So there’s spreading along the Mid-Atlantic ridge, and that causes subduction in along the Pacific coastlines. So what about spreading in the Pacifiic, does that cause subduction along the Atlantic coastlines? I don’t get it. Why is there a different set of rules in the Pacific vs Atlantic.

nanny_govt_sucks (12:21:08) :

I’ll take the expanding Earth theory over the wildly spinning swirling and bumping continents theory any day. We can all see that Africa and South America separated along the mid-atlantic rift, and there was no subduction. The continents were pushed apart. The question is: Does the same thing happen in the Pacific, or are there an entirely different set of rules over there?

How do you mean there is no subduction? There are subduction zones all over the earth. The subduction does not need to occur in the same ocean basin that the spreading occurs in.

There are subduction zones along most of the west coast of south America and Central America , at the boundary of the Cocos plate and the Caribbean plate, the Nazca plate and the South American plate, There is subduction stretching from Alaska to the area east of Australia along the Aleutian Island arc down to central Japan, and down to the boundary between the Australian Plate and the Pacific plate.

The Mid Atlantic ridge is where most of the spreading is occurring, and most of the subduction driven by that spreading occurs in the Pacific basin.

You don’t need a magic expanding earth to explain it, just an understanding that some of the displacement is taken up through mountain building (Himalayas) as plates collide (Indian plate vs Eurasian plate) and some by subduction as seen on both sides of the Pacific basin as it gets squeezed.

http://en.wikipedia.org/wiki/Plate_tectonics

http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/Maps/map_plate_tectonics_world.html

Larry

Average and smooth it out over a couple of decades, and voila! It’s just a fingernail’s growth rate, just like the geophysicists say.

It is not ther same as the California boundary. Etopia is on a rift and San Francisco is on a strike-slip fault.

Retired geologist

The location of this rift used to be very close to the South Pole, 440 million years ago. It would have been under a few kilometres of glacier at the time.

On a more serious note, I love seeing our planet in action. It puts of all the crackpot greenie demands into perspective.

Take a look at Madagascar. Now look at the coast line of Mozambique.

Yup, split off some millions of years ago. India used to be down there too, long ago. Notice Madagascar is on a North East trajectory? Like India was… (though I think it is a bit more east… look out Thailand!…)

Now the rift zone is a bit further over under Africa, so we get, yes, The Great Rift Valley and Lake Victoria (and all the rift valley lake chain, really).

Basically follow the Nile from the root in the lakes along the borders of Tanzania, Kenya, etc. That is where Africa is “unzipping”; so in a few hundred million years or so there will be a new “Madagascar” like island just off shore from a slimmer Africa. It will hold what is now Mozambique, Tanzania, Kenya… The only real question is will it be a set of small islands like Mozambique, or will it become a single larger chunk like India?

Decisions, decisions…

Oh, and per the “expanding earth” theory. That was one of the common theories back in the 1950′s. Always bugged me for one simple reason:

Matter is neither created nor destroyed.

For the earth to expand: From where does the added ‘stuff’ come? …

Until you can show a stargate in the planet core with stuff coming in through a worm hole, we’re not expanding… No “stuff” to do it with.