There is a geology joke. . .what's the difference between temptation and geologic time?

One is the wiles of the devil, and the other is a devil of a while.

I like how surfing evolved as the result of the end of the ice age. It's like, look at all this sudden meltwater! Surf's up!

Hah! I just came in here to say how happy I was to see modern day shown with SURFING.

This is super amazing. Where does it come from? I love the early 60s typefaces - looks like the educational materials I grew up with.

And, forgive my ignorance, why is time shown as a spiral?

I know, it should really be a cube.

I think that it is a spiral because if it were linear, you would need way more than one screen to view it with.

Yes, where did this image come from? There is something vaguely 60s about the drawing - but the typefaces make me suspect.

I love that it's a spiral AND I love the surfer!

Since Wolfdog didn't come back, I went digging for the answers in the Wikimedia Commons page. Turns out it's a USGS illustration and you can buy it as a poster. As near I can tell, it's pretty recent, 2007 or 8.

And, forgive my ignorance, why is time shown as a spiral?

Time is a spiral
and space is a curve
I know you get dizzy,
but try not to lose your nerve

I suspect that the depiction of time (particularly epochs) as a spiral has something to do with the "history repeats itself" adage. Some folks used to conceive of time as a circle, but others said, well, no, because some stuff changes. Going round and round + moving forward = a spiral (which, end on, looks like a circle as long as you don't bend it, though you can bend a spiral into a circle omg just blew your mind). It's a way of saying not so much "history repeats itself," but "the more things change, the more they stay the same.

D'oh, here's the quote I was trying to remember.

The past does not repeat itself, but it rhymes.
Mark Twain

I get that people conceive of time as a spiral, but I think usually they're talking about the cyclical swing of human events (war, peace; famine, abundance; big generations, small ones, etc) rather than geological time, in which less has sort of recurred (I guess warming/cooling trends...but are they in alignment in this graphic?). I was wondering whether there is a scientific reason to think of geologic time as a spiral.

Hey, sorry I didn't include a source for the picture. My guess as to "why a spiral" was just that it makes the area commensurate with how much information we have about a particular time - we can fill in lots of pictorial detail for the newest stuff, and less and less as times goes back. Also: spirals are just cool.

woah, that was a giNORmous file... shades of 1996 dialup download speeds :P

Cool, thanks Wolfdog!