of the earth's bulk that underlies them. In other words - the outer crust represents only a very small fraction of the planet's mass, it has no solid connectivity by which to leverage the mantle beneath it, and it can't jerk the whole planet around.

The surface weight distribution isn't all that non-symmetrical once you recall that the oceans themselves weigh a lot.

Wegener's original theory was framed with regard to the continents as we traditionally address them - the masses extending above sea level. If those widely scattered chunks were the only bits moving around, it might suggest some effects on planetary orientation, wobble, etc., as they skidded around the surface. Wegener himself seemed to think the planet's rotation provided the motive force for sliding these visible continents around. One reason his theory lay unaccepted until after his death was that calculations indicated rotational (etc.) forces weren't strong enough to explain continental movements.

It wasn't until we discovered (a) a worldwide set of tectonic plates (of which the traditional continents are merely the tallest areas) and (b) the mainly mid-ocean ridges and subduction zones that we recognized it was these larger units that were in motion and the missing motive force was convection from below.

 

[EnolaGaia]

... And while I'm here..... How much bigger would the moon have appeared in the sky before it started to recede?

The answer depends on which theory of moon formation you believe. Even if you choose the currently dominant theory (that the moon coalesced from debris knocked out of the earth by a planetoid-sized body over 4 billion years ago ... ) the details are still subjects of speculation and debate.

Under this prevailing theory (and based on speculative simulations) it has been claimed the moon could not have coalesced any closer to the early earth than 3 earth radii and probably no farther away than circa 5 earth radii. For comparison, today's moon averages circa 60 earth radii in distance from us.

It's estimated that the apparent size of the moon in the sky was less than 1% larger in the late Mesozoic ('age of dinosaurs') compared to the present.

 

[pandacracker]

Thanks Enola, that's given me something to think about.

 

[eburacum]

Pangaea would have affected the Earth's spin, but probably not in the way you might expect.

The tides raised by the Moon are gradually slowing the Earth down; many billions of years from now the Earth should* become tidally locked to the Moon, just as the Moon is tidally locked to the Earth today. The reason why there is so much uncertainty in the estimate for tidal locking is that the tidal friction caused by the oceans and other related phenomena are all very variable; if the oceans can run freely round the world, then there is less friction, and so on. Pangaea would have been a big brake in the world ocean, slowing down global circulation, just like our continents do today (we have two big continental masses that stretch a long way from north to south, breaking up ocean circulation).

The amount of tidal friction and dissipation on the Earth varies continually over geological time, and Pangaea would have affected that.When the continents are small and far apart, and the oceans flow freely, then friction and the dissipation of energy is reduced.

*(I say should rather than will because this event is likely to occur after the Sun turns into a red giant, and probably both the Moon and the Earth will be vapourised in that event).

 

[EnolaGaia]

Pandacracker:

I finally found a single site that discusses and illustrates relative moon sizes (as observed) in the very distant past:

http://www.lpi.usra.edu/exploration/training/illustrations/earthMoon/

This higher-resolution large JPEG image:

http://www.lpi.usra.edu/exploration/training/illustrations/earthMoon/hiRes/03.jpg

... illustrates the relative sizes of the moon in the sky now, at 3.9 billion years ago, and circa 4.5 billion years ago (i.e., around the time of its formation under the big impact theory).

 

[pandacracker]

Many thanks, now I can spend more time in front of the computer which is good because I have absolutely no housework or gardening to do at all!

 

[skinny]

if the oceans can run freely round the world, then there is less friction, and so on. Pangaea would have been a big brake in the world ocean, slowing down global circulation, just like our continents do today (we have two big continental masses that stretch a long way from north to south, breaking up ocean circulation).

.

Twigs a synaptic response - I think I understand why Australia's climate is so unpredictable compared to those of the supercontinents of the northern hemisphere - we are surrounded by oceans at different and regularly alternating temps. I know this seems obvious to climatologists, but the idea has just taken root in my own tiny mind.