It is deep because unfathomed means we don’t know where it ends. If it was shallow, we would know how deep it was easily.
It makes them upset because it tells them of many negative and upsetting events.
He was content because he did not see solitude as a bad thing or his enemy.
It was always there. Being perennial, it was of a long duration.
He would criticize the position. It doesn’t make sense to ascribe morality to nature.
They are more likely to party too hard. They tend to be extravagant and wasteful.