How do i make lavafalls that appear & dissapear?

I've been wondering how can i make 1...I can give you some examples:
Example 1:Red Volcano Zone.

Example 2:Magma Cavern Zone 2 by HyperKnux(Map showed in Chaos Twilight)

And example 3:Magma Core Zone by Blade T. Hedgehog(OLDC May/June)

Anyways...How do i make them?
And i want to know how to make them aslo with a FOF.

You could always just open the maps yourself, you know.

He can't open Red volcano zone though. The best way is to look at how the maps do it. I suspect that it can be done with a gargoyle box outside a map, though it could be just a linedef action just for this. I haven't tried anything like that yet.

It's a linedef. Can't be bothered to look at which one it is, though.

Linedef Type 88 + A water FOF with or without damage = The thing that i wanted to do. Thanks for your help, though.