Islas San Pedro Martir and San Esteban, Baja California, México
We spent a fulfilling morning exploring the volcanic island of San Pedro Martir. It apparently formed during the late Pliocene Epoch as an indirect result of rifting and plate separation in the center of the Sea of Cortez. Today, however, the island is heavily eroded and mostly covered with a thick layer of guano laid down by countless generations of sea birds (see photo). Long before we reached the island, we encountered masses of blue-footed and brown boobies, brown pelicans, magnificent frigatebirds, red-billed tropicbirds, Brandt’s cormorants, and Heermann’s and yellow-footed gulls making their way there ahead of us. Upon arrival, we first circumnavigated the island with the ship, and found a nice anchorage site near the southern end. Conditions were perfect for exploring the coastline with our Zodiacs, so we quickly put them down and gave everyone a chance to get up close and personal with the myriad birds on the boulders and slopes near the water. Most of the Zodiac drivers went completely around the island, poking into caves, driving through cuts, and circling within bays. In addition to the birds, we encountered lots of sea lions. Most of them paid us no mind, but the youngsters came out to the boats to chase us and cavort around us…to the screams of delight by many of the guests. The birds have been here a long, long time and have hidden most of the surface of the island with their droppings. So much so, that the island once provided important nitrate for the fertilizer industry. We could see various stoneworks put up in years past by Indians and Mexican workers who did the back-breaking work of collecting the nasty stuff. Nowadays, it is a nature reserve that requires a special scientific permit to even land on it. We could clearly see that what isn't hidden by the thick covering of guano is obviously the remains of a compound volcano composed of many layers of ash. Erosion has long since broken down the structure considerably, exposing the massive tuff stone formation. One can easily see various layers in the sedimented ash deposits, which included many small boulders of solid basalt, indicating several explosive eruptions through the ages. There are also plenty of guano-dusted cardon cacti growing high up on the slopes and on the top-most level, and we couldn’t help but wonder how these plants can survive in the presence of all this nitrogenous waste.
We made an afternoon landing on nearby Isla San Esteban and had a chance to walk up an arroyo, or river wash, and enjoy pleasant conditions among what some would consider a ‘lush desert.’ It was surprising to some among us to encounter such a plethora of green plants, many with blossoms, so beautifully adapted to these extreme conditions. The cardon cacti are enormous, bigger and more impressive than one might have suspected while simply viewing them from offshore on board the ship. We could also see lots of evidence of the fauna, especially large lizards known as pinto chuckwallas, but few species showed themselves while we were there among them. This day certainly proved a great introduction to the rich and varied islands of the Sea of Cortez and their fascinating natural history.
We spent a fulfilling morning exploring the volcanic island of San Pedro Martir. It apparently formed during the late Pliocene Epoch as an indirect result of rifting and plate separation in the center of the Sea of Cortez. Today, however, the island is heavily eroded and mostly covered with a thick layer of guano laid down by countless generations of sea birds (see photo). Long before we reached the island, we encountered masses of blue-footed and brown boobies, brown pelicans, magnificent frigatebirds, red-billed tropicbirds, Brandt’s cormorants, and Heermann’s and yellow-footed gulls making their way there ahead of us. Upon arrival, we first circumnavigated the island with the ship, and found a nice anchorage site near the southern end. Conditions were perfect for exploring the coastline with our Zodiacs, so we quickly put them down and gave everyone a chance to get up close and personal with the myriad birds on the boulders and slopes near the water. Most of the Zodiac drivers went completely around the island, poking into caves, driving through cuts, and circling within bays. In addition to the birds, we encountered lots of sea lions. Most of them paid us no mind, but the youngsters came out to the boats to chase us and cavort around us…to the screams of delight by many of the guests. The birds have been here a long, long time and have hidden most of the surface of the island with their droppings. So much so, that the island once provided important nitrate for the fertilizer industry. We could see various stoneworks put up in years past by Indians and Mexican workers who did the back-breaking work of collecting the nasty stuff. Nowadays, it is a nature reserve that requires a special scientific permit to even land on it. We could clearly see that what isn't hidden by the thick covering of guano is obviously the remains of a compound volcano composed of many layers of ash. Erosion has long since broken down the structure considerably, exposing the massive tuff stone formation. One can easily see various layers in the sedimented ash deposits, which included many small boulders of solid basalt, indicating several explosive eruptions through the ages. There are also plenty of guano-dusted cardon cacti growing high up on the slopes and on the top-most level, and we couldn’t help but wonder how these plants can survive in the presence of all this nitrogenous waste.
We made an afternoon landing on nearby Isla San Esteban and had a chance to walk up an arroyo, or river wash, and enjoy pleasant conditions among what some would consider a ‘lush desert.’ It was surprising to some among us to encounter such a plethora of green plants, many with blossoms, so beautifully adapted to these extreme conditions. The cardon cacti are enormous, bigger and more impressive than one might have suspected while simply viewing them from offshore on board the ship. We could also see lots of evidence of the fauna, especially large lizards known as pinto chuckwallas, but few species showed themselves while we were there among them. This day certainly proved a great introduction to the rich and varied islands of the Sea of Cortez and their fascinating natural history.
