On day 8, our team was joined by Scott Brame, a professor at Clemson University. With his guidance, we set out to investigate some of the unique volcanic geology of Dominica!
We made our way north along the coast and stopped near Coulibistrie to document evidence of island uplift. Dominica is growing as new volcanic material is added, and marine life preserved above sea level is great evidence of this. The outcrop contains staghorn coral that grew in the ocean and boulders that came from the land. These were mixed together in a shallow offshore setting and subsequently uplifted.
A lookout to the Caribbean through section of uplifted coral.
After Coulibistrie we made another stop along the road and checked out a very colorful wall. This is the Du Blanc outcrop showing a block and ash flow deposit that has been hydrothermally altered.The red and yellow colorations denote different levels of oxidation and reduction of the minerals that were in the hydrothermal fluids.
An outcrop of hydrothermally altered block and ash flow.
After going up and down more winding roads, we found a place to stop and get pictures and video of this beautiful feature. These surge deposits on the road just south of Toucari Bay represent gas and rock fragments ejected during a volcanic eruption with a much higher rate of gas to rock particles. The surge deposits display wavy bedding and are overall well sorted with rounded pumice lapilli. The deposit is underlain and overlain by block and ash flow deposits which indicate it might be associated with a volcanic dome collapse.
Roadcut view of surge deposits south of Toucari.
We ended the day by hiking to one of Dominica’s coolest (in both senses of the word) spots: Cold Soufriere. The springs at Cold Soufriere offgas a significant amount of carbon dioxide and sulfur dioxide, the latter accounting for the pervasive smell of rotten eggs one encounters at the site. The origin of these springs has two possibilities: one, that the hydrologic system is no longer in contact with a magma source or two, that the magma has cooled sufficiently but still contains abundant dissolved gases.
Today was a long day, but it was absolutely worth it to see all these stunning features!
- Stephanie, Emily & Katrina
Clemson Geopaths interns