Lecture Notes on Tides by Dr. Rob Brander

Introduction

• Speaker: Dr. Rob Brander, Surf Scientist, University of New South Wales
• Topic: Different type of wave - the tide

Understanding Tides

• Definition of Tides:
  • Tides are a type of wave.
  • High tide = crest, Low tide = trough.
  • Occur daily: Water moves up and down the beach.

Characteristics of Tides

• Timing Changes Daily:
  • High tide today differs from high tide tomorrow.
• Tidal Range:
  • The vertical elevation difference between high tide and low tide changes daily.

Forces Behind Tides

• Gravitational Influence:
  • The Moon exerts gravitational force on the Earth, causing water to bulge towards it.
  • Earth rotates, leading to two tidal bulges experienced daily (i.e., two high tides and two low tides).

Timing of High/Low Tides

• Earth's Rotation vs. Moon's Orbit:
  • Earth rotates at a certain speed; Moon orbits at a different speed.
  • There is a 50-minute lag between high (and low) tides each day due to this difference.

Tidal Variations

• Spring and Neap Tides:
  • Spring Tides: Occur when the Sun and Moon align, creating larger tidal bulges.
  • Neap Tides: Happen when the Moon and Sun are at right angles, leading to smaller tides.
  • Cycle: Every two weeks, alternating between spring and neap tides.

King Tides

• Definition:
  • King tide = larger spring tide.
  • Occur biannually when the Moon and Sun are close to the Earth.
  • Not a sudden surge of water; totally predictable and not dangerous.

Conclusion

• Overview of tides and their characteristics provided.
• Upcoming episode will focus on different types of beaches and their behaviors.