3D Mask for a 3D Animated Object

This is for some low-fi Hololens development work I'm having trouble with. I have a miniature topographical mesh that I want to place as a square object on a desk. I want to have the ability to scroll through the landscape to look at different areas, while keeping its footprint static. It's basically a cropped, unmoving 3D window of a larger animated topography.

Imagine animating the topography below in a single direction while keeping the view confined to the box it's in. I'm very new to Unity, but I'm assuming this would be some sort of 3D mask or clipping plane I'd apply to the object. I've searched all over the web but can't find any relevant answers. Any pointers or advice would be very appreciated!