Hot answers tagged

16

Mountain ranges are usually formed as orogeny where tectonic plates collides, known as convergent boundaries. The continental plates have less density than the oceanic plates and the buoyancy results in that they are mostly above sea level. Continental sea floor is known as continental shelf, but usually, it doesn't reach far from the coastline. Therefor ...


11

Per yesterday's What-If, If you make a building too big, the top part is heavy and it squishes the bottom part. In the context of Tibet, what this means is that rock has a yield strength: pile it up high enough and it will break (via earthquakes); and if you make a big enough pile, especially of continental material, then the concentrations of radiogenic ...


7

Part of the current topography might be due to a hot upper mantle below the Rocky mountains. This can be determined by seismic tomography. The hot mantle creates isostatic uplift. Just one of many pictures I found: http://srl.geoscienceworld.org/content/83/1/23/F2.large.jpg


6

A way to understand Rocky Mountains is (as mentioned) to look at the destiny of the Farrallon Plate. In the collision with North America, it didn't subduct but rather slide under the lithosphere until it finally get a steeper angle and subducts at the eastern rim of the Rockies. This long journey could also lead to processes causing destabilization and ...


6

Quite the opposite. Divergent boundaries can cause mountain (well, actually volcano) building, because upwelling magma is part of the rifting process. First and most importantly, the Mid-Ocean Ridge can be considered the longest, most massive mountain range in the world. It's more obvious, of course, on continental rifts like the East African Rift. Mt. ...


5

There are no plate faults in Arizona (actually "plate boundary" is the term that we use - "fault" already has a different meaning, so it could be confusing), but there is still extension of the continental crust. The southern half of Arizona has part of the Basin & Range province, which stretches from Oregon to the south of Mexico. If you imagine ...


5

Short answer: yes, there are other mountains which contains oceanic crust in their lithologies. The process you described as "the upthrust of ocean crust" is called obduction. The resulting rock sequence is called an ophiolite. As you can see here, there is quite a lot of them around the world! One of the most studied is the Oman ophiolite. I have seen the ...


5

I want to add some nice examples of how divergent plate movement can actually create mountains, not destroy them. Here are two photographs I took several years ago from the Red Sea rift near Eilat, Israel: These mountains exist because of the plate movement. Divergent plate boundaries cause rifting, and the geomorphological expression of a rift is a valley. ...


4

Do divergent tectonic plates destroy mountains? The short answer is "no". Erosion destroys mountains. Period. Not slumping, not faulting, not "flowing back to flatness" in the absence of compression, not sticking to a wayward plate. Just plain old, basic erosion. To fully understand the physics of rocks and the processes that lead to mountain building, you'...


4

Mountains tend to fault and collapse back to flatter ground once the building forces cease. This is a very slow process and rarely leads to the complete elimination of a mountain range. So, left on their own, mountains tend to flatten, however, mountain ranges rarely completely disappear certainly not from these forces alone. Even the oldest mountain ranges ...


4

This may not answer your question to your liking but there is fairly relevant research on the topic. I think there is still a debate about the causes of the recent (Late Cenozoic) uplift, however. The current dominant theory relates the shallow subduction of the Farallon Plate to subcontinental delamination and increased bouyancy all the way to the Front ...


3

I think that notations S$_1$, S$_2$, ..., S$_n$ may well refer to any ordered orogenetic phases producing schistosity in any rock, anywhere, at any time Generally, yes. This is not only true for the Alps, but also for any other orogenic regions in the world (e.g. Himalayas, Arabian-Nubian Shield). Note that the numbering is ($n$) is used very loosely. ...


2

What exactly are you trying to measure? some of the great North American and Andean batholiths have cooling histories of at least 20 million years, and maybe more than 50 million years. It is perhaps inappropriate to think of the crystallization process as having a single date. Phenocrysts near the top of the pluton are cooler, but may sink to deeper levels ...


2

Compared to some other fields in geology, this one actually has immediate practical implications. By "knowing the history of mountains", you can learn a lot about processes that involve erosion, weathering, seismicity, etc. This is important for risk management and mitigation. Landslides and rockfalls are a significant risk in some countries. There are many ...


2

examples of mountain ranges with sedimentary or metamorphic cores Mount Everest. At an elevation of 7000 metres and higher, it is all sedimentary rock. Below 7000 metres, it is metamorphic of sedimentary protolith. There are some igneous intrusions into it, but the bulk is a metamorphic schist. https://en.wikipedia.org/wiki/Mount_Everest#Geology


1

Orogeny (the building of mountains) is the result of converging plates, but the composition of the resulting mountain range will vary depending on tectonic setting: Subduction The subduction of an oceanic plate under a continental plate will create a volcanic arc (such as the Andes). This is called an accretionary orogen. Partial melting of the mantle ...


1

The better site for sample collection would be the accessible site where it's possible to pick up a sample. Unless you have a drill rig or an excavator, you are limited to what's exposed. If you still have access to several zones of the pluton, take all of them. The more samples you have, the better it is. By choosing not to sample a certain zone you might ...


Only top voted, non community-wiki answers of a minimum length are eligible