This is the first in a series of photos of the passing of the tidal bore in Truro, Nova Scotia. The tidal bore is a tidal wave. Not the kind of wave generated by an earthquake, that's a tsunami. The tidal bore is literally a wave of sea water that rushes into areas such as tidal flats and coastal riverine systems when the high tide comes in. In the river in these photos, the water normally passes from the forground in the lower right away from the camera; we're looking downstream. When the tide comes in, the advancing sea water comes into the confined space of the river in the form of a wave. These photos show the passage of the wave and the change in the river that the tide brings. This shot is a 'before' pic. Note the low sand bar in the middle of the river in the middle distance. To its left is a small area of rapidly flowing water (I won't go as far as to call it a rapids). To its right is a higher bank that is currently being eroded by the river. Note that the top of the far bank is flat, bare mud. This suggests that it will be covered by water when the tide comes in.