Recent comments in /f/askscience

Mdork_universe t1_jdg0l0t wrote

Reply to With the extraordinary amount of precipitation that has fallen on California, would that weight have any effect on the tectonic plates/fault lines and could it cause a major earthquake? by barfly2780

Unlikely. Considering the enormous masses of the Pacific plate and the North American plate, the mass of the water on California is relatively tiny. Simplistically, earthquakes are the release of one plate being crushed into another. I know, the San Andreas is a transform boundary. I lived next to it most of my life in Southern California. It slides about as smoothly as a couple of pieces of coarse sandpaper rubbing together! They’re relatively easy in comparison! Remember Newton’s formula F=ma, where mass is both plates, acceleration is the distance roughly of a fingernail. F is is going to be some insanely huge number—small wonder earthquakes are so bad!

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xrelaht t1_jdfzwzx wrote

Reply to comment by canineraytube in Does the metal in the solid core of a rocky planet have any special properties? by VillagerNo4

I am not an expert, but my understanding is this is at least partially correct. As mentioned, asteroids are differentiated core fragments, and impact craters (eg Chicxulub) are sometimes dated by the iridium distribution in geological layers. The iridium comes from the asteroid. I don’t know why iridium gets all the press over other other platinum group elements, but a cursory search suggests they’re also used for impact dating. https://physicsworld.com/a/iridium-in-undersea-crater-confirms-asteroid-wiped-out-the-dinosaurs/

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DrQuinn79 t1_jdfzqsa wrote

Reply to With the extraordinary amount of precipitation that has fallen on California, would that weight have any effect on the tectonic plates/fault lines and could it cause a major earthquake? by barfly2780

Probably not. The water runoff, whether drainage or melt, will flow at a pretty evenly distributed rate. However, if it gets down into a particularly dry aquafer or subterranean reservoir, it might cause shifting in the ground due to saturation, but I doubt anything major would occur. I'd be more concerned about landslides and rockfalls, i.e. the removal of topsoil.

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notimeforniceties t1_jdfzfu5 wrote

Reply to comment by sciguy52 in Does the metal in the solid core of a rocky planet have any special properties? by VillagerNo4

Someone else can probably explain this properly, but I believe the fusion reaction inside the Sun ends up leaving it as all Iron. Something about the fusion reaction past a certain point can't produce elements higher than Iron on the period table.

Edit: https://www.ck12.org/flexi/chemistry/nuclear-fusion-in-chemistry/why-do-nuclear-fusion-reactions-stop-once-nickel-and-iron-are-formed-in-the-core-of-stars/

> When very massive stars leave the main sequence, they first become red supergiants and then end their life cycles in with a bang. Unlike a red giant, when all the helium in a red supergiant is gone, fusion continues. Lighter atoms fuse into heavier atoms up to iron atoms. Creating elements heavier than iron through fusion uses more energy than it produces so stars do not ordinarily form any heavier elements.

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CrustalTrudger t1_jdftxd5 wrote

Reply to comment by UnamedStreamNumber9 in Does the metal in the solid core of a rocky planet have any special properties? by VillagerNo4

Heat from radioactive decay (primarily of uranium, thorium, and potassium) is an important component of the internal heat budget. These elements are the most abundant in the crust, but they are also present in the mantle and given the size of the mantle, even at low concentrations, they end up generating significant heat.

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dukesdj t1_jdfsbqs wrote

Reply to comment by OlympusMons94 in Does the metal in the solid core of a rocky planet have any special properties? by VillagerNo4

> However, with evidence from the rock record of a dynamo for the past 3.5-4.2+ billion years, this leaves a long gap where it is more difficult to explain what drove the geodynamo.

Dynamo theory also suggests that the Earth has had a dynamo since its formation (in the impact process that formed the Moon). The reason being is that one can argue that in the present day the Earths dynamo is subcritical which essentially means it can maintain a strong field but not magnetize the core from a weak magnetization state. If this is correct and Earths dynamo is subcritical now then it is almost certainly subcritical throughout its life (since it was more rotationally constrained in the past, faster rotation) and so the dynamo must have existed since the formation of the Moon.

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