The sea caves are huge natural caves scoured out of the red sandstone and conglomerate cliffs by the ocean waves as the sea rises and falls with the
. It's actually resonance which causes the tides to be as high as they are, the Bay of Fundy being just the right size and shape as to create a resonance with the times of the rise and fall of the tides. The result is tides which, in certain areas of the bay, reach 50 feet in height when the sun and moon are positioned properly.
The rocks of St. Martins are Triassic in age, about 250 million years old, and belong to the Honeycomb Point, Quaco and Echo Cove formations. The large sea caves are in the red Honeycomb Point Formation. The coarse boulder conglomerate is part of the Quaco Formation. The contact of the two formations is easily seen at the east end of the beach in front of the restaurants. Very few fossils are found in these rocks. Nova Scotia's fossil history includes the oldest dinosaurs in North America found in Triassic age rocks. These rocks are too old to have dinosaurs.
St. Martins has beautiful examples of sea caves, shallow features carved into sandstone and conglomerate. Waves pound relentlessly on the coastal cliffs. Sea caves are caused by physical erosion, unlike chemical solution caves in karst landscapes where carbonate bedrock has been dissolved by natural acids in rain and groundwater. In sedimentary rocks like these the caves may form along rock layers. You can see this where the boulder conglomerate meets the red sandstone. The cave floor is on the same angle as the rock layers.
From a timeline at the caves
The Village's premier attraction is the St. Martins sea caves. Walkers and hikers consult the tidal charts to find the best time to walk the ocean floor out to sea caves, caverns and arches. The tide rises, soon erasing their footsteps, filling the caves and caverns with water. The tide rises and falls every 6 hours and 13 minutes , creating new times for high and low tides every day. The tidal range can be up to 38 feet on our shores in St. Martins.
The amount of water that flows in and out of the Bay of Fundy in a day is equal to all of the water pumped into all of the oceans by all of the rivers of the earth.
From St. Martins Sea Caves