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.
1 Put reflectors on your wheels and on the front and rear of your bike. 2  At night use a headlight and an active red light and reflector on the rear of your bike. 3  Maintain your bike: Carry a pump, a patch kit and a spare tube. 4  Take care of yourself: Carry plenty of drinking water and snacks for energy.arking. 1  You can park your bicycle on a sidewalk as long as it does not impede pedestrian traffic. 2  You can park your bicycle at the curb or edge of the roadway where parking is allowed as long as it does not obstruct other vehicles.