Parallax Background

Start scrolling

This would be section one

Here is where you can talk about a whole bunch of things

You'd then scroll to see section two and that can talk about something else and get this revealing effect.
Maybe go with a colour set of ombre or background images to get the desired effect.
The background can also be a fixed parallax background and not move as you scroll up which is a different effect to the previous. However, only one slide could ever have this affect
And this would also work for mobile which is good but we have to make sure background and text isn't taller than the smallest screen