Notices
Results 1 to 7 of 7

Thread: Types of Mountains

  1. #1 Types of Mountains 
    Forum Sophomore
    Join Date
    Sep 2005
    Posts
    106
    1) Graben and fault-block mountain are created by a faulted block moving up or down. But from definition grabens are flat horizontal valleys but fault-block mountains are not flat horizontal plateaus? (I think a block moving up should simply create flat plateaus...) This following figure is what I mean. Why the fault-block mountains are not flat while the grabens are flat?


    2) How does a fold mountain look like and how does a fault-block mountain look like, in terms of appearance? I mean, how can I distinguish a folded mountain from a fault-block mountain? (I have seen pictures of both types of mountains, but honestly, I can't tell a single difference)

    3) "Dome mountains are the result of a great amount of melted rock pushing its way up under the earth without folding or faulting resulting in a rounded dome" (quote from web sites)
    How can this "without folding" be possible? When magma pushes rock layers upward, the rock layers above are deformed by bending, or in other words, folding...or else dome mountains can't be formed...can someone please explain why dome mountains are formed without folding?

    I hope someone can explain to me! Thank you!


    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Sophomore
    Join Date
    Sep 2005
    Posts
    106
    Can someone clarify? (especailly Q3, I don't get how rock layers of dome mountains are considered undeformed and unfolded...)


    Reply With Quote  
     

  4. #3  
    Universal Mind John Galt's Avatar
    Join Date
    Jul 2005
    Posts
    14,169
    Come on Kingwinner - a little thinking here please:

    1) a) Is the fabric (i.e. the component rock) of any portion of the crust generally homogenous or heterogenous?
    b) If it is heterogenous, would you expect a weathered landscape to show irregularities?
    c) What happens to the load of sediment carried by a river when the river slows? What is a flood plain?

    2)[Grammatical correction: What does a fold mountain look like, not how.]
    Consider context: where do you find fold mountains.
    Consider internal structure: what orientation of strata will you find in each? What fault types will dominate in each?
    Consider dimensions: enough said.

    3)Find better web sites. That is just sloppy. You are absolutely correct: of course the rocks on the dome are folded. I can only deduce that the author of the web site you quote has meant to imply 'gentle folding', or he has elsewhere distinguished between folding and deformation. In eother case, as I said, that is just sloppy.
    It is not just molten rocks that can do this. Ice raises domes in the soil in structures called, if I remember correctly, pingos. Salt diapers can generate domes and they are associated with a lot of folding. A lot of oil in the US Gulf Coast is found under such salt domes.
    Reply With Quote  
     

  5. #4  
    Forum Sophomore
    Join Date
    Sep 2005
    Posts
    106
    1a) heterogenous
    1b) yes
    1c) depositions

    2) context:
    continental-continental convergent boundary ->folded mountains

    internal structures:
    -wavelike foldings for folded mountains and no faults occur
    -faulting occurs and some blocks drop down relative to others creating fault-block mountains

    3) http://www.woodlands-junior.kent.sch...ains/types.htm
    It's from this web site, it says in dome mountains, the rock layers aren't folded! This just seems impossible to me and it's not making sense. I would take your world that the rock layers are "gently folded".
    Reply With Quote  
     

  6. #5  
    Universal Mind John Galt's Avatar
    Join Date
    Jul 2005
    Posts
    14,169
    So, just so I am certain - you've correctly answered my questions relating to 1. Does that give you the answer you needed for 1?

    On 3) I looked at the website. It is horribly simplified, but not of itself inaccurate. I think the sentence that gave you trouble is ambiguous. I suspect the author meant that no folding or faulting had caused the intrusion of magma. Either way, rest assured, there would be folding, and not always gentle. In the case of the salt domes I mentioned some rock strata are turned upside down.
    Reply With Quote  
     

  7. #6  
    Forum Sophomore
    Join Date
    Sep 2005
    Posts
    106
    Hi,

    1) Yes, that pretty much answered my question! The fault block mountains are higher so are eroded first!
    One more thing I would like to ask -- is there any difference between the meanings of a "horst" and a "plateau"?

    2) So basically one usually cannot distinguish a folded mountain from a fault-block mountain by looking at a picture and you have to get closer examination on its rock layers!

    3) The way they put in the web site is quite confusing, because in fact dome mountains have deformed, folded, upcurved rock layers! I was also told that dome mountains usually have gentler slopes and folds compared to other mountains!
    Reply With Quote  
     

  8. #7  
    Universal Mind John Galt's Avatar
    Join Date
    Jul 2005
    Posts
    14,169
    1) And the graben is filled in with sediments, that naturally are close to flat. A horst is a type of plateau. A plateau can form in any elevated area where uplift has brought the rock layers ot roughly the same height. The Tibetan plateau is cause by the collision of the two continental masses of India and Northern Asia. (Responsible for the tragic Kashmiri earthquake.)

    2)Closer examination of the rock layers and wider examination of the context and shape of the mountains.

    3) would accept the 'usually'. Remember that the vast majority of mountains around the world are fold mountains. (I am also fairly certain, as an example, that the horsts that flank the Rhine graben are made of old fold mountains.
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •