Please read to the bottom of this page before attempting this EarthCache...you will need to stay in the area for about two hours, but don't worry, you can leave and go caching and come back two hours later.
The Moon's gravity pulls the oceans towards it. Even though the Moon is approximately 240,000 miles from the Earth, it is large enough that its force of gravity is strong enough to affect the tides here. Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of the Earth.
Tide tables, like the one found here for this area Biloxi, MS, Tide Chart, can be used for any given locale to find the predicted times and tidal range for an area. The predictions are influenced by many factors including the alignment of the Sun and Moon, the pattern of tides in the deep ocean, the shape of the coastline, and other factors. They are, however, only predictions...the actual time and height of the tide is affected by wind and atmospheric pressure as well. In this area along the Gulf of Mexico, we generally only have one high tide and one low tide each day, while areas bordering the major oceans usually have two high tides and two low tides each day. Our tide type is called diurnal (areas with two high and low tides each day are called semi-diurnal).
Tide changes proceed via two main stages:
- The water stops falling, reaching a local minimum called low tide.
- The water stops rising, reaching a local maximum called high tide.
Coastal Erosion
Coastal Erosion is the loss or displacement of land, or the long-term removal of sediment and rocks along the coastline due to the action of waves, currents, tides, wind-driven water, or impacts from storms, such as hurricanes.
The seawall built along Mississippi's Coastline from Pass Christian to Biloxi was purposely built to protect the roads along the coast from tidewater, and a Bill passed in 1924 authorized not only the erection of the seawall, but also breakwaters, bulkheads, sloping beach, or any other necessary device to protect and preserve roads, streets and highways affected by tidewater. The seawall you can see in this area was started in 1927, and completed by 1930. The "beach" was added years later. When it was originally constructed, the water from the Gulf of Mexico ran right up to the steps of the seawall.
The sandy beach you see in this area is part of the longest man-made beach in the world at 26Â miles long. The sand was first dredged from the Mississippi Sound in 1951 to create a 300-foot-wide beach across the entire coast of Harrison County. The main purpose of this beach was to add to the seawall built earlier to protect the roads along coast from tidewater. The beach creates another form of shore protection by stabilizing the shoreline, and it serves as a protective buffer against waves, high water, and major storms. Because the beach is man-made, and no sand naturally occurs along the Mississippi Coastline, more sand has to be dredged from the sound and added to the beach about once every decade.
The devastation along the coast from massive hurricanes such as Camille in 1969 and Katrina in 2005 could have done far more erosion damage along the coast if not for the man-made beach and seawall. The seawall here is also the longest and largest seawall in the world.
In addition to the man-made erosion-control devices in place here, the Mississippi Gulf Coast also has one major natural barrier from erosion damage from tidewater: the barrier islands. These islands help protect the shoreline from the type of constant wave energy that affects other areas without them.
To complete this EarthCache, you will need to accomplish the following:
Find something in the water you can use to measure the change in tide over a two-hour period (the nearby pier would be a good choice). Mark a spot where the tide is currently at, and measure the difference when you come back two hours later. If you don't want to get as wet, I would advise coming just after high tide so that your mark is above water when you come back, as the water will be falling during the time you are gone.
1. What time and day did you make your measurement? How much did the tide change in that two hour period?
2. How many high tides does this area experience each day? Why do you think that is?
3. Do you think the man-made seawall near this area along the north side of the beach helps to reduce erosion due to changes in the tide, storm surges, and wave action?
4. Do you think the material that the sewall is made out of is adequate to protect this area over a long period of time?
5. Do you think the man-made beach would protect the coastline here from erosion by itself without the addition of the seawall?
5. Required: Take a photo of you or your group near the educational moon sign at the posted coordinates. You do not have to show your face in the photo, but make sure something of yours is in the picture (GPS, phone, thumbs up, etc).
