Background Info

¡Hola todos from Costa Rica!

So now that we’re here on the ship (Melville) maybe we should tell you what we are doing with your hard-earned tax dollars. Tomorrow we’ll head off to the Galapagos for a month of sea-floor mapping and rock sample collection. The main Galapagos archipelago is formed from the same type of mantle plume that created Hawaii and other island chains. However the region is especially interesting and complicated because of its proximity to the Galapagos Spreading Center – a mid-ocean ridge where new ocean crust is created.

Mantle plumes and mid-ocean ridges traditionally have different geochemical and morphological characteristics. Mid-ocean ridges tend to be depleted in certain elements that were incorporated into the formation of continental crust. However, mantle plumes have retained these elements. This difference gives the two magma sources different geochemical signatures.

Both mantle plume and mid-ocean ridge activity seem to occur in our study region, north of the Galapagos archipelago. The primary objective of our cruise is to determine how these two sources interact by mapping the area and analyzing rock samples taken from the ocean floor. Several models have already been proposed to explain the interaction between these sources. The end-member models argue that volcanism between the spreading center and the hot spot is either caused by excess magmatism generated by the proximity of the hotspot or faulting caused by tensional stresses near the mid-ocean ridge. The presence of a transform fault (a fault roughly perpendicular to the spreading center that off-sets the ridge) creates additional stress on the crust that could potentially cause it to fracture, allowing magma to seep through the cracks.

In order to paint a complete picture of the area, we will employ an interdisciplinary approach, collecting both geochemical and geophysical data. Specifically, we will be towing an underwater camera and using sonar imaging to generate images of the sea floor. Specifically, we will be using a tow cam designed by Dan Fornari of Wood's Hole Oceanographic Institute (WHOI). The tow cam will be towed behind the ship and will take pictures of the ocean floor at a pre-determined interval, allowing us to have high-resolution, true-color imagery. We will also be measuring changes in gravity, which could track differences in crustal thickness and reveal areas of buoyant mantle. Finally, we will use our seafloor images to locate sites to dredge for rocks. These rock samples will be analyzed in lab after the cruise for distinctive geochemical signatures.

By looking at the data we collect, we hope to be able to prove or disprove these models and gain insight into one of Mother Nature’s most perplexing geological quandaries.

¡Hasta luego!

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