Tidal bulge
Topic: Movements of Ocean Water: Waves, Tides and Currents · NCERT: Class 11, Ch 13 "Movements of Ocean Water"
Meaning
A tidal bulge is a heap of ocean water raised by the tide-generating force. That force is the difference between the Moon's pull and centrifugal force (the outward force that balances gravity). There are two bulges at the same time. One faces the Moon, where its pull is strongest. The other is on the far side, where the pull is weakest and centrifugal force wins. As the Earth turns, each place passes through both bulges, so it gets two high tides and two low tides. The full cycle takes about 24 hours 50 minutes, so high tide comes about 50 minutes later each day.
Example
Along most of India's coast, as at Kolkata port on the Hooghly, there are two high tides and two low tides a day. Large ships time their entry to the port for high tide.
Don't confuse with
- Tidal range: the difference in height between high and low water at one place. The bulge is the raised water itself.