Rocks!

Last week we re-entered, in many ways, Western Civilization. The city of Oaxaca with its paved roads, its tourist hordes, and its urban population was a radical departure from the previous week spent either in Teotitlan or Zimatlan. Coming back produced a feeling of relief for some of us, and a minor culture shock in others.
However, Monday we were offered the opportunity to shift gears once again- moving from the rapid pace of city life to the incredible patience needed to understand geologic time. A new and exciting character, fully academic but quick with a smile and a joke, stepped into our life- Barry Doolan, our fantastic geology professor. Geology class began on Monday with an exercise to understand the global aspect of geology. We split up into teams- The vulcanologists examined a global map of volcanic eruptions, the geomorphologists a map of elevation and landscape, the seismologists a world map depicting recent earthquakes, and the geochronologists a map depicting the ages of the world´s seafloors. Comparing these to a planetary map of tectonic plates, we drew conclusions about the nature of plate boundaries; then worked together to formulate theories that would explain for the different geological activity observed. Understanding the nature of how plate boundaries and faults work gave us a backbone in which to apply our local discoveries and observations.

Thursday, we went to an outcrop on the sides of a busy street in the city. We learned how to measure the strike and dip of points on the outcrop with compasses. We investigated rock particles and crystals with our new hand lenses! Friday, we took the vans out to a quarry where rock is being cut for building stone. We found the fault line and took strikes and dips--while the men working there looked at us with puzzled faces. We stopped for lunch and attempted to find our final destination, yet the road was impassable on four wheels. Instead we hiked around and found a running creek (rare in the dry season!) and identified some billion year old stratified rocks in the water.
Saturday, we had another trip along the road to San Joyctlan. We stopped in five places slowly investigating how the Oaxaca, Todos Santos, Chalcatongo, and Jaltepetonga complexes all meet each other in fault lines along the road. We learned how to compare metamorphic and sedimentary rock, and how to test for limestone (calcium carbonate) using hydrochloric acid.
Along the road we were investigating the rock wall exposed on the side in the blazing southern sun. Three children were curiously watching us after dismounting their horses. After running away and quickly returning they said their mother wanted to invite all of us over for water. That's Mexican hospitality for you. We all followed the children and their mom brought out chairs and water and offered to make comida (lunch) for all of us! We had to kindly decline the offer as we were on a mission, a schedule not always accommodating to "Mexican time". We stayed and talked for a bit to this gracious family as the little children stood in line next to their mother to listen.
At the end of our day after discovering some enormous and interesting fault lines along this long uphill country road, we went out for comida as a group in a pueblo outside of the city and then headed back into town.

Now, with one day off, we will head into week 2 of rocks! Hope all is well in your lives. We send warmth and light your way.

Cheers,
Liz, Keith, and Mollie