Ask a geologist thread

[Faithfree]

Following Psi's lead I'm starting an "Ask a geologist" thread. I think I'm the only geologist here at present, but others might have some training in that area. Don't expect this to be a very active thread, but do your worst.

[Psi Wavefunction]

I'll start with a simple one, before Gawd gets to it:

How did the Earth come to be as it is now? How was it formed?

[Trolldor]

Ok,
Explain sedimentary drift using ping pong as ametaphor.

[Gawdzilla Sama]

How come I find seashells in Missouri? The nearest ocean is more than a mile away. (Considerably more.)

[Thinking Aloud]

I think I'm the only geologist here at present, but others might have some training in that area.

I might be able to dredge up bits of knowledge from Uni days... But it was a while ago. I'm not practicing any more! Mrs TA is still a Geophysicist though.

[Faithfree]

I think I'm the only geologist here at present, but others might have some training in that area.

I might be able to dredge up bits of knowledge from Uni days... But it was a while ago. I'm not practicing any more! Mrs TA is still a Geophysicist though.

I deem you fully qualified ; you may freely help out.

[Faithfree]

How come I find seashells in Missouri? The nearest ocean is more than a mile away. (Considerably more.)

Genesis 7: 1-24.




Ok, now that we've established how it didn't happen I need more information. Are these shells just lying around on the surface "unfossilised", or are they embedded in rock as fossils?

[Gawdzilla Sama]

How come I find seashells in Missouri? The nearest ocean is more than a mile away. (Considerably more.)

Genesis 7: 1-24.




Ok, now that we've established how it didn't happen I need more information. Are these shells just lying around on the surface "unfossilised", or are they embedded in rock as fossils?

Fossilized. I must recount the story about my fundie cousin looking at my collection. "I wonder if we're even supposed to ask why God made some creatures out of stone?"

[BrettA]

I'll start with a simple one, before Gawd gets to it:

How did the Earth come to be as it is now? How was it formed?

Not a geologist... but this has come up in other fora and I'd be interested if it can be verified, honed or corrected... (I'm sure all three apply, but I'm also trying to keep this very brief). I've used this explanation for years in days gone by, summarizing various posts. This tries to answer your "how formed" question, and volcanism, weather and many other forces apply to "as it is now".

"Accretion" is the primary term and gravity / curved space is the main culprit. From the accumulated dust, rubble and debris that is attracted to a young star, rings eventually form (again, via gravity). Then one more dense area starts local accretion of surrounding debris, eventually sucking in virtually the entire ring. The process continues today of course, but the planet initially took some 500,000 years to accrete from star stuff and rubble. My $.02.

[Faithfree]

I'll start with a simple one, before Gawd gets to it:

How did the Earth come to be as it is now? How was it formed?

The creationists have it so easy - just turn the Genesis 1 and no further brain exercise is required.

Ok executive summary of Earth history:
Earth accreted from the condensation of a rotating solar nebular, simultaneously with the other planets, about 4.5 billion years ago. Initially very hot with frequent volcanism and impacts from space and in the final stages of accretion. After a few hundred million years the temperature dropped to the point where liquid oceans formed - a Goldilocks planet rife for the appearance of life. Life probably started before 3.5 billion years ago (controversial) and by 2.5 - 2 billion years ago (plus or minus quit a bit) had changed the Earth to an oxygen bearing planet rather like today. Animals emerged around 600 million years ago and have infested the Earth ever since.

[Faithfree]

I'll start with a simple one, before Gawd gets to it:

How did the Earth come to be as it is now? How was it formed?

Not a geologist... but this has come up in other fora and I'd be interested if it can be verified, honed or corrected... (I'm sure all three apply, but I'm also trying to keep this very brief). I've used this explanation for years in days gone by, summarizing various posts. This tries to answer your "how formed" question, and volcanism, weather and many other forces apply to "as it is now".

"Accretion" is the primary term and gravity / curved space is the main culprit. From the accumulated dust, rubble and debris that is attracted to a young star, rings eventually form (again, via gravity). Then one more dense area starts local accretion of surrounding debris, eventually sucking in virtually the entire ring. The process continues today of course, but the planet initially took some 500,000 years to accrete from star stuff and rubble. My $.02.

I'd agree, a pretty good summary of the start of the accretion process. The solar system is at least a second generation, being formed from the dust of earlier super nova(s).

[Gawdzilla Sama]

I'll start with a simple one, before Gawd gets to it:

How did the Earth come to be as it is now? How was it formed?

The creationists have it so easy - just turn the Genesis 1 and no further brain exercise is required.

Ok executive summary of Earth history:
Earth accreted from the condensation of a rotating solar nebular, simultaneously with the other planets, about 4.5 billion years ago. Initially very hot with frequent volcanism and impacts from space and in the final stages of accretion. After a few hundred million years the temperature dropped to the point where liquid oceans formed - a Goldilocks planet rife for the appearance of life. Life probably started before 3.5 billion years ago (controversial) and by 2.5 - 2 billion years ago (plus or minus quit a bit) had changed the Earth to an oxygen bearing planet rather like today. Animals emerged around 600 million years ago and have infested the Earth ever since.

Don't forget radioactivity! It's very important to the early story. It extended the "age of Earth" from, IIRC, 20,000,000 yo to a bit more.

[Faithfree]

Ok,
Explain sedimentary drift using ping pong as ametaphor.

Ping pong would indeed be a pretty good metaphor for aeolian sand deposition (ie sand dunes). As the prevailing wind changes during the year individual sand grains ping pong back and forth, ultimately getting very well rounded - like ping pong balls.

[cowiz]

Can you lend me $100?

[Faithfree]

Can you lend me $100?

No