Marigolds
(...the erosional myth...?)
Marigolds
(...the erosional myth...?)
| " ...Those who thought drift plausible faced the criticism of Bailey Willis, who argued that the fits were too good, because faulting during breakup and subsequent crustal erosion would surely have modified the continental outlines. If the similarity of outline held, then there could have been no significant normal faulting and no movement of one continent away from the other. Schuchert, having first argued that the fits were not good enough, later argued (the opposite) (? - sic) in this light. "Wegener," he wrote, "wants us to believe that the original fracture lines have practically retained their original geographic shape change during 120 million years. Is there a geologist anywhere who will subscribe to this startling assumption?" (Oreskes (1999), The Rejection of Continental Drift, Theory and Method in American Earth Science, p.305, Oxford University Press, 420pps) |
Fig. 1. The myth of coastal erosion. Nearly 260my (?) million years of coastal erosion in the Atlantic has had little effect on these two continents, which fit almost exactly today as they did prior to Atlantic opening.
"Look at that! After 260 or so million years, they still fit. "
":Is that right, eh?? 260m years? Wow!"
"Well, ...thereabouts, ..at least that's what the ocean floor ages tell us. Judge for yourself. There's the fit, ..and there's the map (somewhere). In other words, in the length of time it has taken for the Atlantic Ocean to open to where it is today, there has only been as much coastal erosion as you can judge from the figure."
"Gee Whizz! Not a lot, ...is it? I mean, not a lot of erosion. It's a lot of time, but not a lot of erosion. ... <thinks> ... But, ...<still thinking> ...But, stratigraphers tell us marine transgressions have levelled the land many times in the geological past. You mean to say that in the last nearly 300my the sea has hardly washed up the beach?
"Well, seems so" ...
.... ..... .....
"300my?
"260 .. "
"Yeah, but, .."
... ... ..."How do we know it's that long? I mean, really? "
"From the ocean floors. Cooling curves."
"What do you mean?"
"Well, you know, ...when you get convection an' all that hot stuff rises, ..it lifts the crust up.. Aw, ..No, wait a minute, ..it's when all the cold stuff goes down at the other end, the hot stuff rises over here, 'cos the crust gets pulled, see? And when you pull it it cracks and the pressure is off so the hot stuff rises - I think that's it. Hot stuff doesn't rise because it's hot here - it rises because it's cold way over there. I don't know why this is difficult for you. I've told you this before."
"But that's a long way away."
"Yeah, ..well, ... .. Anyway. You have to pay attention. It would help if you read a book about this stuff. Once it's risen - because it's hot - it has to cool down, see? And it shrinks when it cools. And the slope off the ridge tells you how much it shrinks. Look I'll show you <sketches> "
"Oh, right, ...I see, ..Looks nice when you draw it like that. And that means 300 million years, does it?"
"260.."
..... ....
"So it's shrunk, ...?? I mean back from where it expanded to?
"Yeah, ..Yeah, ..I suppose you could say that.. Yeah."
"So what's it doing then, ..expanding or shrinking? "
"Well, it's doing both, ..one after the other, ..but both together, ..if you see what I mean."
"And that curve tells the time..."
"Yeah."
"And this is all because of that slab at the subduction zone.."
"Yeah.."
"Sinking."
"Yeah."
"But what about the stratigraphy?"
"What stratigraphy?"
"The stratigraphy that tells us the land has been levelled by the sea many times?"
"What about it?"
"Well, .shouldn't America and Africa have been levelled by now?"
"That depends .."
"On what?"
"On how long it takes to get started."
"You mean it hasn't started yet?"
"Well, ..it doesn't look like it, does it, ..I mean look at the fit. Does that look like it's a started fit?
"I dunno."
"Look, tell you what, ..why don't you take the stratigraphic sequence, count up all the unconformities and units that look like marine transgression and divide them by 260 and see what you get."
"And what will that tell us"
"A number, you'll get a number, dummy. And then you'll have something you can talk about."
"Yeah, but..."
(Antarctic mountains - layering etched by snow - flat as a tack.)
What has caused the sea level to drop?
...Or once-upon-a-time, the sea level to rise?
(and how quickly did it happen?)