# Tag Info

## Hot answers tagged tectonics

18

Starting from the bottom of your question I would not compare planets with plate tectonics with planets that don't have this process. During rifting of a tectonic plate a triple junction will be the most favourable way of faulting the crust. After that two arms of the rift are favoured and the third one becomes a failed rift (aulacogen). Because of this ...

15

Most probably, he was referring to the Brunswick Magnetic Anomaly: http://www.geosociety.org/news/pr/2014/14-22.htm This is an area of lower-than-normal magnetism present in North America in the Southwestern United States. Note that altough it COULD be a piece of Africa, it could also be caused by something else.

14

Found an article that used a simple analytical modelling to determine how high a mountain can be. Reference Based on simple physics, tallest a mountain will be on Earth is ~10 km. This is based on: Simple cone shape for the mountain. Vol ≈ $r^2 h$ Based on weight of the mountain: Weight W ≈ $\rho g r^2 h$ Stress σ the mountain exerts on the ground ...

11

The glacial buzzsaw hypothesis (summary; sample paper) is that mountains can't get much higher than the elevation at which glaciers form cirques. The upper walls of the cirques are steep and erode easily, which planes off the peaks above them, shortening the mountains. The evidence is, to summarize, that they don't get much higher than the cirques. Cirques ...

10

Yes. In fact there are already volcanos associated with the San Andreas fault system. Neenach is an extinct Miocene volcano split in half by the San Andreas fault. Garry Hayes wrote a nice blog post about this volcano system: A Volcano Sundered: A Field Trip Along the San Andreas Fault. If you'll allow some latitude in what counts as 'a San Andreas ...

10

New Zealand sits along an oblique convergent plate boundary, where the Pacific and Australia Plates meet. The boundary between the two plates is shown in your second figure as the grey line, with the Pacific Plate to the east and the Australia Plate to the west of it. In terms of relative movement, we can think of the Australia Plate as being stationary and ...

10

It is a continent-continent collision following subduction, no subduction is taking place at the moment. The ocean floor that was attached to it has vanished into the mantle or got wedged into the thickened crust. The collision builds up immense stress, resulting in deformation, faulting, folding, crustal shortening and uplift of the Tibetan plateau. https://...

9

Scientific GPS and SLR have been used for some time now, and the measurements are rather accurate. Not only do we measure horizontal movements of tectonic plates, but also uplift as e.g. in the Tibetan and Colorado plateaus. Before the GPS was introduced, paleomagnetism were used in some studies to estimate the velocities; The age of oceanic crust are ...

9

The Himalayas are indeed rising, but they are also being eroded at a comparable rate. It will come as no surprise to anyone that the maximum possible height of a mountain on Earth is only marginally higher than Mt Everest, that is probably about 9000 to 10,000 metres high. There are, of course compressive / convergent plate boundaries where there is a ...

7

A fault is a crack in the rock that shows movement over time. The movement may have stopped (eg. small faults seen in the field in the UK) or be essentially dead even though the crack still represents a weakness that occasionally shows a small amount of movement (e.g. the Great Glen Fault in Scotland). Yes it is often possible to map a fault in 3d by ...

7

The tiger stripes of Enceladus are thought to be a result of this moon's unusual chemical composition, as opposed to any mineral heterogeneity or thermodynamic perturbations occurring due to the phase change near the rocky core. Ammonia has been found indirectly to exist on Enceladus and the unique ammonia-water composition of Enceladus is thought to give ...

7

The fact that these three features are parallel may be somewhat coincidental, although we can suspect that tectonic forces have influenced their morphology. The crust under the Arctic Sea is one of the least understood regimes in the world. This is changing - whichever country can prove that their nation's continental shelf extends along one or more of ...

7

It's a huge field of research and a lot of interesting studies have been published over the years, but also a lot of speculation. Models and theories are mostly based on surface structures observed by remote sensing. Potential field data, as gravimetry can also add good constraints when available. Tectonic forces might be rather common in large young ...

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

If you have no prior information that event B depends on event A, it's a logical error to claim event A causes event B just because you find they are correlated. Let's say you collect a large data set of how people use their computer-mouse, and show that there is some change in a statistic of this data preceding an earthquake. That cannot not prove that the ...

5

I don't find Ide et al's recent paper to be very convincing. They only studied three earthquakes - hardly a statistically representative sample. There are millions of earthquakes on record, and hundreds of really big ones, of more than about MM 7.0, so there is plenty of scope for a more rigorous study. They occur at all phases of the tides. Some have ...

5

The effects one can see on other planets (and many of the icy moons in the solar system) are typically faults and scarps due to the fact that during cooling, these bodies contracted. Since the surface was solid, the only way to accommodate the contraction is through faults. But Earth's surface is not solid on long time scales. We have plates that move, ...

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. ...

5

The subducting plate never really melt. It just gets recycled into the mantle (the Asthenosphere to be more precise), which is in solid state. It is plastic and deformable enough to allow convection flows, but it is solid. Beside more mantle, something that forms from the subducting plate is magma. The water contained in the subducted slab (that was once ...

5

The example of the East African Rift was given in a different answer. Splitting of mountain ranges in two becomes even more apparent as you go up north from there. The Red Sea between Egypt and Saudi Arabia is a young new spreading ocean, that cuts through Precambrian mountains. Further north from there, the Dead Sea is a combined transform–rift zone ...

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

It's an interesting thought. Antarctica is not so balanced as it might appear on the maps. East Antarctica is old, consisting probably of cratons and Proterozoic orogenic domains whiles West Antarctica is much younger, thinner and have mostly been accreted during the formation of Gondwana (See e.g Boger 2011). If there was a direct control of the location ...

4

To clarify: Your question is valid, although if you are referring to Dr. von Frese's words as paraphrased in this article, you may be conflating a potential "breakup initiation" with something like the "creation of a geologically weak area prone to rifting under extensional stress". I believe the thought that such a crater could have caused the beginnings ...

4

Divergent boundaries are going to form where the crust is weak and thin, a divergent boundary siis very unlikely to form in an existing mountain range. Imagine trying to pull apart a lumpy cookie, is it going to break through the thick lumps or the thin areas. That's not saying a rift could not cut across a mountain range but it will be very unlikely, it ...

3

The structures are not mature or well defined and deformation was thought to be diffused, i.e., distributed over a large area. Earthquakes such as the M8.6 2012 Indian Ocean earthquake (largest strike-slip earthquake on record) appear to accommodate some, if not all, of the deformation. Seafloor geodesy is relatively a new field. Most studies are limited ...

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