2. The pattern of positive and negative magnetic anomalies in the Elrond Sea can be correlated with the pattern of normal and reversed magnetism on the magnetic polarity time scale. Based on this correlation, how many millions years (m. y.) ago did sea floor spreading begin in the Elrond Sea

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me