Erosion of earth covers used in shallow land burial at Los Alamos, New Mexico

A keyboard input device includes an elastic spring member bonded to a overcoat provided on a film substrate by an adhesive so that a movable contact part provided in the elastic spring member is disposed over a pair of fixed contact parts provided on the film substrate. An air-passage hole is provided on the ceiling of the elastic spring member including the movable contact part, the air-passage hole being disposed in the vertical moving direction of the movable contact part. Grooves are provided in a key-top at a portion thereof to be in contact with the top of the elastic spring member, the air-passage grooves being formed in a direction perpendicular to the axis of the air-passage hole to communicate with the air-passage hole. The air in the hollow elastic spring member is discharged, when the key-top is pressed to deform the elastic spring member, to the outside of the elastic spring member through the air-passage hole and the air-passage grooves.