Punta Santa Rosa to Arroyo Verde, April 3rd 2007.

We spent another easy day meandering down the coastline. This section has many points with coves between them. We made the trip longer by following the coast into these coves when the shore was rocky and interesting. Doug Hamilton and I spent a lot of time finding paths through the rocky reefs.

These reefs were yellow in color from the barnacles that covered them. They were flat on top and had a shelf with the water extending underneath them. The flat top was just below the high tide line and the bottom of the shelf just above the low tide. I developed a theory about how these reefs were formed. I knew that reef-building coral were rare in the Sea of Cortez and only existed farther south at Cabo Pulmo. So how to explain these reefs everywhere up here? I theorized that the barnacles only grow in a narrow band between the high and low tide. There they protect the soft rock from the erosion of the waves. The waves wear the rock away below the low tide and above the high tide. As the rock erodes down to the high tide line the barnacles cover it up and protect it from further erosion. The result is wide flat reefs just under the high tide line.

Once I came up with this theory I was able to find more evidence to support it. Many of the reefs had a lump, sometimes a tower, of rock in the very middle of them. This was evidence of a larger rock that had been eroded away. Eventually even the lump in the middle would erode away and the typical flat rocky reef would be all that remained. I also vaguely recall hearing about a barnacle that produces an acid that speeds up the erosion of rock. Presumably this acid cannot erode the rock where it is already protected by the barnacle itself. This would be an evolutionary adaptation that speeds up the formation of reefs with more surface area for more barnacles to grow on. So these are made not by an organism that grows reefs, but by an organism that carves reefs out of larger rocks.

After our lunch break we rounded Punta Santa Teresa and started heading directly south. Herb Howe was feeling poorly (a head cold he thought). He told me he would move slowly and catch up later. Andrea Wolf said she would hang back with him. I lead the rest of us at a stiff pace to get as far down this stretch as possible before stopping to camp for the evening. Don Fleming and Doug had not heard Herb’s message and thought that I was ignoring a growing problem of our group getting spread out. I told Kate DesLauriers to tell Doug to tell Don that Herb had a cold and was expected to go slow. Like a game of “Postman” the message mutated from person to person until I was apparently irresponsible for paddling away from a sick companion who was likely to pass out, fall into the water and drown at any moment. Don hung back to save Herb and then forgave me later when he heard the real story.

I rounded one last point to look into a large cove and discovered that we had made good progress and were at a community called San Sebastian or Arroyo Verde on the topo maps. There I saw all kinds of civilization strewn across the beach: recreational kayaks, jet skis and other motorboats. Behind the beach was a row of palm trees, sma, an impressive hotel-like building and many smaller structures. I turned back to meet everyone else at the last good beach before this place.

Despite seeking out a more remote place to camp, we still found signs of civilization in the form of tire tracks on the sand. After dinner Don and Andrea followed the tracks to a road and followed that for a while. The assumption was that the road would lead to the hotel I saw which would sell them drinking water and perhaps a margarita or two. Unfortunately, the road did not go around the point to the next cove but meandered out into the desert. Eventually our scouts gave up and came back to camp.

All text and images Copyright © 2007 by Mike Higgins / contact