My Observations of Galapagos Land Forms
July 6, 2004
This hot spot is responsible for the formation and eruption the volcanoes that formed the islands. The build up of volcanic material, from the eruptions, over time created the Galápagos Islands. These volcanoes created the unique forms throughout and shapes of the islands. I was fortunate enough to experience and fully learn about the islands first hand through a trip to the Galápagos. Each island I visited looked different than the last. This, I learned, is due to the age of the island and where it is located in respect to the hot spot. The closer the island is to the hot spot, the more volcanoes present, and the number of new land forms is increased and vice versa.
The first island we, the group I was with and I, visited in the Galápagos was Santa Cruz. From the shore line of Santa Cruz, the islands Daphne Major, Daphne Minor and Santiago were all visible. Santa Cruz is a shield volcano that had two distinct times of volcanic activity. The first was the Platform lava series whose result was evident at this location. The results of the second time of volcanic activity are found elsewhere on the island. I saw basalt along the coast, the first verification of past volcanic activity. Secondly, I learned that the sand was composed of marine skeletons. This information is significant in that it suggests that the volcano was involved in a submarine eruption. The materials present on the island verify that volcanic activity was present for the island to form, much of the formation being recent since the platform lava series results range from being 1 million to 2.3 million years old (W.M. White, 1).
The second island that we visited was Bartolomé which is located off the shore of Santiago. The landscape of this island resembled that of Mars. There was very little plant and animal life. The majority of Bartolomé was covered in basalt and volcanic land forms. When water is present in an eruption, like in that of a subduction zone, tuff is created. When there is no water present, basalt is formed. When the volcano that formed Bartolomé erupted, there was not any water present resulting in large amounts of basalt on this island. The basalt hardened together with air creating very light rocks.
One of the first things that I noticed when setting foot on the island was the light dirt substance covering the paths throughout the island. I soon learned that this "dirt" was volcanic ash. However, this ash may not have been from the volcano that formed Bartolomé. It is likely that the trade winds blew the ash from another island's erupting volcano. This particular ash was most likely blown over from Santa Cruz. Though there was not very much plant life on this island, the few plants that were seen were the gray matplant and the lava cactus, both of which generally grow post eruption conditions Still looking just at the ground, there were a lot of areas with pahoehoe lava, mixed in with the mat plant. One of the first land forms that I saw was the lava tube. The plants that grew on this island could be seen paralleling the lava tube. A lava tube is a volcanic structure where, as a lava flow hardens at the surface creating a skin, the liquid lava continues to flow through the middle, hollowing out an area creating a tube like structure.
These tubes could be seen in lines down the mountain. A lava tube forms an outer shell and takes material from far inland, out. It is common for lava tubes to collapse in the center after it has hardened, creating new shapes. The next land form that was frequently seen on this island was that of a spatter cone. A spatter cone forms on land depending on what gases are released at the time of the volcano's eruption. Spatter cones are rocks that have the form resembling that of a sand-drip castle on the beach. These are formed when there is pressure below magma in an active lava flow, and the gases there push upward. The gases escape and carry big pieces of lava into the air where the outside of the lava ball cools down and turns black. Gravity pulls the lava down, and when it hits the ground, the lava ball bursts open, releasing the still hot magma inside. These burst on top of one another creating forms of build up lava "bombs". The outside of these "bombs" are smooth, but the insides when it burst are broken, creating Aa lava. The broken lava, aa, is very runny and breaks and rolls once burst. However, once the gases all escape, then the lava will start to slow, creating pahoehoe. The last land form that I saw on Bartolomé was a crater. When looking off of the top of the island down into the water, a visible outlined circular depression was present.
I think that this form was my favorite to see on the island of Bartolomé. After visiting Bartolomé in the morning, that afternoon we visited the island of Santiago. This part of Santiago was a lava field. This field was created in 1897 or 1898. By looking at the lava, it was possible to tell exactly what the lava was doing at that time during its flow.
Sometimes it changed direction, cracked or even covered something specific and identifiable like a lava tree. A lava tree is a tree that was covered by the lava flow. The imprint of the tree can be seen due to the occurrence of an oxidation reaction in the presence of water. The entire field was covered in pahoehoe lava. Pahoehoe forms when the surface of the lava flow gets hard, but the bottom of it is still hot so the lava keeps flowing making the surface of the flow rope like. The chemical make up of pahoehoe lava includes magnesium, potassium, silicon and iron. The lava has areas where it was metallic and shiny. Some parts of the lava had white lines in it that formed due to evaporation. Other parts of the lava were red; this is due to iron being formed through oxidation. There were pieces of pumice everywhere, mixed in with the basalt. Some sections of the lava had crystallized. This crystallization occurs when lava inflates and breaks coming in contact with the air. It is cooled rapidly and crystallizes. Another form on the island was the driblet cones, which require water to form. The driplets are metallic and shiny. There were few animals and plants on the island. There were lava lizards and painted locus, but no other animals that I saw. The plant present was Mollugo, which grows on lava fields the same way that cacti grow. This lava field appeared to go on for a long time, stretching out into the expanse of the island. I found the visit on to this island to be astounding, different from anything I have ever seen before.
The next morning we visited Elizabeth Bay, which is the body of water between Fernandina and Isabela. This bay is characterized by strong upwellings, and is surrounded by volcanoes. Sierra Negra and Cerro Azul are on one side of it, Volcan Alcedo is on the other side, and Fernandina is opposite the bay. Lava that came from Sierra Negra is found at the opening of Elizabeth Bay.
After visiting Elizabeth Bay, the next area we saw was Urbina bay and then the island of Isabela. Urbina bay is located close to Volcan Alcedo of Isabela. Like on Bartolomé, pumice is abundant, but the pumice had this time come from and eruption from Alcedo. That afternoon we hiked the area surrounding Alcedo. In the distance volcanoes Sierra Negra, Cerro Azul and Volcan Darwin could be seen, Volcan Wolf was hidden behind Darwin. This area around the volcano had vegetation and wildlife present. The walk started on a semi-black beach composed mainly of basalt. I saw aa lava, which was very jagged. At some points during the walk, coral was present on the mainland. This makes me think that at some point the island was underwater allowing for the growth of coral, but after volcanoes erupting, the island was lifted above sea level. This island did not display as many land forms as seen the previous day on Bartolomé or Santiago. The island, though formed the same way, is so different from the others.
The next island we landed on was Fernandina. The excursion began with landing on pahoehoe lava on the coast of the island. However, this lava was inhabited by numerous animal species and not far off of growing plant life. Isabela was visible with the volcanoes Ecuador a glimpse of Wolf to the right of it, and Darwin to the right of Wolf. Further right, behind our landing site, was Volcan Alcedo. Fernandina is a young volcano. A caldera has not formed yet which just further proves its youth. A caldera is when a volcano collapses when magma is released, creating a basin. In the area surrounding Fernandina, pahoehoe and aa could be found right next to each other.
There was one area of the island that had been covered completely with lava that now had water pools throughout it inhabited by many wildlife species. There were not any new land forms that I noticed on Fernandina.
The next day the traveling continued on to the other side of Santiago. We landed on a black sand beach and walked a trail back to and area covered by lava. This area contained numerous collapsed lava tubes on the coast, so that water would flow in and out of the tube making a sound, like toilet flushing, each time a wave hit. These forms were referred to as 'Darwin's Toilet'.
The area was filled with pahoehoe lava and tuffstone. The tuffstoneand lava were mixed together in some areas, shaping the land.
There were numerous cones in this area, but the calderas were not present. Many animals lived on the lava near the water, easily finding places to sleep and hide.
That afternoon, we hiked through Rábida Island. First, we landed on a red sand beach, which was red due to the Iron present in the sand. Hiking through the island, there were not many land forms. At the top of the island, jagged rocks were visible, looking down towards the ocean, but no identifiable structures were present.
The next day we traveled onward to Puerto Ayora, which is a town located on Santa Cruz at Academy Bay. Academy Bay was created due to the formation of a caldera. Later on in the day I entered the highlands, still on the island Santa Cruz. There was only one land form present during this part of the tour. Two craters, "Los Gemelos" had formed in the highlands. The craters were fairly deep and wide around, located not to far off from on another.
Española is the oldest island in the Galápagos Archipelago. Visiting there the next day, this fact became clear. There was more wildlife and plant life located on this island and lesser amounts of new land forms were present, since the volcano there is extinct. There is a cliff overlooking the ocean at the top of Española. Below, on a lava flow, is a blow hole. A blow hole is a hollowed out lava tube where when a wave comes up, water is squirted out of the top of it.
The last island that we visited was Seymour. The unique thing about Seymour is that it displays an ancient sea bed that is located above water. This is due to the island's being uplifted. Besides this fact, and the presence of basalt, there were not any other land forms that I accounted for on Seymour.
My trip to the Galápagos Islands was so incredible, something that is impossible to explain to someone who has not been there. Every view, every piece of scenery is astounding. The scenery and the island in general were both formed by volcanoes originating from a hot spot in the ocean. These volcanoes created forms and shaped each island individually into what they are today. However, the islands are not finished changing. What they are today is not what they will be millions of years from now as they keep moving and continue to be shaped by the occurring volcanic eruptions.