Ebb tide continues for 6 hours 13 min. Also goes on for 6 hours 13 min. Again, high tide. Two such cycles take about 25 hours. Tides move enormous amount of water four times every day, yet the topographic effect of tides on coastal zone is small because of their relatively low speeds.
Tidal currents are capable of erosion.
Thus bays are slowly turned into mud flats, then marshes. Finally, tides are not equally well developed along all coastlines. Waves Waves are generated by the friction of air blowing across the water surface. Thus the energy of waves comes from wind. Waves are vertical motions of molecules of water, carrying energy from one place to another as a wave spreads.