Due to the combined gravitational effects of the Sun and Moon, extreme tidal ranges occur twice a month at the 2 times when the Sun, Moon, and Earth are lined up. However, when the Sun, Earth, and Moon are at 90 degree angles, smaller tidal ranges occur, called neap tides. Students will better understand that Spring and Neap tide are based on the tidal ranges and not just the level of the water at low and high tide through this tactile graphic and active model.
- tide - daily changes in the level of ocean water
- high tide - water level higher than average sea level
- low tide - water level lower than average sea level
- tidal range - difference between the level of ocean water at high tide and low tide
- tidal cycles - the periodic changes in the intensity of tides caused primarily by the varying relations between the Earth, Moon, and Sun.
- spring tide - greatest tidal range which occurs two times a month, at the new moon and full moon
- neap tide - tide of minimum range which occurs at the first and third quarters of the Moon.