User:Lfstevens/Tide
From Wikipedia, the free encyclopedia
Tides are the rise and fall of sealevel that display a period of approximately 12 hours. The tide results from the changing relative positions of the Earth, Moon and Sun, coupled with the effects of Earth rotation and the shape of the near-shore bottom.[1][2][3]
Tide prediction is important for coastal navigation (see Navigation). The intertidal zone, the strip of seashore that high tide submerges and low tide exposes is an important ecological product of ocean tides (see Intertidal ecology).
Beyond the ocean, tidal phenomena can occur in other systems including the solid parts of the Earth, whenever a gravitational field that varies in time and space is present.
Short-term sea-level fluctuations, especially in shallow seas and near coasts, are not solely caused by astronomical tidal forcing, but are subject to forces such as wind and barometric pressure changes, resulting in storm surges.
Most coastal areas experience two daily high (and two low) tides. This is because at the point right "under" the Moon (the sub-lunar point), the water is closer to the Moon than the solid Earth; so it experiences stronger gravity and rises. On the opposite side, the antipodal point, the water is farther from the moon than the solid earth, so it is pulled lessāthe Earth moves more toward the Moon than the water doesācausing that water to "rise" as well. In between, the force on the water is diagonal to the sub-lunar/antipodeal axis, resulting in low tide.[4]