upper layer

• surfaceOutermost boundary layer
• topUppermost part or surface
• crustHard outer layer
• skinBody's outer layer
• atmosphereGaseous layer around planets

stratosphere · canopy · ceiling · coating · veneer · overlay · mantle · film · sheath · covering · outer · above · frosting · glaze · membrane · epidermis · rooftop · blanket

• depth levelssurface, shallow, deep, bottom, underground