Intrusion

Once upon a time, deep under ground, the lighter colored stone developed a crack or two... as, it seems, they always do. Later there was an event that injected some magma into said cracks filling them neatly and precisely. A few million years later the original block of stone was uplifted to the surface and eroded back down to expose this nice zig-zag pattern. And all of this just for your viewing pleasure!

Sierra Nevada
Rock
Intrusion
Crack