1) Isostatic adjustment suggests that added weight to the crust make it sinks to reach a new balance. If so, it seems to me that mountains can never build up because they can never get higher...? (as curst gets thicker, it sinks, so keeping at the same level?)

2) Depositions on ocean floor coming from a river make the crust to sink (isostatic adjustment), creating gulfs. How? And how, for example, this adjustment created the Gulf of Mexico? The crust simply sinks but keeping at the same level...I don't understand!

3) "An anticline is an upcurved fold in which the oldest layer is in the center of the fold."
This is a defintion from my text book but I am puzzled by the bolded part...what center? why oldest? :bugeye:

Can someone please explain?

1) Isostatic adjustment suggests that added weight to the crust make it sinks to reach a new balance. If so, it seems to me that mountains can never build up because they can never get higher...? (as curst gets thicker, it sinks, so keeping at the same level?)

In the process of an orogeny (mountain building), such as what is happening in the Himalayas where India is colliding with Eurasia, crust is squashed together and mountains rise faster than what the can sink. You must also rember that sialic crust (the land masses) are also much lighter that the asthenosphere (upper mantle) on which it drifts, which means that the "mountain" can only sink so deep, much like a ship on water. A ship will only sink till it has displaced its own mass in water.

2) Depositions on ocean floor coming from a river make the crust to sink (isostatic adjustment), creating gulfs. How? And how, for example, this adjustment created the Gulf of Mexico? The crust simply sinks but keeping at the same level...I don't understand!

Depositions from rivers on the ocean floor make it sink, but not a lot in terms of the thickness of oceanic crust. The reason we as humans percieve the ocean floor level to stay the same is because it happens very slowly (millions of years). Oceans form when continents rift (break apart) and forms space in which river sand and mud (i.e. sediments) is deposited.

3) "An anticline is an upcurved fold in which the oldest layer is in the center of the fold."
This is a defintion from my text book but I am puzzled by the bolded part...what center? why oldest?


When rivers deposit sediments into the ocean or a lake, new layers are always deposited on the ones underneath them. Thus the oldest layers are at the bottom. The layers gradually sink lower where it gets hot and solidifies (i.e. diagenesis). When continents collide the layers are folded, much as if you would take a piece of paper and push the two sides towards each other. The older layers at the bottom form the "center" of the fold (the buldge) and are the oldest. In a syncline (the layers are bent downwards) it is exactly the opposite.

I hope this explains some of your questions :)

Thanks a lot, LightEagle! ;)

1) So the same thing with erosion, right? When erosion occurs, the mass and weight of the mountain decrease, so it rises, but erosion is occuring much faster, so the mountain is still getting lower and lower!

One more thing I am curious, the force of gravity of the mountain (force of crust on mantle) and buoyant force (force of mantle on crust) are NOT action-reaction force pair, right?

2) Do you mean that depositions from rivers on the ocean floor make the ocean floor sink faster than the level/thickness of deposition piles up, and thus overall the ocean floor is sinking...and this lowers the area which creates gulfs like the Gulf of Mexico?!

3) I don't get what the definition means by "center"...by center, does it mean horizontally like imagining a horizontal line crossing the fold? Or vertically? Or simply the real center of the fold? (see figure for an anticline) The blue point or the red point?
http://hk.geocities.com/vkfchanhk/earthsci2.JPG

1) So the same thing with erosion, right? When erosion occurs, the mass and weight of the mountain decrease, so it rises, but erosion is occuring much faster, so the mountain is still getting lower and lower!

Yip

One more thing I am curious, the force of gravity of the mountain (force of crust on mantle) and buoyant force (force of mantle on crust) are NOT action-reaction force pair, right?]

In fact they are action-reaction pairs. Both are forces and they are working in the oppisite direction. The resultant would therefore be the difference between the two.


2) Do you mean that depositions from rivers on the ocean floor make the ocean floor sink faster than the level/thickness of deposition piles up, and thus overall the ocean floor is sinking...and this lowers the area which creates gulfs like the Gulf of Mexico?!?

Both processes take a lot of time and they are in fact in equilibrium. The ocean floor on which the sediments are deposited will only sink as fast as the weight increases from the sediments that are piled on top. In the old literature it would be called a geosyncline.

3) I don't get what the definition means by "center"...by center, does it mean horizontally like imagining a horizontal line crossing the fold? Or vertically? Or simply the real center of the fold? (see figure for an anticline) The blue point or the red point?
http://hk.geocities.com/vkfchanhk/earthsci2.JPG

One would actually not speak about the "center" of the fold, but rather the core. If you draw a horizontal line through your fold, as you did, the core would be the middle part where your blue dot is located. The oldest layer would be there.

Yip



In fact they are action-reaction pairs. Both are forces and they are working in the oppisite direction. The resultant would therefore be the difference between the two.




Both processes take a lot of time and they are in fact in equilibrium. The ocean floor on which the sediments are deposited will only sink as fast as the weight increases from the sediments that are piled on top. In the old literature it would be called a geosyncline.



One would actually not speak about the "center" of the fold, but rather the core. If you draw a horizontal line through your fold, as you did, the core would be the middle part where your blue dot is located. The oldest layer would be there.

HI!

1) But I think for action-reaction pair, both forces are always equal in magnitude and opposite in direction! However, in this case, buoyant force and force of gravity can be different...

2) If they are occuring in the same rate, how can they create a lower area relative to surrounding area, called gulf?

3) How about a syncline (downcurved fold)? In a syncline, each layer is flat before folding and also after folding there isn't a spherical core...where would be the "center", then? I am a little bit confused by the wordings... :rolleyes:

locked

Are you suggesting that the moon has a charge that interacts with the Earths magnetic field in some significant way?

- KitNyx

locked

Sorry, once again I am going to say I need references. Your arguements are illogical and erroneous to me. For example, I have never seen anything that supports huricanes being caused by momentary collapses of the Earths magnetic field. This is absurd.

- KitNyx