March 14, 2011
From the anchorage at Puerto Villamil two volcanoes dominated the horizon. To the west was the distant dome of Volcan Cerro Azul but immediately to the north loomed the massive shield volcano, Sierra Negra. The latter was not the tallest volcano in the Galapagos (that distinction went to the younger Volcan Wolf at the north end of Isabela) but it was the most massive in volume. The active volcanoes on the Big Island of Hawaii are also shield volcanoes and these contrast in their gently rounded, upwardly convex, domes from the classic shape of composite volcanoes such as Japan’s Mount Fuji which are steeper-sided and upwardly concave.
Having admired Sierra Negra every day for two weeks, we were aware that much of the time the top was obscured by clouds and heavy rain was falling somewhere between it and the coast. Usually the peak was clearest in the early morning with the clouds building up during the day but we knew that it would be a matter of chance as to how the visibility would be on the Monday that we had booked our tour with guide, Julio. As we prepared to leave the boats to meet him at 7 am at the dock, things looked encouraging and we were indeed very lucky to have a beautiful clear morning.
Marina was feeling better and up to the rigorous hike but sadly John had now succumbed to the virus and decided to stay onboard the hospital ship. Julio met us with two pick-up trucks in which we would ride for about 45 minutes to the start of the trail. Our departure was slightly delayed because when we arrived at the dinghy dock with Adrian and Jackie, a large sea lion was blocking the boardwalk to the shore. Initially it moved inland ahead of us but when it realized that it could not get off the walkway it became less friendly and we did not have room to sneak past without risking a nasty nip. Finally, Randall did his best impression of the Pied-Piper and, using his walking stick, he managed to encourage the sea lion to follow him back to the dock where it happily flopped into the water while we could proceed ashore.
On the way to the mountain we picked up two other hikers, Gail and Todd, who were sight-seeing for a few days by ferry from the sail-boat “One World” which was anchored (with crew aboard) at Isla San Cristóbal. The drive started on the main, paved road that Randall and I had ridden our bikes along and took us through the agricultural area of Isla Isabela in which we could mostly see fruit trees of various types (guava, bananas, mangoes, etc.) The last part of the ride was on a dirt road which was quite steep and eroded in spots. We were passing more interesting vegetation at this point, including some endemic tree ferns.
Jackie (in the other truck from Randall and me) spotted a vermillion flycatcher on a fence which made me very envious as I had great hopes of seeing this distinctive red bird that is an endemic subspecies found only in the higher areas of the Galapagos. Despite searching for it all day and on the drive back, I never saw one but was almost fooled by some scarlet hibiscus flowers passing by at 30 mph. The bird life in general was not particularly memorable from this day but this was more than compensated for by the scenery.
The trucks left us at the top of the road by a National Park campground and having driven up most of the ascent, we set off towards the east on a wide, gently sloping path. The total walk was more than 10 miles (16 km) with little shade and Julio kept us going at a fairly steady pace so this tour was no idle stroll. While Julio pointed out some of the endemic plants, there did not seem to be time to stop and take photos and notes of them all so we were a bit embarrassed on our return to not remember whether or not one shrub Julio had pointed out was thin-leafed Darwin’s shrub (Darwiniothamnus tenufolius). We knew that it had “Darwin” in the name but that did not narrow the options down as much as one might think. According to our “Darwin in Galapagos” book, there are at least 24 taxa of plants and animals and 5 geological features in the Galapagos that include “Darwin” somewhere in their name.
Unfortunately, the plants that made the most impression on us were the non-native, invasive species, particularly the shrubs of guava. These were so widespread and dominant in the vegetation on the side of Sierra Negra that it would take a huge effort to remove them all to allow the native vegetation to flourish. Two other widespread invasive plants on the islands were also purposely introduced; hill blackberry for its fruit and as a living fence and red quinine for malaria medication. Huge projects to control these latter species using precisely placed herbicides have been initiated on other islands and in the case of the blackberry a biological control program has been considered. The guava shrubs were so widespread on Isabela that the removal or treatment of individual plants looked overwhelming. However, it seemed unlikely that biocontrol would be considered for a plant that is widely grown for its fruit in the island’s adjacent agricultural area.
As interesting as the vegetation was to us and how impressive the views were back towards the coast, these were soon forgotten as the path crossed the lip of the volcano and we found ourselves overlooking the massive caldera of Sierra Negra. (Calderas are greater than 1 mile or 1.6 km across, craters are smaller.) This is the second largest caldera in the world with a rim circumference of 20 miles (32 km) and diameter of more than 6 miles (10 km). It is not particularly deep, 500 ft (150 m) from the lip to the surface of the lava, especially compared to the caldera of the volcano on neighboring Isla Fernandina which is 3000 ft (900 m) deep. However, despite this great size, Julio showed us that it was still possible to hear an echo when he shouted down into the huge pit.
Given the absence of any vegetation and its dark, dull color, the a’a’ lava below where we were standing was clearly younger than on the far side of the caldera where the lava was grayer and supporting a thin veneer of plants. The older material was more than 10,000 years old whereas some of the closer lava had been added during the most recent eruption on the north rim in 2005. Because there had been rain on the volcano the night before, water that had seeped down through the lava was now returning to the caldera surface as mesmerizing tendrils of steam that contrasted sharply with the dull black lava. These steamy wisps gave the volcano an animated appearance that was a clear reminder that it was still active with a magma chamber just 1.3 miles (2 km) below us.
Once we had shouted for an echo and fully absorbed the scale and grandeur of the main caldera, we continued walking NE along the rim towards a recently active volcanic area called Volcan Chico. This area consisted of various parasitic cones and lava flows that had erupted outside the main caldera, from the northern edge of Sierra Negra and Julio explained that our path took us on an accelerated passage through time from formations that were laid down 10,000 years ago to cones that had last erupted in 1979 and sent rivers of lava down to the NW coast of the island.
At the edge of the Volcan Chico area the path, which had been surrounded by well established, shrubby vegetation, abruptly entered an area of exposed lava upon which only the occasional cactus and hardy, creeping plant had been able to establish. The scenery was dramatic, harsh, and fascinating with numerous lava tunnels and intersecting, “frozen” flows of different types and ages of lava. Although the landscape was dominated by grays, reddish-browns, and blacks, at the small scale there was a surprising variety of colors with lava formations in scarlet, orange, yellow, and green. Textures varied from the jagged a’a’ and smooth, shiny ropes of pahoehoe to twisted knobs of colored lava that looked exactly as if various plastic containers had been melted and mixed before suddenly hardening.
We walked about 0.6 mile (1 km) across this Martian landscape to the end of the trail on a cone that had a superb view over the northern end of Isabela and of Isla Fernandina. The trail over the lava was fairly obviously worn but had also been marked with discreet, neatly painted and varnished wooden arrows. There had been no other people ahead of us so our experience seemed particularly remote and other-worldly. It was only as we turned to pose for Julio to take a group photo (he handled our six cameras with great dexterity) did we see that several other tours had followed us and many other visitors were strung-out across the lava field. We were very lucky to be the first people to arrive at the area that day.
We felt well exercised by the time we got back to the campground and we continued to marvel at our good fortune that scattered clouds had developed above and below us but there were still fine views and no rain to make the paths muddy and slippery. It is difficult to describe adequately the fascination of the volcanic landscape and photos rarely do justice to its scale and uniqueness. However, we returned to our boats that afternoon thoroughly satisfied that we had truly experienced some of the raw geological wonders of the Galapagos Islands.