Subduction Zone
Veteran Member
Weathering depends upon a lot more than "hardness". In crystallography hardness only measures resistance of a mineral to being scratched. There are other factors to consider. Toughness, or how well it resists fracturing is important. And there are numerous ways to measure that. But when it comes to sedimentary rock the key factor is how well indurated, or cemented it is. Limestones tend to be very well indurated. Though any sedimentary rock will have a range in values. But of all of them limestone is one of the toughest. Sandstone can vary from very soft. Where I grew up you would take a shovel to outcrops of St. Peter Sandstone if you wanted a sample but that too can be extremely well cemented. Shale generally is one of the softest of rocks.I think I clearly stated it.
Amount of erosion....or lack of.
Also the range’s make up
Everest has much soft rock, like marble & limestone: 3.5 - 4 on Moh’s scale. Weathering would show faster results on Everest, than say a range with more granite.
And yet, we see little erosion, not millions of years..
This thread is about a different set of evidence. Not gonna get sidetracked anymore.
Good night.
If you see a sedimentary rock cliff it is quite often limestone, and a bit less often sandstone. And very rarely shale. That has far more to do with how difficult it is to erode than hardness. Calcite is a three on the Moh' s hardness scale. Quartz is a seven. If you bet which one would resist erosion better based only on hardness you would lose far more often than you would win.