Carrie, Ken, Cliff Strain, and I are back in Kaktovik for the summer science program with local students. This week, we have learned quite a lot about local geology by taking sediment cores and exploring local habitats. Kaktovik is located on Barter Island, adjacent to Kaktovik Lagoon, and some of our investigations involve asking how the land around Kaktovik evolved over time: What was here 50,000 years ago? Was Kaktovik Lagoon ever a lake? On our coastal erosion survey*, we found a large deposit of clay sticking out of the base of the cliffs.
Above this clay were layers of sand, pebbles, more sand, more pebbles, and finally dirt and permafrost.
This was a pretty neat find because it indicated that long ago this land was part of a river delta where super-fine sediment grains were able to build up to form this layer of clay. Over time, the environment changed to an area of faster water flow so that coarser sediment grains (sand and pebbles) were being deposited. By looking at this cross section of sediment exposed by the eroding cliff, we could get a picture of how the local landscape changed over geologic time.
*The erosion that had occurred since we did this activity last year was quite apparent. The crevices and caves that we had found last year had all caved in.