Distinguishing between 'on' and 'above'?

Question

> 世界のルールで、島は水**より上に**出ていなければならないと決まっています。 > World rules determine that an island must stick out above the water. In this sentence 水より上 clearly means 'above the water', but when I look in bilingual dictionaries they just translate 'above' as 上. I wonder how this sentence would sound if より was omitted? Supposing I had the sentence: > 時計はテーブルの上にある。 Without further context would this be interpreted as "The clock is **on** the table" or "The clock is (on the wall) **above** the table"? Or is there ambiguity? Would the ambiguity be removed if I wrote 時計はテーブルより上にある to mean **above** the table? In summary, I'm just trying to understand the difference between の上に and より上に. Also, I wonder if より下 is used. There seems to be no need to distinguish between below and under.

Answer 1

より is probably acting as a mark of comparison. There is the water level, and then above and beyond that is the water. The island MUST stay above the water level no matter what.

And yes, 上 means above, on (top of), upon. There are some words like 真上, which seems to have a bit more of an "above" meaning (suspended from the ceiling, on a different floor/level) than an "on" meaning.

To be on a wall, I'd probably say 時計は黒板の真上に壁にかけています - The clock is (hanging) on the wall above the blackboard.