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Data Collection During Transit

Posted on March 12, 2016
by Maris Wicks

  1b-xbt

The journey from Barbados to the location on the Mid-Atlantic Ridge where popping rocks were once found takes approximately 4 days. During that time, we’ve got data to collect and record! Here’s what we’re looking for and why, as well as the devices that are used to collect that data.

1a-xbt

XBTs (expendable bathythermograph probes) measure temperature as they drop through the water; we deploy an XBT every 8 hours. This gives us information on the change in water temperature to a depth of 1800m, and temperature is important because it affects the sound velocity in the water. Sound is important because we use:

2_multibeam-1000

Multibeam sonar! Multibeam sonar bathymetry is used to map the seafloor. A device mounted on the bottom of the ship sends out a fan of pings (sound pulses) that travel to the sea floor, bounce back to the ship, and are interpreted by a computer to give us an image of the sea floor (a bathymetric map).  The method uses the time that sound returns to the ship to calculate the distance to the ocean floor.

3_gravimeter-1000

The gravimeter measures…gravity! Or rather, the acceleration of gravity. Small fluctuations in gravity can signify changes in the density or thickness of the sea floor beneath the ship.

4_magnetometer-1000

And the magnetometer measures…the magnetic fields! Measurements of the magnetic fields above the sea floor can be used to determine the time elapsed since lava cooled when the sea floor was formed.

In order to monitor the devices and record the data, we’re split into 3 groups that stay on watch (4 hours on duty, 8 hours off duty). Every 15 minutes, we record the data from the multibeam, the gravimeter, and the magnetometer.

Stay tuned for the next post, and learn what these data can tell us about the sea floor!

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About this expedition: Popping rocks revisited

We will be using the research vessel Atlantis, the submersible Alvin, and the autonomous underwater vehicle Sentry, to find and collect samples of “popping rocks”—basaltic seafloor lavas that contain large amounts of carbon dioxide and other gases trapped in high-pressure bubbles that pop when the rocks are brought to the surface. We intend to use these rocks to understanding the composition and origin of gases in the deep earth. This project began with an expedition in 2016 that was cut short due to mechanical problems. You can still see blog posts from the first trip here, and we will continue adding to them during the 2018 expedition.

Recent Posts

  • From Rocks to Rock Stars: A step-by-step guide to how a sample becomes a star
  • A Sacrifice to the Sea
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  • Our Cups Runeth Under
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