A crevasse is a deep crack, or fracture, found in an ice sheet or glacier, as opposed to a crevice that forms in rock. Crevasses form as a result of the movement and resulting stress associated with the shear stress generated when two semi-rigid pieces above a plastic substrate have different rates of movement. The resulting intensity of the shear stress causes a breakage along the faces.
Unfortunately, many cyclists choose to ride their bikes at dark without bicycle head lights or tail lights. This is against the law in most states in the U.S. (Amazingly, Washington, Texas, and others only require a head light and rear reflector.) It is also very dangerous.here are at least two primary reasons for you, a bicycle rider, to use lights at night. 1  First, the front head light illuminates the area in front of you, so you can ride safely, by being able to detect any hazards you approach.
Exceptions include Ride with lamps and reflectors on at night and in dim light. (169.222, subd. 6) â¢Only ride a bicycle with working brakes. (169.222, subd. 6 b) â¢ Donât ride a bicycle if its size doesnât allow the operator to stop, support and restart bike safely.xceptions include Ride with lamps and reflectors on at night and in dim light. (169.222, subd. 6) â¢Only ride a bicycle with working brakes. (169.222, subd. 6 b) â¢ Donât ride a bicycle if its size doesnât allow the operator to stop, support and restart bike safely.