Answer:
The crust is thinner and less dense than the mantle.
The correct answer is stabilizing selection.
Stabilizing selection is a kind of natural selection in which the mean of the population steadies on a specific non-extreme trait value. This is considered to be the most general process of action for natural selection as the majority of the traits do not seem to vary radically with time.
Stabilizing selection is the reverse of disruptive selection. In spite of preferring individuals with extreme phenotypes, it favors the transitional variants. Stabilizing selection seems to eradicate the more extreme phenotypes, resulting in the reproductive success of the average or norm phenotypes.
This signifies that the most general phenotype in the population is chosen and continues to govern in the coming generations. As the majority of the traits vary slightly with time, stabilizing selection is considered to be the most usual kind of selection in the majority of the populations.
Because these volcanic activities happen on plate tectonics.
This is not the best answer but I hope it could help you.
