When the Sun, the Earth and the Moon are in a straight line, the resulting very high tides are called:

Spring tides occur when the Sun, the Earth and the Moon are nearly in a straight line. The gravitational pulls of the Sun and the Moon then combine, producing higher-than-usual high tides and lower-than-usual low tides.

When spring tides occur:

• They happen twice a month, on new moon days and full moon days.
• At new moon, the Sun and Moon are on the same side of the Earth (conjunction).
• At full moon, they are on opposite sides (opposition).
• In both cases, their tidal effects add up.

The name "spring" has nothing to do with the season. It comes from the idea of the water "springing up" or rising.

Neap tides:

• When the Sun and the Moon are at right angles to each other relative to the Earth, around the first and last quarter phases of the Moon, their pulls partly cancel.
• This produces neap tides, in which the difference between high and low tide is smallest.
• Neap tides also occur twice a month, about seven days after spring tides.

What causes tides:

• Tides are caused mainly by the gravitational pull of the Moon, and to a smaller extent the Sun.
• Although the Sun is much more massive, it is much farther away, so its tide-raising force is less than half that of the Moon.

Perigean spring tides:

When a spring tide occurs while the Moon is closest to the Earth (at perigee), the tides are even higher. These are called perigean spring tides or "king tides".

Importance of tides: they help ships enter and leave harbours, clean coastal waters and can be used to generate electricity.

Why not the other options?

• ✗Neap tides are the weakest tides, when the Sun and Moon are at right angles.
• ✗Good to know
• ✗Ebb tide is the falling or outgoing tide.
• ✗A rip tide (rip current) is a strong, narrow current flowing away from the shore.