7 weeks 5 days
Submitted by Dena Rosenberger on Sat, 11/17/2012 - 20:23
Where are we now?
Site: U1412B or CRIS-9B, off the western coast of Costa Rica, in the Pacific Ocean. Our coordinates are N 8°30 min, W 84°8 min. Nice cumulus clouds all around. Air temperature is 28 °C (82 °F) and the water temperature is still 33 °C (91 °F)
We are currently drilling at about 160 meters below sea floor (mbsf) and it will take a few more hours to do a mud sweep, cut the first XCB core, and put down the wireline to retrieve the core barrel. We are expecting more core between 8:00 and 9:00 tonight! Our target depth is 500 mbsf at this hole. Keep your fingers crossed!
MAD scientist! Physical Properties Specialist Liz Screaton is busy measuring samples taken from the cores. MAD stands for Moisture And Density.
She dries each core sample in a 105 C oven for 24 hours and uses the before and after masses to determine the moisture content of the sample. Then, to calculate the density, she puts each sample into a small container with a known volume and fills it with helium gas. The gas fills in all of the spaces in the rock (called “pore” space), and with this information and knowing the volume of the container, she can calculate the volume of just the rock. So with the mass and the volume, she can now calculate density.
These two pieces of information can tell the scientists how compact, or “consolidated,” the sediments are, which may be an indicator of how resistent this particular rock might be to certain types of waves during an earthquake. The less consolidated, the more shaking damage might occur. Mexico City is on unconsolidated landfill. Couple this with poor construction of many of the homes and buildings and you have a recipe for disaster when earthquakes have occurred.
Life on Board
Today marks the halfway point in the expedition! To celebrate “Hump Day” we are having a BBQ at 5:00 pm for dinner on the deck, and a beach-themed party in the Movie Room at 9:00.
Oh, and don’t forget we are expecting cores about 9 pm!
As usual, the kitchen staff put out a wonderful array of salads, BBQ choices, and scrumptious desserts. What a feast!
To see more pictures, visit our Facebook page!
From the subduction zone, off the coast of Central America…