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Continental Drift


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#1    avs76

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Posted 08 January 2007 - 02:11 AM

Can someone please explain to me how continental drift works without the planet falling apart? What I mean is if, say, the land mass of Africa is moving north, what happens to the south, where it used to be? Do we get underwater volcanoes and such? And if this is the case, wouldn't there be underwater volcanoes in the wake of all land masses that are moving? And what happens at the 'front', the direction in which the continent is moving?

What causes these land masses to move? The continents aren't just 'floating' on the earth's crust - are they?

I have been reading about the hypothesised 'super-continent' Pangea. All the continents in their present, above-water images would fit together pretty well to form Pangea, but the continents look very different with variations in sea levels. Were sea levels the same at the time of Pangea as they are today?

I feel like a dummy as most people seem to be able to grasp this concept.


#2    carini

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Posted 08 January 2007 - 07:54 AM

Quote

Can someone please explain to me how continental drift works without the planet falling apart? What I mean is if, say, the land mass of Africa is moving north, what happens to the south, where it used to be? Do we get underwater volcanoes and such? And if this is the case, wouldn't there be underwater volcanoes in the wake of all land masses that are moving? And what happens at the 'front', the direction in which the continent is moving?

What causes these land masses to move? The continents aren't just 'floating' on the earth's crust - are they?

I have been reading about the hypothesised 'super-continent' Pangea. All the continents in their present, above-water images would fit together pretty well to form Pangea, but the continents look very different with variations in sea levels. Were sea levels the same at the time of Pangea as they are today?

I feel like a dummy as most people seem to be able to grasp this concept.



Yep the continents are basically just floating. As they move into each other the create mountains like the himalayas and where they move apart they create things like the red sea.

Thats an oversimplification, but its the general idea.


#3    SilverCougar

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Posted 08 January 2007 - 08:10 AM

Easy to read site...

I'm beginning to wonder if earth science is tought in school anymore...

Edited by SilverCougar, 08 January 2007 - 08:17 AM.

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#4    Waspie_Dwarf

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Posted 08 January 2007 - 08:10 AM

Quote

What I mean is if, say, the land mass of Africa is moving north, what happens to the south, where it used to be? Do we get underwater volcanoes and such? And if this is the case, wouldn't there be underwater volcanoes in the wake of all land masses that are moving? And what happens at the 'front', the direction in which the continent is moving?


The continents sit on huge "plates" and it is these plates that are floating.

Where plates are moving apart (divergent boundaries) you get volcanoes. As the crust moves apart magma can escape. A good example of this is the Mid-Atlantic Ridge.

Where plates are moving together (convergent boundaries) either the edges of the two place rise up and form mountain ranges (for example the Himalyas) or the edge of one plate is forced under the other (subduction). As the subducted plated is forced into the magma it will melt. The upper plate can have it's edge forced upwards which also causes mountain reanges (for example the Andes).

More on this can be found on the US Geological Survey site: Understanding plate motions.

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#5    avs76

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Posted 08 January 2007 - 01:28 PM

Thanks all contributors, the links posted were easy to follow and help shed some light.


#6    avs76

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Posted 08 January 2007 - 03:52 PM

Quote

Easy to read site...

I'm beginning to wonder if earth science is tought in school anymore...

I don't know about anymore, but when I was at school 15 years ago, we learned a bit about continental drift and such...but I haven't revised about the topic since then. I can remember putting paper cut outs of silhouettes of the continents together so they formed Pangaea (see image below and at http://en.wikipedia.org/wiki/Pangaea), then broke apart to form Gondwana ("most of the landmasses in today's southern hemisphere, including Antarctica, South America, Africa, Madagascar, Australia-New Guinea, and New Zealand, as well as Arabia and the Indian subcontinent") and Laurasia ("most of modern North America, Baltica, Siberia, Kazakhstania, and the North China and East China Cratons"). (source: Wikipedia sites for Pangaea, Gondwana and Laurasia)

The problem I have with this is that the shapes of the continents today would be different to the shapes they had in times past. For example, "the microcontinent of Avalonia, a landmass that would become the northeastern United States, Nova Scotia, and England [by England I assume they mean Britain and Ireland], broke free from Gondwana and began its journey to Laurentia" which "would become North America". However, maps showing tectonic plates don't show any division between "most of North America" and "northeastern United States, Nova Scotia, and England". (see image below and at http://en.wikipedia....Tectonic_plates) Surely there would be evidence of such a division? Why is the Rocky Mountain Range so pronounced when there is no tectonic plate activity where it lies?

Why do the continents today look basicly the same as when they formed Pangaea 250 million years ago? Where did some plates come from (e.g. the pacific plate and nazca plate) after the continents split up (e.g. Australia and South America)?

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Edited by avs76, 08 January 2007 - 04:02 PM.


#7    Samael

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Posted 08 January 2007 - 09:37 PM

Quote

Can someone please explain to me how continental drift works without the planet falling apart? What I mean is if, say, the land mass of Africa is moving north, what happens to the south, where it used to be? Do we get underwater volcanoes and such? And if this is the case, wouldn't there be underwater volcanoes in the wake of all land masses that are moving? And what happens at the 'front', the direction in which the continent is moving?

What causes these land masses to move? The continents aren't just 'floating' on the earth's crust - are they?

I have been reading about the hypothesised 'super-continent' Pangea. All the continents in their present, above-water images would fit together pretty well to form Pangea, but the continents look very different with variations in sea levels. Were sea levels the same at the time of Pangea as they are today?

I feel like a dummy as most people seem to be able to grasp this concept.


Actually, continental drift is what stops the planet from falling apart.

Think of it as crisps (potato chips) on cling film, which is floating on custard. Some of the custard solidifies, adding extra crust to the landmass. If you put a key in between two crisps floating on a single piece of cling film, they drift together. That's kind of like continental drift.

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#8    m. Moe

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Posted 08 January 2007 - 10:51 PM

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Easy to read site...

I'm beginning to wonder if earth science is tought in school anymore...

For the most part it is. But whether or not the individual pays attention is the question.

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#9    frogfish

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Posted 08 January 2007 - 11:02 PM

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I'm beginning to wonder if earth science is tought in school anymore...

It's mandatory in my district unless you test out...

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#10    Mattshark

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Posted 09 January 2007 - 12:15 AM

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It's mandatory in my district unless you test out...

I saw an article on the state of scientific education in the US in New Scientist, they where graded statte by state and 20 states failed and only 5 got an A (Mass, R.I, N.Y, California and Connecticut) and only 4 got a B.

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#11    frogfish

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Posted 09 January 2007 - 12:32 AM

It's much more accurate by District yes.gif For example, Detroit Schools bring all of Michigan down, but we have the best HS in the nation, The International Academy.

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#12    Mattshark

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Posted 09 January 2007 - 12:38 AM

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It's much more accurate by District yes.gif For example, Detroit Schools bring all of Michigan down, but we have the best HS in the nation, The International Academy.

Yes but a failing grade for scientific education for a state shows that it has some really educational problems. States like Florida, Mississippi, South Carolina, Arkinsas, Texas, Alabama will have problems in university from high school because of this.

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#13    avs76

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Posted 09 January 2007 - 06:43 AM

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For the most part it is. But whether or not the individual pays attention is the question.

Obviously, in this case, the individual did not pay attention...man it's hot today...look what's happening outside...sorry, what were you were saying? I kind of lost my train of thought there. blush.gif

Edited by avs76, 09 January 2007 - 06:44 AM.


#14    Samael

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Posted 09 January 2007 - 08:36 PM

Science is definitely taught in my school. yes.gif And it's easy.

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#15    frogfish

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Posted 09 January 2007 - 09:53 PM

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Yes but a failing grade for scientific education for a state shows that it has some really educational problems.

The DISTRICT has science problems, not the state. For example, Detroit schools have been closed for weeks because they have no superintendent.

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