Introduction
Greetings! My name is Peter Belancsik, and I'm currently a junior here at UCD. My major is Environmental Science, and I'm originally from Tallahassee, FL. Since I'm from Florida, I could have picked one of many natural springs, beaches, or swamplands. Instead, I chose the Galapagos Islands, as they've always intrigued me since I was a child first learning about their link to Charles Darwin's studies of evolution. Being an extremist (from a young age), I've always been attracted to the idea of evolution. But the question is, why did Darwin spend so much time in this chain of islands to reinforce his theory of evolution? There are many reasons, most of which will be answered in future blog posts. As far as the habitat goes, most people might conjure up an image of one of the large lizards that call many of these islands home, but I decided to use a picture of a large tortoise that resides in the islands. It was also the closest I could come to getting a picture of a Pinta Island Tortoise, which has now gone extinct (good job, humans). Someday, I wish to visit the islands for their natural beauty and allure. There are over 17 islands that make up the chain, though just to keep it specific, I'll only be talking about 3 or 4. Finally, I picked the Galapagos Islands because like me and my life, they're diverse. After all, what would our world be like without variety?
Diagram showing the east-west ridge spreading center
The Galapagos islands are located off the west coast of South America, with the nearest land mass being Ecuador.The chain of over eighteen islands (otherwise known as an Archipelago), fifteen main and three smaller, lie directly above a tectonic plate called the Nazca plate, which moves east/southeast. The islands were formed by a hotspot (The Galapagos Hotspot), which is a spot in the earth's upper mantle that ascends to melt through the crust to shape a volcanic feature. Most all islands formed by hotspots are, relatively speaking, quite young in the grand scheme of things. On one end of an archipelago lie active volcanoes, with the oldest islands always sitting furthest away from those active volcanoes that helped birth the islands. In this case, the oldest islands have technically been submerged underneath the oceans surface, with the oldest visually noticeable island being Espanola (Hood) island, at around 3.5 million years old. A Mantle Plume is a shot of extraordinarily hot (melted) rock deposited from earths mantle. This is what actually forms the island's solid mass.
Sierra Negra (Shield Volcano), located at the South eastern end of Isabela Island
An early explorer's diagram of Charles (Darwin) Island, showing geological formations, strata, and rock composition of the island
As can be seen in the drawing to the left, the Galapagos islands are basaltic in their composition. Basalt is one of the most commonly occurring extrusive igneous (volcanic) rocks, formed by the flow of lava coming out (extrusive) of the volcano, and cooling in a very rapid manner to create new land. Basalt has a relatively low viscosity, and flows out to form a volcano (usually) with a slope of ten degrees or less, though sometimes a bit more. Geologically speaking, this is called a Shield Volcano, which is roughly circular, or elliptical in shape.
Sources
- http://www.ms-starship.com/sciencenew/galapagos_geology.htm
- http://www.sciencedaily.com/articles/m/mantle_plume.htm
- http://oceanexplorer.noaa.gov/explorations/05galapagos/background/mission_intro/media/GSC3D_600.html
- http://www.youtube.com/watch?v=eKUejHc3Pbw