block up vs close up

block up and close up both are verbs.

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

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

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

block up (verb)	close up (verb)
render unsuitable for passage	refuse to talk or stop talking; fall silent
	block passage through
	unite or bring into contact or bring together the edges of
	cease to operate or cause to cease operating

block up (adverb)	close up (adverb)
	very close