10.6 NOTES
What are the tides?
Objective: Describe what causes and affects the tides
Throughout the day, the water level of the ocean rises and falls. These regular
changes in ocean water levels are called tides. When the level rises and covers
part of the beach, it is called high tide. When it falls and leaves the beach
exposed, it is called low tide.
Tides are caused by the gravitational pull of the moon. The oceans are stretched
out creating two bulges of water on Earth. One side faces moon, and the other
directly opposite it. These are the high tides. The two areas between the high
tides are the low tides.
The tides change about every 6 hours and 15 minutes. Each quarter rotation of
Earth causes a major change in tides. Since a day is 24 hours long, a quarter (or ¼)
of the day is 6 hours. Therefore, we have 2 high tides and 2 low tides every day.
A high tide is also called a flood tide, or incoming tide. An outgoing tide, or low
tide, is called an ebb tide.