Tides are the rising and falling of ocean water caused by gravitational forces from the Moon and Sun. They occur in cycles called tidal stages including flood tide, high tide, ebb tide, and low tide. Tides can be semidiurnal, with two high and two low tides per day, or diurnal with one cycle per day. Ocean currents are directed flows of ocean water driven by forces like the Earth's rotation, wind, temperature/salinity differences, and lunar gravity. They transport heat and influence continental climates.

1. Tides and Currents
2:55 AM Author: Tomas U. Ganiron Jr 1

2. Tides
• are the cyclic rising and falling if Earth’s ocean surface
caused by the tidal forces of the Moon and the Sun
acting on the oceans. The changing tide produced at a
given location is the result of the changing positions of
the Moon and Sun relative to the Earth coupled with the
effects of the Earth’s rotation.
2:55 AM Author: Tomas U. Ganiron Jr 2

3. Intertidal zone
• Is the strip of seashore that is submerged at
high tide and exposed at low tide.
2:55 AM Author: Tomas U. Ganiron Jr 3

4. A tide is a repeated cycle of sea level changes in the
following stages:
• Over several hours the water rises or advances up a
beach in the flood tide.
• The water reaches its highest level and stops at high
tide. Because tidal currents cease this is also called slack
water or slack tide. The tide reverses direction and is
said to be turning.
• The sea level recedes or falls over several hours during
the ebb tide.
• The level stops falling at low tide. This point is also
described as slack or turning.
Tides may be semidiurnal (two high tides and two low tides
each day), or diurnal (one tidal cycle per day).
2:55 AM Author: Tomas U. Ganiron Jr 4

5. • The various frequencies of astronomical forcing which
contribute to tidal variations are called constituents.
Its period is about 12 hours and 24 minutes, exactly half
a tidal lunar day, the average time separating one lunar
zenith from the next, and thus the time required for the
Earth to rotate once relative to the Moon.
• The changing distance of the Moon from the Earth also
affects tide heights. When the Moon is at perigee the
range is increased and when it is at apogee the range is
reduced. Every 7½ lunations, perigee coincides with
either a new or full moon causing perigean tides with the
largest tidal range
2:55 AM Author: Tomas U. Ganiron Jr 5

6. Current
• A current, in a river or stream, is the flow of
water influenced by gravity as the water moves
downhill to reduce its potential energy. The
current varies spatially as well as temporally
within the stream, dependent upon the flow
volume of water, stream gradient, and channel
geometrics.
2:55 AM Author: Tomas U. Ganiron Jr 6

7. Ocean current
• is any more or less continuous, directed movement of
ocean water that flows in one of the Earth's oceans.
• Ocean Currents are rivers of hot or cold water within the
ocean. The currents are generated from the forces
acting upon the water like the earth's rotation, the wind,
the temperature and salinity differences and the
gravitation of the moon.
• Ocean currents can flow for thousands of kilometers.
They are very important in determining the climates of
the continents, especially those regions bordering on the
ocean.
2:55 AM Author: Tomas U. Ganiron Jr 7