Layers function to express overlapping bits of information at the same time. This can be done visually like in the way a map can show the terrain of an area, the roads, and borders. Layers can also be done temporally through audio, video, and animation.
The process of layering in digital technology is derived from the mechanical process of printing. When printing was first being developed, each layer had a different element where it would come together in the final print as one image. In Lynda Barry’s graphic novel What It Is, her entire book is done in a collage style. She uses the physical cutting and pasting to layer cut out words and often random images like on page 15 in her novel. Here she mixes media (handwritten letters and drawings as well as cut out typed words, phrases, and sentences). The effect is not only intense detail but a kind of depth. At first glance everything appears messy and disorganized yet when you take time to look at each of the separate parts, together they give meaning to the overall message.
Another graphic novel I plan on reading, Mimi and the Wolves: Act I “The Dream” by Alabaster, makes use of layering as well. In this example on page 19, sound effects and speech bubbles are layered over the images to give meaning to the images as well as move the story along. The first half of the page is one thread of the story where one of the characters is focusing his attention on reinforcing a windmill in preparation for a tornado that may or may not come along in the future. The bottom half is another thread where the other characters build on the previous frames, talking about how he should focus his efforts in planting more food while they can.