What is a TOMBOLO?
It may be defined as “a beach connecting an island to a mainland".
How is a Tombolo formed?
Beach and nearshore processes interact in the coastal environment and as a result characteristic sedimentary forms may be developed. The Tombolo is unique in that it is subject to interaction of waves from two directions and to varying degrees, depending on the state of the tide.
A Tombolo relies on wave interaction effectively producing two beach faces and therefore subjected to processes from two directions. It’s development is complex but in its simplest form it is initiated in a deep-water wave sheltered area behind an obstruction, such as an island, where wave fronts refract and interact from two directions. These waves meet and cancel the sediment (sand) transporting ability of one another. The sand is deposited and building commences either from the island to mainland or from the mainland outwards. The Tombolo is complete when the spit of sand connects to the obstruction. In our case Burgh Island is connected to the mainland by the sand tombolo.
How is the Bigbury Beach Tombolo formed?
Immediately to the west of the coast at Bigbury-on –Sea, BURGH Island provides the necessary obstruction and refraction of deep-water Atlantic waves. In simplistic terms these waves are divided by the island and bend around into the relatively `still` area near the mainland. They then collide from the south and north enabling any sand to be deposited and hence the formation of the connecting beach or Tombolo. Deposition of sand on the south side is further enhanced by the flow of tidal water from the mouth of the River Avon.
What affect does man have on the Bigbury Beach Tombolo?
The 26 acre Burgh Island is home to the Burgh Island Hotel, the Pilchard Inn (Public House) and several small dwellings. This means that the tombolo needs to be crossed both on foot and by vehicle. During low tide it can be crossed by four-wheel drive vehicles but at high tide a special machine known as the ‘Sea Tractor’ can be seen travelling between the island and the mainland. This hydraulically operated machine can negotiate the tombolo at most high tides with passengers riding safely above the waves. Obviously, any machine travelling over the sand will have an affect on sand compaction and movement.
PARKING, ACCESSIBILTY & DOGS!:
Parking is available next to the earthcache in the South Hams District Council Car Park. There is a charge and Charges apply at ALL TIMES so don't get caught without a ticket! You can bring your 'geohound' but you can only take them on designated parts of the beach. Signs showing which areas are located around the car park and slipway.
PLEASE NOTE: I CANNOT ACCEPT JOINT ANSWERS FROM GROUPS OF GEOCACHERS AS I DON'T HAVE THE TIME TO SORT OUT WHO HAS SENT WHAT FOR WHOM!. IF YOU WANT TO LOG MY EARTHCACHE PLEASE EXTEND ME THE COURTESY OF MESSENGING ME YOUR OWN ANSWERS INDIVIDUALLY. THANK YOU
TO LOG THIS EARTHCACHE YOU MUST ANSWER SOME SIMPLE QUESTIONS ABOUT THE TOMBOLO .
1. At LOW TIDE walk across the Tombolo from the mainland slipway to the Burgh Island slipway (next to the Pilchard Inn). USING YOUR GPS FOR THE CALCULATION, ESTIMATE THE LENGTH OF THE TOMBOLO IN MILES, FEET OR METRES.
2. HAVING WALKED ACROSS THE TOMBOLO STATE, IN YOUR OPINION, WHICH END OF THE TOMBOLO IS THE HIGHEST AND WHICH IS THE LOWEST?
3. GIVE A REASON WHY THE TOMBOLO SHOULD BE HIGHER AT ONE END THAN AT THE OTHER?
4. WALKING BACK TO THE MAINLAND LOOK AT THE SAND GRAIN SIZE. IN YOUR OPINION STATE WHICH END OF THE TOMBOLO HAS FINER (smaller) SAND AND WHICH END HAS COARSER (Bigger) SAND GRAINS?
5. GIVE A REASON WHY THE GRAIN SIZE MIGHT BE DIFFERENT?
As a bonus but not a logging requirement for the earthcache, please add a photo if you can as the views are spectacular.
YOU MUST LOG AT THE SAME TIME AS SENDING ME YOUR ANSWERS VIA A GEOCACHING MESSAGE. If you can`t do both at the same time then wait until you can, otherwise I will just delete your LOG and you will have to do it all again as I DO NOT have the time to chase after you. AND be warned, I do check every one! Unfortunately, a few geocacher`s try to log the earthcache without completing the task and so I will maintain the right as the earthcache owner to delete any logs that do not fulfill the requirements or I entries that I believe to be false. I will ONLY contact you if there is a problem AND I will delete any logs for which I don`t receive answers or LOGS that I believe to be false..
Thanks and enjoy this wonderful location.
SNAKE PLISSKEN -