Ocean Waves Capillary Gravity Wind generated Tides Tsunamis Seiches

Tides

New Moon Full Moon First Quarter Third Quarter Lunar Phases

Moon’s faster orbits about the Earth, compared to Earth’s orbit about the Sun, means that “Spring” and “Neap” tides are defined by the Lunar orbit.

New Moon Full Moon Spring Tides occur when the lunar and solar gravitational pulls add up

First Quarter Third Quarter Neap Tides occur when lunar and solar gravitational pulls are mutually perpendicular

Tides can be SPRING and NEAP, depending on the relative positions of Sun and Moon SPRING and NEAP, depending on the relative positions of Sun and Moon DIURNAL, SEMIDIURNAL or MIXED, depending on their daily cycles DIURNAL, SEMIDIURNAL or MIXED, depending on their daily cycles

Wave interference can be constructive or destructive

Constructive interference Destructive interference

A B C

Tides can be 1. Diurnal: or once daily 2. Semidiurnal or twice daily and 3. Mixed

Semidiurnal tides are more common than diurnal and mixed tides

An amphidromic point is a point within a tidal system where the tidal range is almost zero, i.e., there is almost no vertical move-ment. Such points occur because of the coriolis effect and interference within oceanic basins and bays creating a wave pattern which rotates around the amphidromic point. These points are located at Tahiti, off the coast of Newfoundland, near the South Shetlands, tidal rangecoriolis effectinterferenceoceanic basinsbays TahitiNewfoundlandSouthShetlands midway between Rio de Janeiro and Angola, at three points in the North Sea and at several other locations in the Pacific, Atlantic and Indian oceans. The island of Madagascar is an amphidromic point, as is New Zealand. Rio de JaneiroAngolaNorth Sea Atlantic Indian MadagascarNew Zealand

Tsunamis

The travel-path of the tsunami of April 1, 1946

Active ocean- continent margins should expect tsunamis more frequently than the passive ones

The map below shows the position of the leading wave of a tsunami generated by a 1979 earthquake offshore Colombia, South America*. These contours are for the tsunami arrival times in hours. *K. Ida & T. Iwasaki (Ed.): Tsunamis: Their Science and Engineering (D. Reidel, Boston MA, 1983)

Consider an earthquake with its epicenter at Honolulu, Hawaii. The corresponding tsunami travel times (in hours) from Hawaii are given in this map of the Pacific Ocean.

No matter where an earthquake occurs in the Pacific, Hawaii is barely 15 hours away, at the most!

The Dec 2004 Asian Tsunami: The Dec 2004 Indian Ocean tsunami was produced by perhaps the strongest earthquake of the past 100 years. It occurred in the Java trench, off Bandar Aceh in north- western Sumatra. This animation was produced by the National Oceanic and Atmospheric AdministrationNational Oceanic and Atmospheric Administration