NYCPHP Meetup

[John Lacey]

Matt Morgan wrote:


> Hey, I'm a geologist (by academic training, anyway). Dirt comes from 
> rock. The oldest possible dirt would then be about 3.5 billion years 
> old, since the oldest rocks on the planet are about that old; but any 
> dirt formed that long ago would have become rock again at some point in 
> its history.
> 
> Given the periodicity of subduction/orogeny, probably no dirt ever gets 
> to be more than a couple hundred million years old before being washed 
> out to sea, sedimented to the ocean floor, and either compressed into 
> sedimentary rock, or failing that, subducted and either remelted 
> (becoming igneous rock upon cooling) or metamorphosed. Of course most 
> dirt would turn into sedimentary rock much more quickly than that: 
> sedimentary rocks form on scales on the order of hundreds of thousands 
> to millions of years, rather than tens or hundreds of millions.
> 
> There are places where, theoretically, dirt could last longer--I'm 
> thinking of the trailing edges of the continental shields, like the east 
> coasts of North and South America (among others). Those places are 
> stable, at least until the worldwide pattern of plate tectonics 
> collapses into some other pattern. That happens roughly every 500 
> million years or so (don't quote me on that--but I bet I'm right within 
> a factor of 2). But really most dirt would get buried and turn into 
> sedimentary rock relatively quickly, anyway.
> 
> Thanks for asking!!
> 
> --Matt
>

One day, a Pretty Sharp Guy decided to ask God about some stories he'd 
heard.

[PSG] umm... Hi God, what's happenin'?
[G] The Usual...
[PSG] Mind if I ask you a coupla questions?
[G] Shoot, you've got the floor.
[PSG] Is it true you can make stuff?
[G] What kind of stuff do you mean?
[PSG] You know, "stuff".  o O (if he's God, he should know what I mean)
[G] I know what you mean, but I like when people ask me specifics.
[PSG] o O (how did he know what I was thinking?)
[G] waits...
[PSG] Well, I heard you can make things. Ants, bugs n' stuff like that.
[G] This is True.
[PSG] And bigger n' more complicated things like dogs and platypusses.
[G] Well, I just slapped the platypus together real quick.
[PSG] I even hear that you make donkeys.
[G] Yep.
[PSG] Donkeys are pretty stupid.  I could probably make one myself.
[G] You think?
[PSG] Sure, it's just a matter of puttin' the ingredients together.  It 
can't be THAT hard to do.
[G] You're right.  It's easy.
[PSG] I think I'll just show you how it's done.  (goes to get some dirt)
[G] WAIT!!
[PSG] What?
[G] Get your own dirt.