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# Tidal Currents 1 

## Currents Tutorial

Tidal currents occur in conjunction with the rise and fall of the tide.  The vertical motion of the tides near the shore causes the water to  move horizontally, creating currents. When a tidal current moves toward  the land and away from the sea, it “floods.” When it moves toward the  sea away from the land, it “ebbs.” These tidal currents that ebb and  flood in opposite directions are called “rectilinear” or “reversing”  currents.

Rectilinear tidal currents, which typically are found in coastal rivers  and estuaries, experience a “slack water” period of no velocity as they  move from the ebbing to flooding stage, and vice versa. After a brief  slack period, which can range from seconds to several minutes and  generally coincides with high or low tide, the current switches  direction and increases in velocity.

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Tidal currents are the only type of current affected by the  interactions of the Earth, sun, and moon. The moon’s force is much  greater than that of the sun because it is 389 times closer to the  Earth than the sun is. Tidal currents, just like tides, are affected by  the different phases of the moon. When the moon is at full or new  phases, tidal current velocities are strong and are called “spring  currents.” When the moon is at first or third quarter phases, tidal  current velocities are weak and are called “neap currents.”

### Currents Lessons

              - Welcome
              - Tidal Currents 1
              - Tidal Currents 2
              Coastal Currents
              - Waves
              - Longshore Currents
              - Rip Currents
              - Upwelling
              Surface Ocean Currents
              - The Coriolis Effect
              - Surface Ocean Currents
              - Boundary Currents
              - The Ekman Spiral
              The Global Conveyor Belt
              - Thermohaline Circulation
              - The Global Conveyor Belt
              - Effects of Climate Change
              How Are Currents Measured?
              - Age of Exploration
              - What is a "knot"?
              - Shallow Water Drifter
              - Deep Ocean Drifter
              - Current Profiler
              - Shore-based Current Meters
              - How Currents Affect Our Lives?
              - References
              - Roadmap to Resources
              - Subject Review

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