What is the semantic difference between 積む{つむ} and 載せる{のせる} when loading stuff


My flashcard deck has 2 very similar cards:  
積む{つむ}

  * meaning: to load, pile up 
  * jisho.org: to pile up; to stack 

載せる{のせる}

  * meaning: to place on, load onto, draufstellen
  * jisho.org: to place on (something), to load (luggage); to carry; to take on board

As a non-native of either English or Japanese, I don't see the difference. I
feel like 積む is for big objects and a rough action, while with 載せる the loader
is concerned about the final position of a rather small object. But I have too
little evidence.  
So when I put an object on another object, when would I use the first and when
the second?




As Japanese native:

積む feels like many things are loaded, and also feels that they are put on top
of another (and I suppose that's what pile-up means).

載せる feels like putting something on top of certain base.

