Tides and Moon Phases
Overview
This lecture explains the roles of the sun and moon in creating tides, focusing on special tide types—spring tides and neap tides—and their relationship to moon phases.
Gravity and Tides
- The moon creates tides on Earth through its gravitational pull.
- The sun exerts a stronger gravitational force on Earth than the moon, but its effect on tides is weaker.
- The moon affects tides more because it is closer, leading to a larger difference in gravitational pull across the Earth.
Sun and Moon Alignment Effects
- The sun and moon sometimes align to create unusually high or low tides.
- When both the moon and sun pull in the same direction, they reinforce each other’s tidal effects.
Spring Tides
- Spring tides occur when the sun and moon are aligned (new moon and full moon).
- During spring tides, high tides are higher and low tides are lower than usual.
- Spring tides happen twice per lunar cycle (every new moon and full moon).
- The term "spring" here means "to spring up," not the season.
Neap Tides
- Neap tides occur when the sun and moon are at right angles relative to the Earth (first and third quarter moons).
- During neap tides, high tides are lower and low tides are higher than usual (tides are weaker).
- Neap tides also happen twice per lunar cycle (first and third quarter moons).
Moon Phases and Tides
- New moon and full moon phases lead to spring tides (strongest tides).
- First and third quarter moon phases lead to neap tides (weakest tides).
Examples and Biological Impact
- Some animals, like turtles, use knowledge of spring tides and moon phases to access food more easily during extra-low tides.
Key Terms & Definitions
- Spring Tide — A tide with especially high high tides and low low tides, occurring during new and full moons.
- Neap Tide — A weak tide with lower high tides and higher low tides, occurring during first and third quarter moons.
- Lunar Cycle — The sequence of phases the moon goes through as it orbits Earth.
Action Items / Next Steps
- Review the phases of the moon and how they relate to spring and neap tides.
- Be able to identify when spring and neap tides occur during the lunar cycle.
- Homework: Find examples of animals whose behaviors are influenced by tidal patterns.