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scrappyisachamp t1_j3xeerc wrote

Reply to comment by Bob_Skywalker in Why are coastlines crinkly near the poles but smooth in the tropics? by emsot

Is the weathering “heavier” in the tropics or have the coastlines just had longer to smooth out? Glacial periods near the poles are somewhat frequent on geologic timescales, so the water there hasn’t had as much time to erode the coastlines compared to the tropics, but the erosion “rate” is probably similar between the two regions, no?

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Past-Willingness-207 t1_j3xs563 wrote

Weathering definitely happens at different speeds, depending on the type and intensity of weathering. There mainly are 3 types:

  • physical (water and wind move sand and small rocks around, they become smaller through friction; material reacts to temperature differences by extending/shrinking, making way for water to intrude through cracks; also water then potentially freezing, extending and breaking rocks)

  • chemical (water reacts with minerals, resulting in the emergence of more or less potent acids)

  • biochemical (mainly driven by organic acids, created by decaying organisms, root secretions, huminic acids)

These three interact with each other. Weathering intensity is highest near the equator, because of basically all the life that's happening there. Great biodiversity + heavy precipitation year round means lots of fuel for weathering.

Interestingly, there's also the concept of relief energy - weathering in great heights happens quicker simply because of the greater potential/gravitational energy.

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newaccountscreen t1_j3xh30b wrote

Frost wedging has a large impact in the poles, water melts gets into cracks, freezes and then expands causing more fractures to be infilled and cracked. The erosion rate between the tropics and the poles is probably close by I imagine the tropics have more erosion present. I'll be back to update this comment when I can read up more. Source, also a b.s in geology

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