Conversation so far:
what does the movement of air masses cause
A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena outside the tropics.
how are the weather fronts depicted
In surface weather analyses, fronts are depicted using various colored triangles and half-circles, depending on the type of front.

Question: how do the separated masses differ
Self-contained rewrite: how do the separated air masses differ