Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: neilep on 28/08/2007 22:58:33
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Dearest Mountaineers,
D'ya like my mountain ?
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Nice isn't it ?..it's being delivered next Tuesday...I just need to find a place for my bird bath now as it's taking it's place !
Do Mountains have earthquakes beneath them ?..I know they are formed by tectonic plate movement (Please confirm) and that they gain...what ?..an inch a year or something ?
Is this additional height a jolt or just a gradual smooth increase ?
If I was on top of Everest for instance and there was an earthquake below..would I feel it ?
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I think mostly gradual increase with time and many earthquakes although some doozies have been known to cause quite a large increase in some places, at least I believe that's what I recall. I have been on some large mountains and felt good size earthquakes, but everest is huge and I do not know in that size of a mountain! I would think so!
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There was that dreadful earthquake a couple of years ago in the mountains of northern Pakistan, so I would imagine the answer is yes.
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I tend to agree. at least that would be my assumption!
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Gee Neil, If you put this in the GEOLOGY section you just might get an decent INFORMED answer.
(how is the sarcasm coming?)
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HEE HEE HEE!
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The voices in my head said that if I moved this topic here that I might receive a decent INFORMED answer !!
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I guess we are awaiting that answer now..JIMBOB! LOL
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THE INFORMED ANSWER
I has been noted above that earthquakes do occur under mountains chains that are being uplifted. But they also occur in deep ocean trenches. And some mountain chains almost NEVER have earthquakes. Also, some earthquakes occur where no mountains are or probably have never existed.
To elucidate:
Mountain that are being formed by plate collision experience earthquakes because of the plate collision. As one plate passes under the other, as in the Himalayas or the Alps.
Mountains that have been around for a long time and that have eroded some - or a lot - have very little, if any, earthquakes. Areas such as these include The Canadian Shield and the Grenville Front which have almost no earthquake activity. The middle region of the Sahara, where Libya produces most of its oil, is also inactive. There is a mountain range (buried)under my feet here in central Texas, but this one has been rejuvenated withing the past 60 million years so there is occasional, small earthquakes. They occur very rarely since it has been 60 MY since reactivation.
Deep Ocean Trenches are also an area of active earthquakes due to collision of tectonic plated. They just build a deep hole, that goes down, but has one side, the overriding side, that has island made by volcanic eruptions on them. The classic example is the Marianas Trench, where the deepest spot in the oceans of the world exists.
There are other causes for earthquakes as well but since the question was about mountains we will only mention these in passing.
mid-ocean ridges - spreading apart of plates causes earthquakes.
transform zones - areas where plates move against each other. Large mountains CAN be built by this process but is normally not a large factor in mountain building. Thee are some large ones in Alaska, though.
Then there are the ones no one really has enough data to explain - The Charleston, South Carolina Earthquake and the Cairo Ill. are examples of these.
Thus Endeth The Lesson - (Not being Anglican or Catholic you won't get this.}
JimBob, Esq., Geologist Extraordinare
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Earthquakes happen everywhere Neil
So their shaking you will feel
In a tree
Under the sea
Hiking on a mountain
Splashing in a fountain
In the city
They're not witty
Even on a plain
they still cause pain
Uproot trees in the wood
Crumble buidings in the hood
They happen here
They happen there
They're everywhere! [:D]
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Now you see why I wasn't a lit major [:o]
Oh, sure, if you want the INFORMED answer, check out JimBob's post.
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do they happen on a train?
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Even in the rain!
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However, there are no earthquakes on Mars (nor has there ever been an earthquake on Mars)!
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yes it would be a marsquake
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Perhaps we should also add catastrophic events to the cause of earthquakes. The impact of a large meteorite would cause an earthquake.
Gee, I didn't get them all
[:(!]
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Not on a train not in the rain stop this silly quake talk your causing me Pain!! LOL
Good Job Jim BOB!
Hey Jim Bob I live on the San Andreas fault line in Humboldt county..Petrolia, Eureka Arcata, Mckinleville Blue lake.. we get lots of tremors all the time.. most everyday.. we don't feel a lot of them.. tell me about this area .. Crescent city above us was hit by quite a large tidal wave several years back.
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Thats interesting!
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do they happen on a train?
Even in the rain!
Not on a train not in the rain stop this silly quake talk your causing me Pain!!
From Earthquakes to Dr Seuss! green eggs and ham
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I love Dr. Suess, and green eggs and ham!
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Karen, the San Andreas is a "transform" fault- which means the two sides of the fault slide past each other (also known as strike-slip fault). The fault separates two tectonic plates- everything west of the fault is on the Pacific Plate, and east of the fault is part of the North American Plate. The Pacific plate is moving north relative to the North American Plate, so if you live west of the fault (most of Humboldt County is east of the fault), you'll be rubbing noses with eskimos in Alaska in the not to distant future (geologically speaking).
Most faults are either "normal" or "reverse", depending on which side of the fault moves up or down- as opposed to transform faults like the San Andreas. Transform faults, on the other hand, are almost always very extensive in length, show considerable movement and create lots of earthquakes.
The good news for you, being on the northern end of the San Andreas in California, is that you have lots of small earthquakes. Seismologists (the folks that study earthquakes) worry most about the segments of the San Andreas that are quiet- because all that stress is buiding up in the rocks - which means a much larger earthquake the longer the segment is quiet.
Several years (actually decades) ago, an army base in Colorado was injecting some sort of waste water in deep drill holes. All of a sudden, the area around the base started to experience lots of small quakes, which made folks in nearby Denver a bit nervous. The army stopped injecting water into the wells, and the quakes stopped. Intrigued by the possibilities, several scientists at the USGS proposed drilling wells along the San Andreas, and pumping water into one of the wells while pumping water out of all the adjacent wells. The idea was to create small "controlled" earthquakes along the fault to relieve the strain in the rocks to avert a sure future catastrophe. The plans were well developed when the lawyers finally pointed out the possible liabilities in setting off a possible uncontrollable major earthquake. Interesting idea anyway?
You had some recent activity in that area didn't you- seems I remember several 4+ magnitude earthquakes just offshore- was it May and June?
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A clerihew for you...
I was in my home
When I read Bass's pome
It didn't half
Make me laugh
[;D]
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All I asked was quakes beneath a mountain ?
And lo did pass many posts from the fountain
With informed luff from Jimbob‘s face
To the quirky ge-ODE from Mr Bass !
Thanks for the excellent responses !!
BIG HUGS AND SHMISHES to you all !!
mwah mwah mwah !!
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I love Dr. Seuss, and green eggs and ham!
That sounds about right as far as time frames. a few years back we had a 7.2 and 7.0 and other 4 and 5 point aftershocks .. Those were really amazing. 1rst one knocked me over off balance while vacuuming the floor. I thought I did it hitting my cabinet with the vacuuming.. LOL The only problem with that was that I was not a drinker so I realizes after several seconds we were having a big quake . I had time to get out of the house and watch things on the street sway and move telephone poles cars trucks rolling back and forth and huge waves of the paved street rolling along like ocean waves, actually humping up and straightening out! LOL! Was creepy!
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All I asked was quakes beneath a mountain ?
And lo did pass many posts from the fountain
With informed luff from Jimbob‘s face
To the quirky ge-ODE from Mr Bass !
Thanks for the excellent responses !!
BIG HUGS AND SHMISHES to you all !!
mwah mwah mwah !!
You are welcome Sir! I would like to know more about where I live!
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a few years back we had a 7.2 and 7.0 and other 4 and 5 point aftershocks .. Those were really amazing. 1rst one knocked me over off balance while vacuuming the floor. I thought I did it hitting my cabinet with the vacuuming.. LOL The only problem with that was that I was not a drinker so I realizes after several seconds we were having a big quake . I had time to get out of the house and watch things on the street sway and move telephone poles cars trucks rolling back and forth and huge waves of the paved street rolling along like ocean waves, actually humping up and straightening out! LOL! Was creepy!
Must have been an amazing sight. I've often thought I'd like to see something like that-but when it comes right down to it I'd probably be as scared as everyone else.
Karen, what town do you live in? That way I can look on some of my fault maps and see if I can provide any further info.
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However, there are no earthquakes on Mars (nor has there ever been an earthquake on Mars)!
I thought the jury was still out as to whether there had been earthquakes (or should that be marsquakes) in the dim and distant past of Mars.
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a few years back we had a 7.2 and 7.0 and other 4 and 5 point aftershocks .. Those were really amazing. 1rst one knocked me over off balance while vacuuming the floor. I thought I did it hitting my cabinet with the vacuuming.. LOL The only problem with that was that I was not a drinker so I realizes after several seconds we were having a big quake . I had time to get out of the house and watch things on the street sway and move telephone poles cars trucks rolling back and forth and huge waves of the paved street rolling along like ocean waves, actually humping up and straightening out! LOL! Was creepy!
Must have been an amazing sight. I've often thought I'd like to see something like that-but when it comes right down to it I'd probably be as scared as everyone else.
Karen, what town do you live in? That way I can look on some of my fault maps and see if I can provide any further info.
i live in Fieldbrook , Arcata, Blue lake, And mckinleyville. We are in the middle and districts are fighting over us lol
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You are living just north of Mendocino Tripple junction- where three different tectonic plates come together. Pacific plate, North American plate and the Juan de Fuca plate. You've got it all!
No wonder you have so many earthquakes. You've got 2 major transform faults (San Andreas and Mendeoino), you live right on top of a subduction zone and have a spreading center not far offshore. No telling how many subsidary faults?
I'll try to pull together some maps and get them back to you in the next few days.
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wow karen you're in the center of everything! lol
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Yes we do!
Thanks Bass! That would be cool. I would like more knowledge about this!
I don't get as scared as I used to until I think oh my Gosh I don't know how to swim! LOL! As if I were going to be able to!LOL
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Eureka is a bit over 14 miles away! about 3o minutes from me!
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I tried to doctor up a Google Earth image?
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MF is Mendocino transform fault, SAF is San Andreas fault, SZ is subduction zone (Juan de Fuca plate is diving beneath the NA plate), spreading ridge shown on western edge of Juan de Fuca plate.
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I'd say that is pretty close we are about 15 minutes from the beach if that!
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Can you shrink the map to fit! LOL I don't know how to do it!
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Can you shrink the map to fit! LOL I don't know how to do it!
YAYYYYYYY You did it before I refreshed1 LOL
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I don't know how to do it either, I think I just got lucky
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You did good! What did you do I want to know! LOL
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Used photoshop and resized the image, then had a duece of time uploading it again
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They all seem to merge rite on the tip of our little nub! LOL So thats why we get so many little tremors!
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Used photoshop and resized the image, then had a duece of time uploading it again
Hee hee You did it right.. I have never heard the term "duece of a time" what does it mean the term duece in this case.. I know like hell of a time, but just duece used what does it mean. I always thought it was the 2 in a deck of cards?
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So like the little Duece?? coupe you don't know what I ve got!
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I think its a term I must have picked up when Sacajawea came through [;)]
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Duece coup- would have been my dream car at one time. I always drove practical cars, like the beat up old international Scout I ran around the hills in- thing was built like a tank, woefully underpowered, but would go anywhere.
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Thats funny! I want an italian sports car! LOL
Now now lets not date ourselves! LOL!
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Date myself!?
My wife wouldn't understand if I dated anyone but her.
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LOL LOL!!! Thats funny!
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You do Know I meant give up our real ages! LOL
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Are you all anywhere close to Libby Montana!
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LOL
The fact that I have grandkids dates me
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Are you all anywhere close to Libby Montana!
near Missoula, 2 1/2 hour drive to Libby
I live in the beautiful Bitterroot Valley
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Hee Hee! LOL Yes it does, But I have none and it's not from not being old enough.. me kids don't want kids anytime in the near future!
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Are you all anywhere close to Libby Montana!
near Missoula, 2 1/2 hour drive to Libby
I live in the beautiful Bitterroot Valley
My husbands Aunt Uncle and cousins all live in Libby and that neck of the woods I have only been there 1 time on our honeymoon. It was beautiful!
His Uncles name is Jon Person, harvey, Stan, Karen, and Sue Person.
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I don't remember seeing it on our way! I was 21 years old so it has been 26 years ago! LOL!
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Seismic shake hazards for northern California, from CA Bureau of Mines and Geology
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looks like you're in one of the most intense areas
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Nice map! That is a good shot!
Yep Thats what I understand.. LOL I always thought it would be a Quake that would take me out here! LOL
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I do not have a single thing anchored bolted down or otherwise stablized in me house.
I have a large crack in me wall from the quake in 1989 I have numerous cracks in my foundation I cannot afford to fix and my head is constantly at a downhill sloe in my bedroom because thats where the foundation cracked and it drops downhill there! LOL It looks fine until you walk on it and go down hill! LOL
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I do not have a single thing anchored bolted down or otherwise stablized in me house.
Not too late to start!
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Hopefully this works- from USGS site
This is a geologic map of your area
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lots of thrust faults- black lines with sawteeth (due to the size of the map- only the major faults are shown- there are likely to be many, many more smaller faults). We call these imbricate thrust zones, where there are lots of thrust faults stacked one on top of another. Sort of like cards in card deck sliding over the top of each other. Sawteeth are on the upper plate that gets pushed up over the lower plate:
[diagram=276_0]
Rocks are mostly "melanges" - (cb1 and cm2 units on map) which means mixture. A geologic melange is a mixture of different rocks caused by extensive faulting. The faults break up the rocks and the fault movements jumble them together. the blocks in your area are are mainly made up of sandstones and mudstones. Overlying this are recent marine sediments QTw (pushed up out of the ocean), river deposits Qal,Qt and too many landslides (Qls).
The root cause of most of the faulting is that you live adjacent to a subduction zone, and the North American tectonic plate is trying to push up over the top of the Juan de Fuca oceanic plate, and you just happen to be on the leading edge- where the biggest stresses are.
In plain english- get used to a "whole lot of shakin' going on". I think it would be prudent to stabalize your house and anchor heavy objects to the extent of what's affordable. I know there are some things that can be done fairly cheaply. There's probably a county department that might be able to help out or at least make suggestions. Also check in with the geology dept at Humblodt State- they can give you alot more detail.
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Thanks for the information. It is interesting about the rocks and things in this area. here where I am when we dug our wells we found our property full of clay around 4 ft one well was 2 feet down into the clay! but very wet with a real high water line.. We have two 100 ft wells and one 25ft well, but it always went dry in the summer so we closed it. It was dug and put in by a professional.. The other wells we witched for ourselves and have never had a problem with the water since. Except for broken pumps we love our water. do these faults ever effect the underground streams that supply our water?
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Most definitely. Your water supply depends on several factors, but two important factors are porosity and permeability- porsosity being the amount of available (void) space for water and permeability being the ease with which that water can move through the rocks. Earthquakes do change these conditions, especially permeability. After a good shake, your water may be more abundant, less abundant, but commonly will be a bit muddy or silty.
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I have noticed that once after the 7.2 quake several years ago. It only lasted a few hours and we turned on evry fawcit on the property to rallow the mud to run its course it was a bout three days of flushing before it was perfectly clear. we have very good well water. They test it every year. Its the best water around here. I need to fix the pump again!
I did not notice that any of the smaller quakes effected it but was suspicious of the big one and wondered if that had been the cause!
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Karen- an excellent book on California Geology, written by a non-professional for ordinary folks, but still full of information that even I didn't know:
"Assembling California" by John McPhee.
"Rising from the Plains", McPhee's story of Dave Love and Wyoming geology is also a good read.
I'm sure you can find these in the local library, or any good bookstore.
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Thanks bass.. I missd this post and just found it!
I will check it out and try to find it!
I am amazed at all the sizemic action when you look at all those lines...
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de nada
enjoy the book!