4

There is a paper about this in the Bulletin of Volcanology (Hetényi et al. 2012). Cooling rate seems to be the main parameter controlling column size (faster cooling yielding to thinner columns). According to the authors, cooling rate is itself controlled by two non-independent factors: (1) the geometry of the lava body, and (2) the chemical composition of ...


3

Yes, there are many differences and subdifferences and nuances. I will try to keep it in simple terms which will satisfy your question. Alkaline magmas form by low degree partial melting of the deep mantle. This is why you see them in hotspots. It's very hot down there, but you do not form a lot of melt. For example, the amounts of melts in Hawaii are ...


2

Diabase is indeed relatively erosion resistant. One of the reasons is grain size. Consider the two other chemical equivalent of diabase: gabbro (coarse-grained) and basalt (glassy and fine-grained), which should potentially be similarly erosion resistant. This is not the case. Both gabbro and basalt erode very easily. Coarse-grained rocks, in general, ...


2

Molten rock must be a liquid, mobile rock is any rock capable of moving, sand and mud can be mobile.


1

I believe the author's was referring to phenomena like salt diapirs (where mobile salt deposits intrude into heavier overlying sediments). These produce low hills in the gulf coast region of the United States. The salt that is moving is not liquid, it is merely mobile. I do not believe the author of the book you reference was referring to sand and mud ...


1

The podcast may have given the impression that sediment always gets buried or pushed down into the earth. This isnt the reality of the processes which are dynamic and dependent on geologic time as well as where these process can or can't happen. It really depends on the location and the processes happing there.


1

The rocks are undoubtedly of volcanic origin, and I would attribute the marks on their surfaces to shrinkage while their interiors were still in a semi-molten condition but rapidly cooling. The white crystals are probably quartz.


1

The first department that comes to mind is obviously academia, i.e. faculty or research positions at universities. However, there are many other career paths available (hopefully: there are not enough academic positions for every student completing a Ph.D...). For volcanologists, there is actually a nice site called volcanologists outside academia. As the ...


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