Baja, Mexico
February 28-March 1, 1998

We went rather far afield this time, to explore the northern parts of the Baja peninsula. The primary destination was to view algal mats in coastal lagoons there. Algal mats are thought to be one of the ways that life first formed, a community of microbes. We also tried to look for Ammonite fossils that signaled the end of the Cretaceous and others that came in during the Tertiary--in between, of course, would be a K/T boundary. We followed the Arizona and California state lines the first day, visiting the Salton Sea and camping in Anza Borrego State Park. The second day, we headed into Mexico and followed GPS coordinates to the Ammonite fossil spot, but got stuck in the mud for the evening. We beachcombed for fossils and investigated the algal mats on day three, then headed home on day four.

Thanks to David Trilling, Joe Spitale, Eric Wegryn, Peter Lanagan, Cynthia Phillips, and Barb Cohen for pictures!

Salton Sea group at Salton Sea
The Salton Sea (above left) is a shallow inland lake formed by the diversion of the Colorado River into a low-lying area of southeastern California. Joe (above right) gives us the history and geology of the area: the Salton Sea filled up and evaporated periodically throughout history, as the Colorado River delta silted up and caused the river to seek other drainage routes. In the early 1900's, the area was a playa with a town built on it when the river started flowing into it again. The present Salton Sea is what remains of that last flooding cycle, presumably with the town remains on its floor. Only evaporation is occurring now, and river engineering will prevent the area from filling again.

at the waterfront After seeing the Salton Sea from above, we went down to the waterfront. Because it has no outlet, continued evaporation causes the water to become hypersaline. The waterfront is full of dead fish and is quite stinky.

We spent a beautiful night in Anza Borrego State Park, CA (below), where we discussed the tectonic history of the Baja peninsula. Cynthia and Josh (right) brough a laptop to the campfire to show some really cool animations of colliding and subducting plates. Anza Borrego State Park
campfire talk

desert pavement Even our lunch stops were educational. We saw well-developed desert pavement at an I-8 rest stop near Yuma (left). Wildflowers were spectacular because of the El Nino rains, and Pete (right) discussed the nature and evolution of the plant life on the peninsula. field of flowers

The Trans-Peninsular Mountains (below) run down the western coast of Baja, and were formed in the same way as coastal California's mountains: as the Farallon plate subducted underneath the North American plate, melting and volcanism occured inland, close to the boundary. These volcanoes and plutons form a chain along the coast.
trans-peninsular mountains

vans in mud Pacific sunset
We traveled as far south as San Antonio del Mar, a coastal area south of Ensenada. We had GPS coordinates of the stops courtesy of the CalTech field trip group, and tried to follow them, but shortly before sunset we traveled over a boggy area and two vans got stuck in the mud. As we tried to extricate them (above left), the vans who made it thorough the muddy area enjoyed a Pacific sunset (above right). We got free of the mud at about 1 a.m. and made camp near the beach. The next day, we explored the beach (below left) for gastropods and ammonites, and the K/T boundary between them. Despite being rather unsuccessful in this venture, we did learn a lot about fossils and impacts, and we also had a good time at the beach (below right).
Ammonite beach group at beach

David and algal mat Later on day three, we went a little further south to Laguna Negro, where there are abundant algal mat colonies. The algal mat style of living, with many different kinds of microbes interdepent on one another, is thought to be the oldest way of living on the earth. When algal mats die and are fossilized, they are known as stromatolites. David (left) examines a chunk of the algal mat that Jay dug up. The mats form in shallow, saline lagoons, like below. The next morning, we used a small microscope to examine the mat structure and organisms (right). Betty with microscope
view of algal mat

Because of the mud delay, we spent day four just trying to get home. We went by way of San Felipe to see the Colorado River delta and then up to Arizona again. But we did manage to stop for some of Baja's legendary fish tacos (below). Yum! fish tacos

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Last Modified: April 30, 1998