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80°F (26.7°C)
Latitude: 23 deg 59.3’S
Longitude: 69 deg 38.7’E
Wind Direction: SE
Wind Speed: 12 Knots
Sea State 3
Swell(s) Height: 6-7 Foot
Sea Temperature: 80°F (26.7°C)
Barometric Pressure: 1015.3 MB Visibility: 18+ Nautical Miles

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Daily Update: Finding our first hydrothermal plume
April 3, 2001
By Amy Nevala

It took one touch of the CTD’s icy metal casing this morning to know that it spent a chilly night collecting data and samples in the waters deep below the Knorr.

Yesterday evening when we arrived at 24° South, our first research site, oceanographers Bob Collier and Marvin Lilley lowered the Conductivity, Temperature and Depth (CTD) sensor to begin searching for hydrothermal plumes.

For Collier, it was the beginning of a long night of guiding the CTD up and down in the water column behind the ship as it steamed slowly across the research area.

Sitting at his computer just after 2:00 this morning, Collier noticed a change in the traces of conductivity, temperature and water clarity. A blip in the clarity at a water depth of about 2800 meters (about a mile and a half) told him that there were more particles in that layer of cloudy water.

More particles is one sign of a hydrothermal plume. He immediately collected a water sample for later analysis on board the ship.

By 8:00 am, the CTD had traveled over seven nautical miles of seafloor. Nearly all the water sample bottles were full. Crew members pulled the CTD up and chemical analyses of the water began.

By this afternoon, Collier’s suspicions were confirmed: the water had high levels of the gas methane and the metal manganese in the cloudy layer. These were more signs of a hydrothermal plume.

We have lots of evidence that a hydrothermal vent may be here, but some puzzles remain. Where is the source of the plume? And is there more than one?

Just like smoke from a chimney bends in the breeze, a hydrothermal plume can drift with the currents. This means that the plume may not be directly above the seafloor vent. Now that we have evidence of a plume, our next step will be to locate its source - the seafloor hydrothermal vents.

This will happen when we return here in about a week. Before departing tonight for the next research site at 25°19’S, we deployed a current meter. Scientists use the current meter to measure the speed and direction of ocean currents.

Collected over the next week, data from the current meter will tell us which way the deep ocean currents flow in this area of the Central Indian Ridge. This could help us understand which way hydrothermal plumes drift, thus offering another clue of the vent’s location.

While chemical analyses continue and we review the data we collected today, we will travel to our primary study site at 25°19’S. Tomorrow morning promises to be exciting, as we launch the ROV Jason for its first trip ever to the bottom of the Indian Ocean.

Learn More About...
Hydrothermal Plumes


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