A Very Good Primer on Plate Tectonics -- Please Read

[MineralMan]

Much misinformation is being promulgated here on DU today, following the major earthquake off the coast of Chile. Most of that misinformation is based on a lack of knowledge of the reasons that earthquake, and others, occur.

The Unites States Geological Service has prepared a very well-done, illustrated primer on plate tectonics, the cause of this and other earthquakes. If you need a basic understanding of this, spending the time needed to read this and look at the illustrations will be very rewarding. Note: Clicking on the smaller illustrations will enlarge and expand them for easier viewing.

It is my hope that many people will go and take advantage of this information provided by our socialist government. It's free to read, since we all paid for it through our taxes. Here is the link:

http://pubs.usgs.gov/gip/dynamic/understanding.html

[Posteritatis]

1. Good to see some of this instead of conspiracy theories or whatnot

Though I'm just glad I haven't seen anyone claiming the quake is on Rove's orders yet.

[GrantDem]

95. You mean it wan't some sort of sonic, tectonic, seismic weapon test that went horribly awry?

:sarcasm:

[Statistical]

2. Someone already unrecced it. I swear some people just hate science.

[MineralMan]

3. Doesn't matter. Unrecs have nothing to do with much of anything.

Those who want the information will see the thread and read the information. The unreccers can do as they please. It just doesn't matter.

[madokie]

78. You got that right

It don't matter one iota.

[Alias Dictus Tyrant]

4. It is shameful.

Particularly considering that we paint the Republicans with that brush. Almost hypocrisy.

[Dappleganger]

6. Agreed. nt

[havocmom]

10. Nah, just sit on the Latest page and refresh every 30 seconds

There is some crank (or team of cranks) sitting there, pouncing on EVERY new thread and un-reccing them. Has nada to do with subject matter, who the OP is, or time of day. Just pissy attitude and too much time on their hands.

Some of us have done experiments. Post 'the sky is blue' and that will get un-recs.

[MineralMan]

18. And, then, the real DUers read the threads and recommend them or

vice-versa, based on their true merits. It all works out.

[havocmom]

21. yup

and those who read threads have more fun

[MineralMan]

22. They're cooler, too. It's always more fun to hang out with the

cool kids.

[obxhead]

65. Might even be some scripts written for just such a thing

[Iggo]

66. I would definitely unrec "The sky is blue."

Guess why?

[dbmk]

70. To be fair:

The recs decide what goes on the front page. So if people think that "this might be interesting, but it should not take the place of <insert thread> else on the front page" they can unrec. At least thats my theory. I only use it for the worst crap.

It is not necessarily because they disapprove.

That every thread needs a complaint about unrecs is gd annoying though.

[roamer65]

5. Subduction zone earthquakes can be very powerful. Warning to the Pacific Northwest.

The 2004 Andaman quake was a subduction zone quake as was this one in Chile. The western side of the Pacific plate is obviously pushing very hard right now. Please, west coast DU'ers be ready just in case.:hug:

I am really worried about coastal Oregon, Washington and British Columbia right now...the area of the Juan De Fuca subduction zone.

[MineralMan]

7. It's possible. But there are large earthquakes every year around

the Pacific Rim. Most often, they occur without other regions experiencing earthquakes beyond their usual frequency. Of course, that could all change at any time. Our history of recording earthquakes doesn't go back very far in geological terms.

Most likely, however, it will be some time before there is another great quake. How long a time is anyone's guess. We don't understand this well enough to predict them. Things sure are shaking in Chile, though.

[MineralMan]

Another note: The most powerful earthquake ever recorded on

this planet happened off Chile, too, in 1960. The Tsunami generated from that earthquake did some damage in Hilo, Hawaii, among other places. That one measured between 9.5 and 9.9, depending on which source you check.

[CoffeeCat]

52. What about the Anchorage quake...

...March 27, 1964?

Was that one of the world's most powerful earthquakes that was recorded?

[MineralMan]

55. It was smaller, at 9.2. The lowest number for the 1960 Chile

earthquake is 9.5. I've seen it listed as 9.9.

[tbredbeck]

61. Anchorage

1964 has the #2 spot behind 1960 Chile...

[TransitJohn]

50. Seattle is the most geologically hazardous city in the USA.

It is subject to everything. Earthquakes, flooding, tsunami, volcanic eruptions, pyroclastic flows, lahars, everything.

[kestrel91316]

92. Yeah, but on the bright side, no tornados or hurricanes.

[SkyDaddy7]

69. I am very worried, too!

I have read that there is tons of evidence of past tsunamis in that region! If happened today with all the development and people who live there now it would be catastrophic! I am not saying I want it to happen again but the longer it goes without happening the scary the thought of how bad it will be when it does!

I am not from that region so correct me if I am wrong but don't the Native Indians from that region have stories about such disasters...The Thunderbird has something to do with such stories, I think?

[Po_d Mainiac]

81. Yup

There is a periodic Tsunami that has whacked Japan. Written records in Japan coincide with physical evidence of Cascadia activity. The period between events range from 200 to about 1000 years, and the average is around 500 years. We are in the neighborhood, time wise. The last one was on Jan 26, 1700.

California is overdue as well.

IMHO...Either of these events on a magnitude in the range of the Chilean shaker, will finish the job that Washington D.C. and Wall Street have started.

http://www.columbian.com/news/2010/feb/28/chile-quake-a-reminder-to-be-ready-in-this-area/
http://geology.about.com/od/quake_preparedness/a/aa_cascadiaEQ.htm

But Mr. Murphy will probably overrule, and everything East of the Rockies will fall into the Atlantic

http://www.oregongeology.com/sub/earthquakes/coastal/OrGeoEqNTsu.htm

[SkyDaddy7]

98. Most people do not have a clue...

Just how fragile we are right now!

[Blue-Jay]

8. I still blame Cheney and his magic earthquake-maker.

Facts and science have no place here.

[roamer65]

11. It's fun to blame Cheney.

He's just evil incarnate.

[Blue-Jay]

14. There's certainly plenty of blame that points in his direction.

But when people elevate him to demi-god status, I just have to laugh.

[krispos42]

97. I'm starting to think I know where all those nukes that "accidently" were on that B-52 went.

Cheney's man-size safe from Minot, then Haiti and Chile.

Shock Doctrine in effect in Port-au-Prince and Conception. Where next?

[Maru Kitteh]

9. Thankyou!

[MineralMan]

15. You're welcome. I reviewed several presentations on the web, and

though this one was the most easily grasped. Someone did a good job with it. Thanks to the USGS for keeping us all informed about geological events on our little blue ball.

[Yurovsky]

43. Good stuff... takes me back to my college days...

taking Geology and finally grasping why it is that I'll never live in California or Japan.

Hurricanes I can live with. Earthquakes scare the bejeebus out of me.

[MineralMan]

58. Thanks. I appreciate it.

[Kablooie]

12. This document is just superstition. Everyone knows earthquakes are God wreaking vengence.

[Edweird]

13. The USGS is just a cover for HAARP, man.

:tinfoilhat:

I kid, I kid....

K&R

[Posteritatis]

31. Yeah. Everyone knows it's the other way around.

:tinfoilhat:

[HiFructosePronSyrup]

16. Have you read the woo woo forum?

Shit is cash.

[MineralMan]

20. On my way over there. Thanks....

[Codeine]

35. Wow.

A few folks from the other earthquake thread are outdoing themselves in the WooCage. I'm reading their posts with a new understanding. A new terrified understanding.

[CoffeeCat]

53. What's the woo woo forum?

I swear...how do I hang around a Website for years and miss
a woo-woo forum?

I'm always the last to know!

[SidDithers]

86. Wow...

words fail.

Sid

[Junkdrawer]

17. Are there any computer models of plate tectonics that could....

estimate the impact of secondary influences (Say, significant melting of the Greenland ice sheet).

[MineralMan]

19. I don't have the answer to that question.

I imagine that geologists have speculated on it, and the melting of the enormous ice sheets from the last ice age appear to have caused substantial earthquakes. Greenland is in an active area, as well, with Iceland sitting on top of a zone of ocean floor spreading, so I'd suppose there might well be some effect of massive melting.

We really won't know unless it happens, though. Until then, it's all forecasting. I suspect that they don't really have enough data to create a solid, reliable model, though.

[Junkdrawer]

23. I guess to begin with you would have to model the forces involved....

primarily the convection currents in the mantle. Then you would need some way to model subduction resistance. None of this would be easy.

[MineralMan]

24. No, it wouldn't. And they're not really positive about the

forces that cause the plate movements. The simplest model is the convection model, but even that one is pretty complicated, since the underside of the crust is far from simple.

I think they have a pretty good model, generally of plate movements, since they can track them for a very long period through surface evidence, but I think there's still a lot of discussion over the underlying mechanisms.

Greenland is a pretty small player, really, so I'm not sure losing the ice there would have that large of an effect, but who knows? I'm sure there are PhD. candidates working on it, though, even as we speak. I'm really more of a mineralogist than a structural geologist anyhow, and an autodidact in any case, so I daren't get into too much detail

[HiFructosePronSyrup]

29. Well it's not like we really need to just guess.

There have been many period of climate change in the past involving glaciation and the loss of glaciation. And is there any correlation between those and major earthquakes? Nope.

[Junkdrawer]

47. 10,000 years ago, Sweden had major quakes the same time the ice retreated.

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=389&topic_id=7806821&mesg_id=7807809

But yes, this effect has nothing to do with the quake today.

[Cessna Invesco Palin]

60. Unfortunately the geological record is not necessarily very good at recording...

...earthquake activity - at least down to the scale of individual earthquakes. So while we can assume that India smashing into Asia has produced many quakes, we don't have a lot of specific evidence about individual quakes. It gets even trickier in areas like Scandanavia that aren't really tectonically active. So we don't really know that much about earthquake activity in Scandanavia during the retreat of the ice sheets. Occasionally a quake will leave us some good evidence (tsunamis are prone to doing this, as you'll find bits of marine sediment where they shouldn't be) but that hardly establishes a pattern from which one can draw a conclusion like yours.

[tbredbeck]

63. not true

There is evidence of glacial rebound causing quakes.

[Junkdrawer]

51. One possible way to get a grip on the problem:

If the force of movement is derived from surface area and the resistance is primarily on the plate boundaries, you would expect that large plates would move faster than small plates because the force increases as the square while the resistance would be related to circumference. Perhaps this is why the Pacific plate produces so many quakes?

[MineralMan]

56. Yes. The Pacific plate is huge. This earthquake, though was

at the subduction zone between the Nazca plate and the South American Plate. The Pacific plate and the Nazca plate, however, are in contact further to the west.

[Posteritatis]

30. Post-glacial rebound takes thousands and thousands of years

Greenland's ice sheet shrinking somewhat in the last few years wouldn't cause an 8.8 at the other side of the planet.

[Junkdrawer]

45. As to the first statement, there are scientists who say that there...

was a big earthquake in Sweden about the same time as the retreat of the last Ice Age.

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=389&topic_id=7806821&mesg_id=7807809

As to "Greenland's ice sheet shrinking somewhat in the last few years wouldn't cause an 8.8 at the other side of the planet", of course and I said so in the same post I just cited.

[The_Commonist]

25. Interesting read...

Thanks.

[MineralMan]

27. You're more than welcome. Thanks for reading.

[Hutzpa]

26. There are so many of these researches

going on that one tends to wonder -- maybe all these research are responsible for
most of these reaction.

By the way, what the hell that space station is doing up there anyway???? Since
that thing has been up there the climate has gone from being bizarre to berserk.

[MineralMan]

28. Uff da! I'm not sure what you're trying to say...

[HiFructosePronSyrup]

32. The earth is angry because we faked the moon landing.

[MineralMan]

54. I though it was the moon bombing.

Whatever...

[Codeine]

34. DU Science, ladies and gentlemen!

Don't forget to tip your server on your way to blow your fucking brains out in despair.

[Name removed]

38. Deleted message

Message removed by moderator. Click here to review the message board rules.

[Codeine]

39. Yeah. Unrelenting stupidity has been known to do that. nt

[Hutzpa]

40. Looks like somebody is

missing their mummy.

[Codeine]

41. Oh noes! My mummy!

[Hutzpa]

42. There ya go

knew you'll float back to earth.

Sudden thrust...

[tigereye]

48. people need to get a grip...

I don't know why folks are always looking for a gloom and doom (and often irrational) explanation for everything. (well other than having a very negative set of expectations about things)

[Posteritatis]

36. If I facepalmed any harder my head would explode. (nt)

[upi402]

33. Socialist government building codes: save lives and lots of cost

I hate libertarian fools always whining about this stuff. They're the first to criticize poor countries like Haiti for crappy buildings too.

Reading that one page will give you as much info as a whole section in my college geography course.

[Baclava]

37. It's all coming apart at the seams

[Regret My New Name]

44. Locking...

Dammit! I don't have that power. Oh well.

[tigereye]

46. thanks for posting!

[rufus dog]

49. Good Job

Started to write a reply on another thread where you were getting a bit of a beating, but then abandoned you like rabid dog in the woods.

[MineralMan]

57. That's OK. I can handle it just fine.

Glad you liked the post and the reference.

The Truth Is Out There...truly.

[BrklynLiberal]

59. Thank you very much for posting this link.

[rasputin1952]

62. Good job on posting this...

helps dispel many of the myths out there...:hi:

[EFerrari]

64. Thanks!

[Maru Kitteh]

67. I forgot oe first time so, K&R.

[JournalistKev87]

68. Illinois earthquakes

There have been two earthquakes in Illinois--one in 08 and recently about a few weeks ago. They were in Southern Illinois but we could feel them in the suburbs. The one recently freaked me the fuck out. I hope Illinois doesn't start getting earthquakes regularly now.

[wial]

72. Illinois has been getting earthquakes regularly for a long time

most are tiny, but read up on the New Madrid Fault, and consider moving someplace safe. Wisconsin is out of the danger zone. DC isn't.

As for the general discussion here, it seems to be neglecting the fact global warming has also caused an expansion of the ocean, which changes the balance of huge amounts of material quite apart from glacial melting. Also, big changes anywhere could have side effects very far away on the planet. The idea if plates are not directly connected they don't interact just can't be true. Big earthquakes are felt around the world (see for instance yesterday's webicorders from the Redoubt volcano site, or any webicorder for that matter) and there is some evidence big quakes can trigger others at great distances.

It stands to reason: you've got a system under great pressure, ready to give. You apply a new energy to it. Boom.

[meeshrox]

74. The recorders at Redoubt were not recording a separate event...

The ripples created by an earthquake travel around the globe and yes, show up in seismographs all over the world. But, they record the same event. The ripples that travel so far are so subtle, that they do not have the ability to cause other earthquakes. Tectonic plates are very rigid and there is no evidence that movement in one area of the globe has ever caused movement so far away.

"The idea if plates are not directly connected they don't interact just can't be true."

Where the plates are directly connected are called plate boundaries where the bulk of tectonic forces and even volcanoes exist, like the Ring of Fire. Intraplate movement occurs, too, such as the New Madrid Fault. However, this is an old weakness in the crust from a plate boundary that tried to form, but failed. There is no reason to move from Illinois because of it. The earthquakes there are mostly tremors and the possibility for a strong earthquake is almost nil.

[Enthusiast]

71. It ain't in the bible.

:sarcasm:

[AllyCat]

73. Science? Oh no, no, no! All that plate tectonics hogwash will be out of the textbooks

as soon as we get rid of that evolution nonsense.

But there are some real nifty pix on that website.

Do I need the sarcasm thingy?

[AlbertCat]

83. Science? Oh no, no, no! All that plate tectonics hogwash will be out of the textbooks

Besides, we know it's astrology and thermology.

Are they having tsunamis in South Dakota?

Well, there ya go.....

[meeshrox]

75. Thank you for posting this!

I've been back and forth with a half-dozen DUers about solar activity, isostatic rebound, etc. causing this earthquake. It difficult to debate in a forum because I have to give so much background for each post. This is extremely helpful to everyone that is interested. Thanks again! :hug:

[DirtyDawg]

76. No, no, no....

...the reason Chile suffered such terrible earthquake wasn't 'plate tectonics', and it wasn't voodoo either...it was the fact that those ungrateful 'latinos' used the ballot box to unseat they guy RR and his CIA henchmen put into power - Pinochet, I think his name was. So you see, it was God's, or the Devil, or somebody's, will for those bad, or good, acts to occur.

[panzerfaust]

77. BS: God causes earthquakes when He needs to Smite a people for Sin

I mean really, that site is soooooooooooo 20th century, and is such an obvious waste of taxpayer money which could be used to fund true faith-based science.

{on edit: failed to capitalize "He." May The Lord forgive me this sin. I pray He will not cause the earth to move here in Texas in His Just Anger}

[IDemo]

79. I'm sure you're mistaken

It's just restless turtles.

[jwirr]

80. Thank you. I earmarked it to show to my 10 year old great grandson. nt

[1776Forever]

82. If someone has the time - How do I bookmark this post?

Thanks to the poster!

[Garbo 2004]

90. Go to top of this page on the left, above thread, click on "bookmark this thread." nt

[1776Forever]

91. Thanks! Now I know!

:hi:

[Odin2005]

84. K&R

[skyounkin]

85. Nice post.

Thanx!

I love science!

[nytemare]

87. I actully had an argument with a lady who didn't "believe" in Gondwanaland

I guess she thinks the earth was created as it is. I tried to explain Pangea and Gondwanaland to her. How it wasn't just by chance that South America looks like it could connect to Africa, or about earthquakes and volcanoes.

[kestrel91316]

93. Gawd made the east side of SA match up with the west side of Africa

to test our faith. Now go read your bible some more!

[nytemare]

94. Same reason he scattered dino bones around

:)

[TransitJohn]

96. haha

[AlinPA]

88. God makes earthquakes when he is mad at gay people by shaking the ground. nt

[renate]

89. that's very well written--thanks for the link!

:thumbsup: