1. Tides are caused by the moon’s gravity

2. The pull of the moon causes ocean water to bulge Oceans are attracted to the moon by its gravity. The pull of the gravity causes the seas waters to pull onto or away from the shores. This is the high and low tide we see at the shore.

4. On the Brittany and Normandy coasts of France, the tides are extreme as a result of the shape of the continental shelf.

5. Here the tide is so extreme the ships float at high tide and do this at low

6. The Fortress and Monastery of Mont St. Michel Example: The Fortress and Monastery of Mont St. Michel the Normandy-Brittany border on the Atlantic Coast of France

7. Mont St. Michel was built to use the tides as part of its defense system.

8. When the tide is low, you can walk from the mainland to the fortress.

9. Mont St. Michel at low tide. My kids, walking at low tide.

11. But when it is high tide, the fortress is surrounded by 15 feet of water. Help!