Does Block prevent escape for the whole battle or just for one turn?

Does it work, say, on an Abra`s Teleport?

Say, if I want to catch an Abra, will it prevent its escape for the whole battle, will it prevent its escape for one turn or it won`t prevent its escape at all?

I would try it out on my own. But the price to learn it is 2000. And it takes a while to make that much. And the second reason is that I can`t even find an Abra. Night time on route 24 and I have 6-8 in-game hours (accumulated) trying to find it and only found one, which escaped.

--Moved to proper place--