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Draft 1: Galapagos Triple Junction Article

Introduction

The Galapagos Triple Junction (GTJ) is located off the western coast of South America and has been studied for its Geologic structure of an abnormal triple junction. Although this collision is not uniform in its entirety, Geologists and Scientists have used various form of study to try to understand it’s history. Overtime, it has been hypothesized that the Triple Junction of the Nazca, Cocos, and Pacific Plate was once colliding through different directions and velocities of plate movement, which has over time adjusted providing new tectonic formations like spreading ridges and the Galapagos Micro-Plate (Smith, D. K., et al.). Collision of oceanic plates often cause specific landforms like volcanic arc systems, whereas divergent plates cause trenches and seafloor. Both structures are seen in the GTJ area, implying that not only convergent boundaries are present but divergent as well. Determining relative ages of the geology in the area is challenging due to consistent volcanic activity along spreading ridges and trenches bordering each plate boundary.

Location (Google Earth)

• 1.4°S, 99.8°W
• The collision zone is just East (about 600 miles form the famous Galapagos Island, which is approximately 1300 miles West off the coast of Ecuador.

• 

  This image shows the location of each plate relative to one another, while also displaying the location of the Galapagos Micro Plate created form the Cocos, Nazca, and Pacific Plate Triple Junction

  
  

Geology

Triple Junctions occur when three plates typically meet in the shape of a ‘T’ with one plate along the top line of the ‘T’, and one on both sides of the vertical perpendicular stem of the ‘T’. All three of these plates are colliding at its intersection point of both the vertical and horizontal lines. (Cox, A. & Hart). Like plates all over the world, each plate moves with its own unique direction and speed. Each plate is moving with a different velocity which can change the outcome and shape of the whole Triple Junction (Cox, A. & Hart).

In the Galapagos Triple Junction, the three corresponding plates don't collide perfectly but instead display differences in responses to collision. For example, in a perfect scenario the Nazca Plate, Cocos Plate, and Pacific Plate would all meet at a complete 'T' shape (Smith, D. K. et al.). The GTJ doesn’t form a typical Ridge-Ridge-Ridge Triple Junction. In plate collision, this would be the ‘perfect’ scenario. Divergent and convergent plate boundaries can form ridges, trenches, and/or faults. The shortened ‘R’ ‘T’ and ‘F’ are used to symbolize when put together what kind of structures are formed on the plate boundaries. In collisional plate movement such as these, geologist use these letter symbols to determine the kind of junction created from colliding plates, so the perfect scenario would be ‘RRR’, one for each edge of the colliding t-shape.

Since this collision is not uniform or consistent, the Galapagos Microplate is being created via different velocities and directions that have changed over millions of years. In the GTJ, the Pacific Plate, Cocos Plate, Galapagos Microplate and Nazca Plate are all the present tectonics at work (Smith, Deborah K. et al.). This activity is causing 3 different rift areas, an extended volcanic ridge, and a large dominant spreading center (Smith, Deborah K. et al.). The Pacific plate is moving the fastest at 95 mm/yr NE, then the Cocos Plate moving relatively N-NW 67 mm/yr, and 40 mm/yr E –NE for the Nazca Plate (Smith, D. K. et al.). Differing border velocities that detect the rate of spreading as well as the lack of/slowing of spreading are also considered as well (Smith, D. K. et al.).

To detect these plate boundaries, landforms were identified using bathymetry and sample drilling. Drilling obtained data of rock compositions that make up this area along seafloor spreading ridges. Peridotite, gabbro, basalt and diabase are present (Smith, Deborah K. et al.) which are all deep ocean rock forms that similarly make up ophiolites. This is understandable since the spreading ridge is made up of rising magma from the mantle.