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Fraser
2005-Oct-21, 04:57 PM
SUMMARY: NASA scientists have found evidence that Mars once had plate tectonics reshaping its surface. Data from Mars Global Surveyor has been stitched together to create a planetary map of magnetism. This map shows striping, where two plates were once pushed apart by new molten lava coming up from under the surface. This new lava become magnetized in the direction of Mars magnetic field at the time. Since this magnetic field flipped several times through the planet's history, the stripes provide a record of when Mars' plates were active.

View full article (http://www.universetoday.com/am/publish/mars_plate_tectonics.html)
What do you think about this story? post your comments below.

Greg
2005-Oct-22, 03:49 AM
Wow. This is very interesting. I had not suspected this finding at all. If true, then to me this means that early Mars was indeed covered with water. It is an accepted principle that liquid oceans are an integral part of plate tectonics. In other words, you cannot have one without the other. Subduction is thought to be driven by runoff deposits along continental margins which eventually builds up enough weight so that the edge of the continental shelf breaks off and sinks, taking an adjacent oceanic plate into the mantle as a new trench or subduction zone along the continental margin.
I do have some signficant doubts, however. I am not sure about the time frame and whether or not there was enough time with standing oceans to get plate tectonics going on Mars. Further geological research should answer this question if indeed ocean sedimentary rock is found in association with these deposits and in rock layers from the same time period. Perhaps it is alos possible for plate tectonics to occur withour overlying water. That would call for defining a new method for subduction to occur without water "lubrication". I included a link to help explain what I mean about oceans being integral for plate tectonics to occur on Earth.

http://www.moorlandschool.co.uk/earth/tectonic.htm

cran
2005-Oct-22, 10:12 AM
It's a good finding, and I wondered when an explanation for the Tharsis volcanoes would turn up...


Subduction is thought to be driven by runoff deposits along continental margins which eventually builds up enough weight so that the edge of the continental shelf breaks off and sinks, taking an adjacent oceanic plate into the mantle as a new trench or subduction zone along the continental margin. :question: Where does this information come from?

Greg
2005-Oct-22, 03:20 PM
I saw a nice theory outlined in a n article maybe 6 months or more ago.
I have yet to find it, probably meaning it is a somewhat marginal theory. I will post a few links I found with similar material until I do find the original source for that thought.

http://www.scotese.com/futanima.htm

http://csmres.jmu.edu/geollab/vageol/vahist/Mb-Future.html

http://www.madsci.org/posts/archives/may2000/957823034.Es.r.html

The theory is pretty straightforward. Older passive continental margins gradually deposit denser and denser sediment along their margins and over the margins of oceanic crust accreted to it by the oceanic ridge. Given enough time and deposition of these dense deposits the oceanic plate along the continental margin begins to buckle and sink, forming a new subduction zone along the continental shelf. The contintental plate would then remain stationary or even move in the opposite direction once it becomes disconnected from the mid ocean ridge.

cran
2005-Oct-22, 08:49 PM
I saw a nice theory outlined in a n article maybe 6 months or more ago.
I have yet to find it, probably meaning it is a somewhat marginal theory. I will post a few links I found with similar material until I do find the original source for that thought.

http://www.scotese.com/futanima.htm

http://csmres.jmu.edu/geollab/vageol/vahist/Mb-Future.html

http://www.madsci.org/posts/archives/may2000/957823034.Es.r.html

The theory is pretty straightforward. Older passive continental margins gradually deposit denser and denser sediment along their margins and over the margins of oceanic crust accreted to it by the oceanic ridge. Given enough time and deposition of these dense deposits the oceanic plate along the continental margin begins to buckle and sink, forming a new subduction zone along the continental shelf. The contintental plate would then remain stationary or even move in the opposite direction once it becomes disconnected from the mid ocean ridge.
Thanks for the links, Greg - I'm familiar with Chris Scotese's work, it's very good; and the others seem credible ... but the 'theory' you found has problems. If you can find the source of information again, or if you'd like to champion this theory - can you start a thread with the information you have in a more appropriate place (I guess ATM is really for cosmology; so perhaps in general science?)?

Unfortunately, this thread is not the place to discuss this idea - this is for discussing evidence, requirements, and outcomes of plate tectonics on Mars (and there, you are right in that it strengthens the argument for liquid water at or near the surface at the time of tectonic activity).

Greg
2005-Oct-24, 06:32 AM
Ok I found the source article, finally. As I feared it is a bit off the mainstream, which is why it took so long to find it.

http://www.newscientist.com/article.ns?id=mg17924104.400

Unfortunately this is one of those articles that you need to be a subscriber to see, so I found a less direct reference. You have to scroll down until you get to the section titled" Setting up subduction" for a brief summary of what Battersby is talking about.

http://www.earth-pages.com/archive/tectonics.asp

This "theory" doesn't appear to be very well worked out, and if I can I will find the article and see if there are any (more scholarly) literary references on the topic. I don't know that there is enough to start a thread on another forum, and I do think that the subject is related to the topic indirectly, enough so that it should be ok to discuss it here, since we are talking about mechanisms of plate tectonics and that is what there might be evidence for on Mars.

cran
2005-Oct-24, 01:59 PM
Sorry Greg, it doesn't appear to be a theory at all; it appears to be an essay of an idea, linking sedimentary basin formation processes with subduction zone formation processes.
Stephen Battersby (the science writer, not the expert in environmental health - a different man with the same name) has been a science journalist for many years; his by-line shows up in quite a few UK-based publications. The summary in Earth Pages News Archive (your second link) indicates that this idea has not been put forward as a theory, nor has it been treated as such -

from "Setting up subduction" Earth Pages News Archives:

"... topic is nicely reviewed by Stephen Battersby, a consultant to New Scientist (Battersby, S. 2003. Eat your crusts. New Scientist, 30 August 2003, p. 30-33).
"A possible explanation ... might therefore ... perhaps bearing ... Maybe that ... Possibly there are ... could bring these ... could permeate ... Just an idea, maybe. ... maybe a relic ... in all probability ... the eastern USA may rank with the Andes!"
The language is that of an essay, and the sort of thing that gets quickly attacked in this forum (and elsewhere) if one chooses to hold it up as a theory. I still feel it is 'off-topic" to discuss it in this thread, but I acknowledge your response and your effort in following up my question.

As I indicated before, I am much more in agreement with you regarding the rest of your earlier post, and much more interested in pursuing the ideas you raised in that regard -

Greg - If true, then to me this means that early Mars was indeed covered with water. It is an accepted principle that liquid oceans are an integral part of plate tectonics. In other words, you cannot have one without the other ... I am not sure about the time frame and whether or not there was enough time with standing oceans to get plate tectonics going on Mars ... Perhaps it is alos possible for plate tectonics to occur withour overlying water. That would call for defining a new method for subduction to occur without water "lubrication". If serpentinite can be identified on Mars, then water must have been present - I wonder if connate or mantle water is sufficient to provide the catalyst, if it seems unlikely that surface water was around long enough?
A new method, without water, would suggest a different catalyst to initiate partial melting - I don't know of any, but what I don't know could fill libraries - or, is it possible that Mars has sufficiently different mineralogy/chemistry that its mantle might not be predominantly olivine, but something with a lower melting point?

hewhocaves
2005-Oct-24, 03:42 PM
hmmmm....

I'm not sure I can jump onto this badwagon just yet. I have the following concerns.

1) the picture (here's a bigger version of it) http://www.nasa.gov/centers/goddard/images/content/135896main_pnas_102_42_connerney_fig1.tif simply shows a series of stripes along the southern half of the planet. The stripes cut across a lot. they also go from roughly the poles to the equator. That's a lot of space for a single rift valley to cover.

2) there's only one rift area. At most this means one, maybe two plates. some questions: where does the plate subduct? there's no corresponding subduciton zones (the Valles Marinares is far too small) for such a massive rift area, and there are no secondary formations like mountain ranges.

3) on earth paleo-magnetism was something that helped confirm an existing hpothesis. You can see (even with the water removed) that there was something going on with the "continents". I can't see that on Mars (and over the years, I've really tried). here's a topo map of the earth to refresh your memories:
http://denali.gsfc.nasa.gov/images/earth5_surf2.gif
there's nothing even remotely obvious like that on mars.

4) the Tharsis volcanoes and the trench really don't line up with the overall trend of the paleo-mag. Oh, they do if you fudge a little and don't let doubt creep in, but compare it with, say the hawaii seamounts. Furthermore, they don't match up with each other. (although tharsis and Olympus do match up with one another).

5) lastly, im a little cocerned with map projection issues since most of the best data is near the south pole. I'd like to see that projected onto a globe before i make further comment.

I'm not saying that some sort of crustal movement didn't occur on Mars at some point. It probably did. I'm just not sure that 'plate tectonics' is an appropriate term to use.

John

cran
2005-Oct-24, 04:48 PM
Hi John,
some fair comments on your part - of course, if the features on Mars were as obvious as on Earth, then the question would have been decided before now.
The features you say are not there, may not be there, or may not be visible on the surface - erosion, dust and loose cover can do that; we've had to use GPR and seismics to map the solid earth under desert sands on Earth.

The stripes cut across a lot. they also go from roughly the poles to the equator. That's a lot of space for a single rift valley to cover. It's not so much, especially if you want to make comparisons with Earth; most of the Pacific floor is only one half of such a region; the Mid-Atlantic Ridge stretches almost from pole to pole ...

The Valles Marinares looks more like a rift than a subduction zone.

I couldn't access the first link you provided (timed out twice) but looked at the topo map to refresh my memory...
For comparison, the following are old NASA images:
http://img409.imageshack.us/img409/6312/topographymarslg2oe.th.jpg (http://img409.imageshack.us/my.php?image=topographymarslg2oe.jpg)
It has the look of a single continent or supercontinent; perhaps compare it with Chris Scotese's Rodinia or Pangaea...
This one might show up some of the features you are looking for ...
http://img409.imageshack.us/img409/1408/marstopographyzoom6ql.th.jpg (http://img409.imageshack.us/my.php?image=marstopographyzoom6ql.jpg)

parallaxicality
2005-Oct-24, 04:50 PM
I was under the impression that half of Mars had not changed since the Bombardment. If Mars had plate techtonics, then wouldn't its southern Uplands be younger?

cran
2005-Oct-24, 05:13 PM
I was under the impression that half of Mars had not changed since the Bombardment. If Mars had plate techtonics, then wouldn't its southern Uplands be younger? No, it's uplands would be older; its equivalent of oceanic basins would be younger.

hewhocaves
2005-Oct-24, 05:17 PM
Hi John,
some fair comments on your part - of course, if the features on Mars were as obvious as on Earth, then the question would have been decided before now.
The features you say are not there, may not be there, or may not be visible on the surface - erosion, dust and loose cover can do that; we've had to use GPR and seismics to map the solid earth under desert sands on Earth.

agreed. but you'd be hard pressed to cover things like the himalayas, the mid oceanic ridge, the appalachians with sand.


It's not so much, especially if you want to make comparisons with Earth; most of the Pacific floor is only one half of such a region; the Mid-Atlantic Ridge stretches almost from pole to pole ...

true. the problem there lies in that you're talking about the lowest plates (ocean plates) and yet, on mars, these are the uplands. So it doesn't necessarily follow.


The Valles Marinares looks more like a rift than a subduction zone.


could be. i like it. sort of an "east africa" thing. If thats the case, then it could be causing some of the changes in the overall direction of the plate movements.


It has the look of a single continent or supercontinent; perhaps compare it with Chris Scotese's Rodinia or Pangaea...

I would argue against a Pangaea / rodinia. The earth 'supercontinents' are an amalgamation of several plates, not a single plate. As such, it is unlikely that they would exhibit uniformity in paleomagnetism.

A couple more thoughts.
1) I'm not sure if just two plates flies for a planet. I don't think you can get a convection current going like that.

2) the large oceanic plates exist because that's the default rock for the planet. As the planet differentiated, the lighter continental crust "floats" higher than the ocean crust. This is what allows ocean crust to subduct under continental crust. If Mars' geology is much more uniform, then this doesn't happen at all (not enough source material) and we may need an entirely new engine to explain away its surface.

3) im not sure how much we can argue that mars has been whittled down to a flat surface, either. rock is pretty darn resistant. Does anyone have good figures on the rate of martian erosion?

Duane
2005-Oct-24, 08:14 PM
I don't have time to make alot of replies to specific comments, so I'll just generalize.

One thing I noticed is the same striping as noted by hewhocaves, in that it appears to be quite centralized and does not appear to girdle the planet. While the explanation that this is analogous to ocean floor spreading on Earth is a good one, AIR it is the northern portion of Mars that is "ocean basin" like, not the highlands regions of the southern hemisphere. Having said that, the process may be similar to tectonics but different due the the much smaller planet.

Regardless, I find it interesting that theere appears to be not only episodes of spreading but also episodes of twisting or differencial spreading (well, assuming I am looking at the map right). This might explain why the Tharsis mons are not in a straight-line, although the explanation for the differencial spreading action may be a bit harder to explain in the context of tectonics.

I also don't see any area of subduction. That the Valles is a rift valley seems to be a good observation, but I would still like to see some evidence of subduction before I accept that conventional tectonics occurred at some point in Mars' history.

cran
2005-Oct-25, 07:07 PM
One thing that studying the worlds in our solar system should have taught us by now, is that very little 'out there' seems to happen in a 'conventional' or terrestrial way...

galacsi
2005-Oct-25, 08:45 PM
I fully approve the 5 remarks of Hewhocaves.
I have an other reason ; now i dont believe anymore in plate tectonic for Earth , i believe in expansion . Earth (and may be Venus and Mars) being the expanded rocky core of an ex giant planet.
But it is an other story.

hewhocaves
2005-Oct-26, 04:46 AM
thanks for the vote of confidence, Galacsi :)

um.. i wish i could return it.

One of the problems with figuring out plate tectonics from, say 2bya is that there are so little of those plates left. just a few shields, like the canadian one. So we really have no idea how it started. It's entirely possible (and maybe even likely) that Mars is an aborted attempt at plate tectonics.

Greg
2005-Oct-26, 04:47 AM
I would be interested in knowing how galacsi came to this conclusion, but it is a bit too far off topic. I will say on that only that it might be possible for Mercury to be a core remenant of a "hot Jupiter" after it has burned off its outer gaseous atmosphere, lost mass, and settled into a more distant orbit. I do not actually believe this for a variety of reasons, but considering the idea makes for a nice thought experiment.
The lack of any evidence for a subduction trench is a significant problem for there being plate tectonics on Mars similar to our own model here on Earth. The process of subduction is water dependent and therefore the lack of evidence for subduction argues against there being oceans on Mars when the rifting event was active. A trench analgous to those on Earth would not be completely filled in or erased from view over time, in my view.
There have been a few articles on this forum and some discussion about volcanic activity as it relates to a significant impact event on Mars in the past. Antoniseb had even speculated in one of his posts that a sizeable impact affecting the mantle resulted in a detected fault and volcanism pattern and I believe he speculated about fracturing of crustal plates on a large scale as well. I will try to track down this thread in a later post as my recollection of this is a bit fuzzy.
I won't pursue the one previous notion about subduction on Earth except to say that I find it plausible that pressure from dense sediment deposits along old passive continental margins (where the shelf meets the ocean baisn) would make these areas likely places to buckle and for subduction to begin during those rare times when a (continental) plate is being pushed on from two opposing directions. I am fairly sure that the link to the newscientist article which has subscriber only access identifies a source that outlines this idea in a more scientific fashion.

hewhocaves
2005-Oct-26, 12:36 PM
Hi Greg,

I like the mercury hypothesis. Intriguing.

i thnk I could simplify the subduction problem further by eliminating the water aspect. The simplest answer IMHO is no subduction zone = no place for crust to go. It is possible that someone might theorize an process where something else replaces water in the cycle (unlikely, but possible). That theorey would still need to take into account the lack of trenching and come up with another place for the crust to go.

I seem to remember something about impact events and vulcanism (i believe it had to do with Hellas being an impact basin). Something about another body nearly shattering Mars and pushing out the Tharsis and olympus areas. Anyway, it's been awhile since I'd read it.

Lastly, if that did occur, i could see slight shifting, just like if you hold onto a piece of paper at one end and push the other end toward it. you get something that looks like this:

-----~~~~~~

I think that eventually, resistance overcomes inertia and backs up the process to the point where the outflow of crust gets clogged. A major flaw in that is that the only "rift area" that we can see is the line of tharsis volcanoes (if you want to even call it that) and the paleomagnetisn doesn't even follow that pattern.

like OJ's lawyers said about Cinderella. "If the shoe don't fit, you must acquit".

galacsi
2005-Oct-30, 08:51 PM
I would be interested in knowing how galacsi came to this conclusion, but it is a bit too far off topic. I will say on that only that it might be possible for Mercury to be a core remenant of a "hot Jupiter" after it has burned off its outer gaseous atmosphere, lost mass, and settled into a more distant orbit. I do not actually believe this for a variety of reasons, but considering the idea makes for a nice thought experiment.

Greg

There is an other way of producing a rocky core , the brutal one.


Let suppose planets are mostly produced in the ice belt of the solar system , because ice make accretion possible.
All these planets fight for room and matter.
You have winners : obviously Jupiter and saturn .
And you have losers : some are expelled out of the formation zone , some relatively near like Uranus and neptune , others thrown farther away like Pluto. Some Other have been badly beaten and have lost all their volatiles in the fight because they suffered a collision.
Two giants planets colliding can produce a big cloud of gas and two rocky planets. these core have been slowed so they become inner planets.
From the many planets detected around near stars we know many giants planets have elliptic orbits. So an outsider giant planet or brown star with a collection of moons cans play havoc with the formating system.

Inner planet are not primary but secondary formed planets.

It is well known that matter inside a giant planet can be very compressed.
when the core is alone , nude without its cover of liquids and gas , it can begin to dilate. There is probably an hysteresis phenomenon preventing it to explode immediately. This dilation is the motor of earth expansion , a better explanation than plate tectonics but not completely different. Expansion can cause some plate shifting.
Rocks expanding from their native state , and also water , gases push up and eventually can erupt to the surface.Giants eruptions occurs , rifts then oceans are created.

But the old continents dont move really or only the margins are compressed or deformed. The big continents have roots.

Most of the Earth core is not made of iron but of compressed rocks , the average composition of Planet Earth is not different from the average composition of the solar system.

In the past all the continents were nearer than today , Planet earth was smaller. So if Newton and Einstein are right surface gravity was greater .
Is there is a way to design a test ?

I have been taught plate tectonics in school and at fist i was very impressed with this theory.very enthousiastic. Then i try to make the model turn with a globe and i was fast to discover it do not works except for the atlantic ocean . And if you are not too regarding. Expansion seams a better explanation , but it made not sense at all in my mind . Because i could not find a credible cause. I thought of dilation of course but it was unpractical if you believe the earth has been made just like it is now. So i just forgot the point.
Now i know better. i found an explanation .
Or i have too much imagination.

i thought this point needed a true answer ,so its done.
For your interest (? ) or your fun ( ! ).

cran
2005-Oct-30, 09:43 PM
Fraser - NASA scientists have found evidence that Mars once had plate tectonics reshaping its surface... Since this magnetic field flipped several times through the planet's history, the stripes provide a record of when Mars' plates were active.

Duane - Having said that, the process may be similar to tectonics but different due the the much smaller planet.

hewhocaves - So we really have no idea how it started. It's entirely possible (and maybe even likely) that Mars is an aborted attempt at plate tectonics.

Greg - There have been a few articles on this forum and some discussion about volcanic activity as it relates to a significant impact event on Mars in the past. Antoniseb had even speculated in one of his posts that a sizeable impact affecting the mantle resulted in a detected fault and volcanism pattern and I believe he speculated about fracturing of crustal plates on a large scale as well.

hewhocaves - I seem to remember something about impact events and vulcanism (i believe it had to do with Hellas being an impact basin). Something about another body nearly shattering Mars and pushing out the Tharsis and olympus areas. Anyway, it's been awhile since I'd read it.
Lastly, if that did occur, i could see slight shifting, just like if you hold onto a piece of paper at one end and push the other end toward it. you get something that looks like this:
-----~~~~~~
Now it's starting to make sense ... :D

Regarding subduction or subduction zones - you will only find these on Earth at continent-ocean convergent boundaries, and then only when the oceanic plate is moving (eg, there is no subduction zone where the Tethyan remnant plate (Black Sea) is being overridden by the Arabian plate, nor between Africa and Europe); recognisable surface evidence for subduction zones at continent-continent convergent boundaries, or at ocean-ocean convergent boundaries, does not appear to exist.

hewhocaves
2005-Nov-04, 06:27 AM
Cran, I apologize beforehand for nit-picking....

Your assesment regarding subduction zones is correct. The example is flawed. The Alps, the Atlas mountains, the Apennines, the Caucauses and other chains are all examples of the subduction occuring as the last bit of the Tethys plate gets push under Europe.

When two continental plates converge you get something like the Himilayas. The Appalachians were the himiayas of roughly 500 million years ago.

Whoops! I have my own mistake to correct now. The Atlas mountain chain had it's origins along with the Appaachians in the same orogeny. In fact, my old professor at Rutgers is noteworthy because he found the first bits of the african plate in the americas only a few years ago, in Sterling forest about 30 miles northwest of manhattan.

And Galasci, while imaginative, your hypothesis does fall apart rather quickly, especailly after a cursory glance at the northeast. There are too many rocks from too many places attached to the northeast. In NY we have rocks from africa, but if you go due east you get rocks from England and scandinavia!

Furthermore, the earth is well differentiated. Over the last 4.5 billion years the heavy elements (iron, et al) have had ample opportunity to settle towards the center, while the lighter silicates have risen up to the continental crust. Basalt, the primary component of the ocean floor still has a fair amount of heavy elements in it like iron, so it settles while granite does not.

And before you take the above statement to mean that differentiation does not work, consider a chicken egg. Let the yoke be the iron core and the shell be the crust. Now consider that the shell on an egg is far, far, far too thick to be an accurate representation of the earth's crust. If the shell had the thickness of a single sheet of loose leaf, it would still be too thick!

Lastly, if the continets didn't move (i.e. had "roots") then things like the Hawaiian Island chains wouldn't happen. Note on the following map the locations of the Hawaiian seamount chain and the Emperor chain.

http://pubs.usgs.gov/publications/graphics/Pacific_basin.gif

If a) the earth is mostly uniform and b) the continents are rooted, especially in the center then these mountian chains should not exist. Because a) uniform rock layers will not form hot spots or support vulcanism and b) if a volcano did exist it would be staionary, and we would get a super shield volcano like Olympus Mons.

Rest assured, Galacsi, Plate Tectonics is well documented and thought out. :-)

John

cran
2005-Nov-04, 08:01 AM
hewhocaves - Your assesment regarding subduction zones is correct. The example is flawed. The Alps, the Atlas mountains, the Apennines, the Caucauses and other chains are all examples of the subduction occuring as the last bit of the Tethys plate gets push under Europe. Indeed, as is the formation of the Himalayas and Tibetan Plateau - the point is, that these convergent zones are not associated with extensive crustal trenches (the clearest indication of a subduction zone) - in these cases, the evidence is of mountain chains and uplifted land, in some older texts they might be called 'crumple' zones or 'collisional' zones ... and their appearance from a distance above (eg a satellite) is not all that dissimilar to the long curving mountain system below the Valles Marinares ... and the point was also addressed to Duane's comment about not seeing any signs...

I am not convinced that the evidence found so far on Mars is enough to prove ongoing tectonics, or that the tectonic activity which appears to have occurred in the past resulted from the same processes which drive tectonics on Earth. hewhocaves, your point about Olympus Mons is well made - the indicators, as I see them from the maps so far provided, is that the tectonic activity (vulcanism, uplift, rifting) was not apparently global, and is plausibly connected to the formation of the Hellas Basin (assuming an impact origin) and the dissipation of the energies involved.

I'm wondering if some of the discomfort with the concept is due to the appellation of 'plate' to tectonics - 'plate tectonics' is simply the term used to embrace the processes which on Earth have led to the formation and evolution of tectonic plates - in theory, the same processes (vulcanism, uplift, rifting) can occur within a single plate on Earth, or without identifiable 'plates' on smaller bodies (Io, Europa, etc); which is why I prefer to use the term 'tectonics' without adding 'plate'.


Greg - I won't pursue the one previous notion about subduction on Earth except to say that I find it plausible that pressure from dense sediment deposits along old passive continental margins (where the shelf meets the ocean baisn) would make these areas likely places to buckle and for subduction to begin during those rare times when a (continental) plate is being pushed on from two opposing directions. What you will need to show, Greg, is that sedimentary basin formation processes are on par with subduction processes which, as far as I am aware, is a few orders of magnitude difference. And you would need to explain how it is that ~3km of compressed but unconsolidated sediments has a greater density that ~20km of consolidated rock. You would also need to explain how this occurs 'where the shelf meets the ocean basin' and why these same sediments don't simply flow down into the ocean basin. Also, you would have to explain how a 'passive margin' (which has a distinct definition in the literature, and it means 'not active') has become 'active'.

galacsi
2005-Nov-05, 12:53 PM
And Galasci, while imaginative, your hypothesis does fall apart rather quickly, especailly after a cursory glance at the northeast. There are too many rocks from too many places attached to the northeast. In NY we have rocks from africa, but if you go due east you get rocks from England and scandinavia!

Furthermore, the earth is well differentiated. Over the last 4.5 billion years the heavy elements (iron, et al) have had ample opportunity to settle towards the center, while the lighter silicates have risen up to the continental crust. Basalt, the primary component of the ocean floor still has a fair amount of heavy elements in it like iron, so it settles while granite does not.

And before you take the above statement to mean that differentiation does not work, consider a chicken egg. Let the yoke be the iron core and the shell be the crust. Now consider that the shell on an egg is far, far, far too thick to be an accurate representation of the earth's crust. If the shell had the thickness of a single sheet of loose leaf, it would still be too thick!

Lastly, if the continets didn't move (i.e. had "roots") then things like the Hawaiian Island chains wouldn't happen. Note on the following map the locations of the Hawaiian seamount chain and the Emperor chain.

http://pubs.usgs.gov/publications/graphics/Pacific_basin.gif

If a) the earth is mostly uniform and b) the continents are rooted, especially in the center then these mountian chains should not exist. Because a) uniform rock layers will not form hot spots or support vulcanism and b) if a volcano did exist it would be staionary, and we would get a super shield volcano like Olympus Mons.

Rest assured, Galacsi, Plate Tectonics is well documented and thought out. :-)

John

Hello

My hypothesis is not a black or white hypothesis. I don't refute completely the plate tectonics and i have nothing against lateral deplacement of plates.
It have several points :

Earth expand

Dilatation is the cause , producing "New" rocks

the only credible explanation i can think of is ; the rocks get hightly compressed in the past and the only way this can be is ; some upper layers have been lost . From this naturally come the idea of Planet earth as the residual core of a giant planet.

Earth have been born as a differentied planet with a lithoshere and internal layers but much more complicated than thought.
Because the center is compresse rocks not iron nickel.
Iron nickel does exist of course but in much less propostion and above these heavy density layers.

When these rocks expand they push up (and sometimes erupt to the surface. ) Pushing up they crack the lithosphere , rifting and creating oceans . Not much difference with plate tectonics here. (You see i have no problems with rocks from africa and with scandinavia in NY) It is not a test which can falsify my idea. When earth expand it is not regularly on all the surface but there are localised bulge . Due to gravity plates drift on the sides of these bulges. there again not much difference with plate tectonics.

But the geometry is different , distances are not the same , plates are deformed when the Earth's radius expand. You have to visualize the movement.

About the Hawai islands i recognise it is a good point for plate tectonics , but how to be sure it is a decisive argument ?
So i will ask you a question : how do you explain there is no Andean mountain on the eastern africa ?coast ?

cran
2005-Nov-05, 02:04 PM
Hello

My hypothesis is not a black or white hypothesis. I don't refute completely the plate tectonics and i have nothing against lateral deplacement of plates.
It have several points :

Earth expand

Dilatation is the cause , producing "New" rocks

the only credible explanation i can think of is ; the rocks get hightly compressed in the past and the only way this can be is ; some upper layers have been lost . From this naturally come the idea of Planet earth as the residual core of a giant planet.

Earth have been born as a differentied planet with a lithoshere and internal layers but much more complicated than thought.
Because the center is compresse rocks not iron nickel.
Iron nickel does exist of course but in much less propostion and above these heavy density layers.

When these rocks expand they push up (and sometimes erupt to the surface. ) Pushing up they crack the lithosphere , rifting and creating oceans . Not much difference with plate tectonics here. (You see i have no problems with rocks from africa and with scandinavia in NY) It is not a test which can falsify my idea. When earth expand it is not regularly on all the surface but there are localised bulge . Due to gravity plates drift on the sides of these bulges. there again not much difference with plate tectonics.

But the geometry is different , distances are not the same , plates are deformed when the Earth's radius expand. You have to visualize the movement.

About the Hawai islands i recognise it is a good point for plate tectonics , but how to be sure it is a decisive argument ?
So i will ask you a question : how do you explain there is no Andean mountain on the eastern africa ?coast ?
galacsi, whether or not your idea is an hypothesis, it is not really relevant to the evidence of tectonics on Mars. To put it bluntly, Expanding Earth is an ATM thread, and discussion of it belongs there, and not in Universe Today Story Comments.

cran
2005-Nov-05, 02:14 PM
So i will ask you a question : how do you explain there is no Andean mountain on the eastern africa ?coast ? Because the East Africa/Indian Ocean boundary is not a convergent margin - All of the plates involved there are moving more or less in the same direction - NNE.

galacsi
2005-Nov-05, 08:02 PM
galacsi, whether or not your idea is an hypothesis, it is not really relevant to the evidence of tectonics on Mars. To put it bluntly, Expanding Earth is an ATM thread, and discussion of it belongs there, and not in Universe Today Story Comments.

Well you are right it is an ATM thread , you have my go to put it There .

galacsi
2005-Nov-05, 08:13 PM
Because the East Africa/Indian Ocean boundary is not a convergent margin - All of the plates involved there are moving more or less in the same direction - NNE.

Well in my opinion you don't see the whole picture . America and Africa are separating so if Earth size is fixed , America plate go west and Africa plate go est. Now if you look at the Indian Ocean ridges Africa must go West or have a subduction or compression zone on its east coast. And dont forget there is a rift in east Africa normaly adding to the deplacement. And still no compression or subduction ? There is a hole in the theory.

cran
2005-Nov-06, 03:02 AM
Well in my opinion you don't see the whole picture . America and Africa are separating so if Earth size is fixed , America plate go west and Africa plate go est. Now if you look at the Indian Ocean ridges Africa must go West or have a subduction or compression zone on its east coast. And dont forget there is a rift in east Africa normaly adding to the deplacement. And still no compression or subduction ? There is a hole in the theory. Well, as you say, it's your opinion ... but trying to poke a 'hole in the theory' belongs in ATM, not in a Universe Today Story about Mars.

hewhocaves
2005-Nov-06, 04:41 AM
Agreed,

I'd be more than happy to discuss this with you Galacsi in an ATM thread. So feel free to state your points there and we'll happily move that part of the discussion there.

Or if you want to PM me, that's fine as well.

John