block up vs obstruct

block up and obstruct both are verbs.

Word	Noun	Adjective	Verb	Adverb
block up	No	No	Yes	No
obstruct	No	No	Yes	No

As verbs, obstruct is a hypernym of block up; that is, obstruct is a word with a broader meaning than block up:

Other hypernyms of block up include block, close up, impede, jam, obturate, occlude.

block up (verb)	obstruct (verb)
render unsuitable for passage	block passage through
	shut out from view or get in the way so as to hide from sight
	hinder or prevent the progress or accomplishment of