Geology Vocab!

Being out on the JOIDES Resolution is a learning experience for me! I teach high school marine science and Advanced Placement Environmental Science, so being here, in the world of geochemistry, geophysics, and volcanology (just to name a few disciplines) is taking me out of my zone of familiarity.

One job for the scientists on board is to describe the cores- this sounds like a pretty straightforward task, right? Not so much! Some parts of core description include:

  • Macroscopic visual description of split cores
  • Microscopic observations from thin sections
  • Description and measurement of structures
  • Data collection & analysis of digital images, diffuse color reflectance, and magnetic susceptibility

All of the above means there’s lots of discussion and collaboration by the scientists- they all have their own individual tasks, but then have to assemble all the data into a coherent unit. Reading up on their reports has shown me that there’s a whole world of terms that I am unfamiliar with. It seems as though I’m learning new definitions every day! A few examples include:

  1. Vug: a small cavity in a vein or in rock, usually lined with crystals of a different mineral composition from the enclosing rock.
  2. Breccia: a course-grained clastic rock, composed of angular broken rock fragments held together by a mineral cement or fine-grained matrix.  Basically, it translates to “broken stones”. 
  3. Clastic: pertaining to a rock or sediment composed principally of fragments derived from pre-existing rocks or minerals and transported some distance from their places of origin.
  4.  Fluid Inclusion: a tiny cavity in a mineral, 1.0-100.0 microns in diameter, containing liquid and/or gas, formed by the entrapment in crystal irregularities of fluid, commonly that from which the rock crystallized.
  5. Thin Section: a fragment of rock or mineral mechanically ground to a thickness of approximately 0.03mm, and mounted between glasses as a microscope slide. This reduction makes renders most rocks & minerals transparent or translucent, thus making it possible to study their optical properties.

**All of the above definitions attributed to: Bates, Robert L., and Julia A. Jackson. Dictionary of Geological Terms, Doubleday, 1984.

So, for someone who doesn’t have much of a background in the subject, I really am enjoying learning as the expedition progresses. Hopefully I’ll be able to take my newly expanded vocabulary back to my classes and teach MY students about it!







Hello there! My name is Tammy Orilio and I am sailing on board the JOIDES Resolution, Expedition 376: Brothers Arc Flux as an Education & Outreach Officer. I look forward to sharing both science and shipboard life with you! In my other life, I teach Marine Science and Advanced Placement Environmental Science at Marjory Stoneman Douglas High School in Parkland, FL. I love being able to share these experiences with my school community!
More articles by: Tammy

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