Schematic of the lunar portion of earths tides showing (exaggerated) high tides at the sublunar and antipodal points for the hypothetical case of an ocean of constant depth with no land. There would also be smaller, superimposed bulges on the sides facing toward and away from the sun.In Maine (U.S.) low tide occurs roughly at moonrise and high tide with a high moon, corresponding to the simple gravity model of two tidal bulges; at most places however, moon and tides have a phase shift.English: Tides schematic. Due to the bathymetry of some areas, neap and spring tides reach their maximum force 2 days after the first quarter moon, third quarter moon and new moon, full moon, respectively. In the absence of complications due to bathymetry, spring tides are exactly at the full and new moons and neap tides are exactly at the one-quarter and three-quarter moon. Every six hours the water also lowers or heightens; as such four tides are created: Low water spring tideHigh water spring tideLow water neap tideHigh water neap tideDate6 October 2009SourcePublic domain image: File:Tides schematic.JPG which was based on an image in Leidraad voor het Stuurbrevet by Richard Vooren, Paul Van den KeybusEnglish: Tides are the rise and fall of sea levels caused by the combined effects of gravitational forces exerted by the Moon, Sun, and rotation of the Earth. The semi-diurnal range (the difference in height between high and low waters over about half a day) varies in a two-week cycle. Approximately twice a month, around new moon and full moon when the Sun, Moon, and Earth form a line (a condition known as syzygy8), the tidal force due to the sun reinforces that due to the Moon. The tides range is then at its maximum; this is called the spring tide. It is not named after the season, but, like that word, derives from the meaning jump, burst forth, rise, as in a natural spring.When the Moon is at first quarter or third quarter, the sun and Moon are separated by 90 when viewed from the Earth, and the solar tidal force partially cancels the Moons. At these points in the lunar cycle, the tides range is at its minimum; this is called the neap tide, or neaps (a word of uncertain origin).English: Approximately twice a month, around new moon when the Sun, Moon, and Earth form a line (a condition known as syzygy8), the tidal force due to the sun reinforces that due to the MoonEnglish: When the Moon is at first quarter, the sun and Moon are separated by 90 when viewed from the Earth, and the solar tidal force partially cancels the Moons. At these points in the lunar cycle, the tides range is at its minimum; this is called the neap tide, or neaps (a word of uncertain origin).English: Approximately twice a month, around full moon when the Sun, Moon, and Earth form a line (a condition known as syzygy8), the tidal force due to the sun reinforces that due to the MoonEnglish: When the Moon is at third quarter, the sun and Moon are separated by 90 when viewed from the Earth, and the solar tidal force partially cancels the Moons. At these points in the lunar cycle, the tides range is at its minimum; this is called the neap tide, or neaps (a word of uncertain origin).The M2 tidal constituent. Amplitude is indicated by color, and the white lines are cotidal differing by 1 hour. The curved arcs around the amphidromic points show the direction of the tides, each indicating a synchronized 6-hour period. Tidal ranges generally increase with increasing distance from amphidromic points. The colors indicate where tides are most extreme (highest highs, lowest lows), with blues being least extreme. In almost a dozen places on this map the lines converge. Notice how at each of these places the surrounding color is blue, indicating little or no tide. These convergent areas are called amphidromic points. Tide waves move around these points, generally counterclockwise in the N. Hemisphere and clockwise in the S. Hemisphere 1617English: The M2 tidal constituent. Amplitude is indicated by color, and the white lines are cotidal differing by 1 hr. The curved arcs around the amphidromic points show the direction of the tides, each indicating a synchronized 6 hour period.Deutsch: Gezeiten als in den Weltmeeren umlaufende Wellen. Die Amplitude der Pegelschwankungen ist farbkodiert. Es gibt mehrere Knotenpunkte verschwindender Amplitude, um die die Wellen herumschwappen. Linien gleicher Phase (wei) umgeben die Knotenpunkte bschelfrmig. Die Wellenausbreitung erfolgt senkrecht zu diesen Linien. Die Richtung ist durch Pfeile angedeutet.R. Ray, TOPEX/Poseidon: Revealing Hidden Tidal Energy, GSFC, NASA. Redistribute with credit to R. Ray, andNASA - Goddard Space Flight CenterNASA - Jet Propulsion LaboratoryScientific Visualization StudioTelevision Production NASA-TV/GSFCThe lunar gravity differential field at the Earths surface is known as the tide-generating force. This is the primary mechanism that drives tidal action and explains two equipotential tidal bulges, accounting for two daily high waters.English: Differential gravity field that causes tides.English: A schematic showing the diurnal, semidiurnal and mixed types. The image was made by Michael Pidwirny of the Irving K. Barber School of Arts and Sciences, University of British Columbia, Okanagan /fundamentals/8r.htmlEnglish: A schematic of the water surface level changes with the tides. Average low water spring or average low water neap tide; used as a reference, which one is used depends on whether LWN or LWS is lowest. The schematic was hand drawn based on an image from the book Leidraad voor het Stuurbrevet by Richard Vooren, Paul Van den Keybus. Note that the ALWS/ALWN is best replaced by LAT (lowest astronomical tide) in a next version of the image. As this water level may be lower than ALWN/ALWS, some of the text will be rendered obsoleteDownload original file818 517 px pngOriginal file - 0 0 pxOriginal file - 818 517 pxSmall - 220 139 pxMedium - 640 404 pxLarge - 0 0 pxView in browserYou need to attribute the authorShow me howYou need to attribute the authorPlainHTMLYou have enabled Media Viewer for all filesNext time you click on a thumbnail on Wikipedia, Media Viewer will be used.You have disabled Media ViewerNext time you click on a thumbnail on Wikipedia, you will directly view all file details.Media Viewer is now disabledEnable Media Viewer?Enable this media viewing feature for all files by default.Learn moreEnable Media ViewerCancelDisable Media Viewer?Skip this viewing feature for all files.You can enable