I see the world in layers: layers of people, experience, emotion, and inspiration. That's appropriate, since I'm an archaeologist in my "day job" at the University of Illinois: http://www.itarp.uiuc.edu/atam/aboutatam/wisseman.html
My other job is mystery writing. Gradually I'm excavating my own life to unearth situations and characters that will make good mysteries. Creepy old attic museums--digs in Israel, Italy, and Nevada--peculiar academic characters who become murderers (or murderees!).
Like an archaeological dig, a good mystery is constructed in layers: the top layer, or stratum, is what the reader sees and where the main story takes place. A couple of strata down is where the villain hangs out, plotting and planning away, occasionally rising to the surface like a misplaced artifact in an ancient garbage pit.
Garbage pits definitely loom large in an archaeologist's life because stratigraphy is rarely orderly. People in the past were always digging holes to lay a foundation trench, bury something (or someone), or to hide some garbage before constructing a new floor.
Personalities have layers too, and it's the job of writers to reveal the layers in their characters in ways that move the story along. And everyone has a garbage pit--the family traumas from the past, the dysfunctional relationships of the present. Garbage, like compost, can provide rich beginnings for new stories.
Archaeological stratigraphy is disrupted by tree roots and animal tunnels as well as human activity. A writer's ideas are like busy moles, pushing up from the depths to reveal new evidence and old treasures.
As I grow older, my life is ever more layered. I am grateful for such complexity, as it will feed my writing as long as I can hold a pencil or type on a computer.
Causes Sarah Wisseman Supports
Archaeological Institute of America