Transcript Tides
Tides tida_NOAA.gif Purpose: Explain tides and the relationship with the Earth, Sun and Moon Classify different types of tides Identify hazards associated with tides New Terms Tides Tidal range Spring tides Neap tides Storm surge Ocean Tides The daily movement of ocean water that changes the level of the ocean’s surface Tides are caused by 1.The gravitational attraction of the moon 2. “centrifugal force” as Earth and the moon orbit around a common center of balance The Earth and Moon orbit around the “barycenter” (demonstration) High Tides are bulges of ocean water that occur on the side of the Earth facing the moon and on the side opposite Low Tides are the areas between the bulges. Tides change as the Earth rotates between the bulges Tides occur 50 minutes later each day. Since the moon moves along in its orbit around the earth each day, the earth must rotate an additional 50 minutes to catch up. Spring Tides Have a very large tidal range Occur every 14 days during a full or new moon Sun Spring Tides Sun Moon Moon Are caused by the gravitational forces of the sun and moon pulling in the same directions (180 degrees) Neap Tides Have small tidal ranges between high and low tides Occur every 14 days during 1st and 3rd quarter moons Neap Tides PHASESofMoon.JPG Sun Sun Moon Moon Are caused by the gravitational forces of the sun and moon pulling at 90 degrees from each other Tidal Range is the difference in height between the high tide and low tide. At low tide in the Bay of Fundy, boats can be left setting on the bay bottom. High tide arrives in 30 minutes in the Bay of Fundy, rising 20-50 feet Tides of Nova Scotia The Bay of Fundy is in Canada near northeastern USA The Bay of Fundy is known for tidal bores. A tidal bore is the “face’ or edge of the incoming tide and travels about 13 mph. Surfing a tidal Bore " When hurricanes or winter storms arrive during high tide, greater damage occurs. Storm surges result when strong winds pile water along the shoreline. Storm surges may raise sea level up to 18 feet above normal. During Hurricane Andrew, an oceangoing tugboat was left high and dry by storm surge. Along the Florida Keys, houses are built on stilts as a protection from storm surges.