Dynamic Planet B/C

[knottingpurple]

Could someone clarify the use of the Gutenberg Discontinuity for me? I thought it was used to define the core mantle boundary, but this article (https://en.wikipedia.org/wiki/Lithosphe ... e_boundary) says it is also close to the lithosphere asthenosphere boundary. These two (Core mantle and lithosphere asthenosphere) do not appear to be near one another at all, unless I am missing something here.

In Google results for Gutenberg discontinuity there are also some results talking about something at like 100 km depth and some at the base of the mantle, and reputable journal articles about both so I don't think it's a mistake, and there's definitely no way these things are the same, so I think it's probably 2 different things with the same name. That's true of the Lehmann discontinuity so I wouldn't be shocked if that's true of another discontinuity.

[appleshake123]

Could someone clarify the use of the Gutenberg Discontinuity for me? I thought it was used to define the core mantle boundary, but this article (https://en.wikipedia.org/wiki/Lithosphe ... e_boundary) says it is also close to the lithosphere asthenosphere boundary. These two (Core mantle and lithosphere asthenosphere) do not appear to be near one another at all, unless I am missing something here.

In Google results for Gutenberg discontinuity there are also some results talking about something at like 100 km depth and some at the base of the mantle, and reputable journal articles about both so I don't think it's a mistake, and there's definitely no way these things are the same, so I think it's probably 2 different things with the same name. That's true of the Lehmann discontinuity so I wouldn't be shocked if that's true of another discontinuity.

I came across similar things. According to Penn State, Gutenburg found the D'' Layers(Known as the Gutenburg Discontinuity Core-Mantle Boundary). The other boundary is the Gutenburg Low Velocity Zone(which is the LAB mentioned. This low velocity zone is the section where the lithosphere "rides" the asthenosphere and due to the relative flexibility of the asthenosphere, waves decrease in velocity but s-waves significantly decrease in velocity.

In comparison, Lehmann discoveries, as mentioned by knottingpurple, are the Lehmann Discontinuity inner-outer core boundary(During a large New Zealand earthquake, she found it because seismographs across the world obtained p-wave readings showing that not all waves were deflected like previously thought) and Lehmann Discontinuity in the mantle is found in primarily continental and island arc regions where, at 220 km depth, seismic wave suddenly increase in velocity(7% but more recent studies show 2-4.5%). It is within the lower end of the Low Velocity Zone of Gutenburg. Here's another source.

For anyone curious for a summary of the process, various attempts have been made to propose a reason for this increase in velocity. The hypothesis of mineralogical and chemical transition does not increase the velocity as drastically as observed. The current probable explanation is that "it represents the transition in deformation mechanism from dislocation to diffusion creep (Karato, 1992)." The anisotropic lithosphere quickly changes to a isotropic asthenosphere.

[OrigamiPlanet]

You might also want to look into the Mohorovicic Discontinuity, since that I believe separates crust and mantle from each other.

[jonathanzhang53]

so it says that you need to research mitigation of natural disasters caused by plate tectonics. but isnt the whole point of the disaster is the fact that it's "natural"

How do you mitigate something that can happen at any time. Even if you knew when it would happen, how would you stop it?

eg. tsunami, earthquake, volcanic eruption

does the cheat sheet mean precautionary techniques?

[knottingpurple]

so it says that you need to research mitigation of natural disasters caused by plate tectonics. but isnt the whole point of the disaster is the fact that it's "natural"

How do you mitigate something that can happen at any time. Even if you knew when it would happen, how would you stop it?

eg. tsunami, earthquake, volcanic eruption

does the cheat sheet mean precautionary techniques?

Isn't mitigation reducing the negative effects of an event, not necessarily removing the negative event itself? In that case, mitigation of natural disasters wouldn't be preventing natural disasters, but limiting the loss of life through appropriate construction techniques, etc.

Hurricanes are the example I can think of best off the top of my head, they're not relevant to tectonics but as an example of mitigation of natural disasters, you could build houses on stilts, so that when there's a storm surge it doesn't wash away the houses or flood them inside, since there isn't any direct way to prevent the hurricane from happening and having a storm surge.

It should be the same idea for the tectonics natural disasters - given that earthquakes and volcanoes and tsunamis are going to happen, mitigation means asking what can we do to make sure as few people as possible die when they happen, or there's as little property damage as possible, and so on? So there are ways of constructing buildings that are less likely to collapse in an earthquake, and things like that, I think that's what they're asking about. I guess that would be, as you say, precautionary techniques.

[appleshake123]

so it says that you need to research mitigation of natural disasters caused by plate tectonics. but isnt the whole point of the disaster is the fact that it's "natural"

How do you mitigate something that can happen at any time. Even if you knew when it would happen, how would you stop it?

eg. tsunami, earthquake, volcanic eruption

does the cheat sheet mean precautionary techniques?

An example of a building construction could be the Tuned Mass Damper. Taipei 101 is the common example.

[fffurious]

Are there any resources (e.g textbooks, websites) you guys would recommend for competitive C division? I rented Plate Tectonics by Frisch but it costs like $60 to buy, so I need some other options.

[appleshake123]

Are there any resources (e.g textbooks, websites) you guys would recommend for competitive C division? I rented Plate Tectonics by Frisch but it costs like $60 to buy, so I need some other options.

The appeal of textbooks is that everything is in one place; however, I personally wouldn't want to spend more than $20 on an event in science olympiad. I know many universities and colleges have amazing articles about various topics. Tulane has a easy to find and broad range of geology-related information which are free, but there are also many other university pages like harvard, columbia, penn state, and maryland that have papers relating to geology and general topic.. What I enjoyed doing is searching for information about one section then if I come across a new topic within that section, I would diverge and continue to branch out as long as it is withing the possible Dynamic Planet spectrum.

[skiski]

Hello! Can someone possibly help me determine the meaning of letter F: "Continental drifts role on opening and closure of ocean gateways/ land bridges, with specific reference to ocean circulation changes, climate change, and biotic migrations"? I took some notes on the land bridge theory, but I'm completely lost on everything else. What do I search up to find information on this topic?
Thanks in advance!

[knottingpurple]

Hello! Can someone possibly help me determine the meaning of letter F: "Continental drifts role on opening and closure of ocean gateways/ land bridges, with specific reference to ocean circulation changes, climate change, and biotic migrations"? I took some notes on the land bridge theory, but I'm completely lost on everything else. What do I search up to find information on this topic?
Thanks in advance!

I can remember people being weirded out by that bit last year as well, I think part of it might be the ability of the West Wind Drift to circulate after the other continents separated from Antarctica, and another bit is talking about speciation as a result of physical separation of species, but I haven't yet found any good sources on this bit.