Hot Topics: Bob Collier and Marvin Lilley -- The Hydrothermal Vent Prospecting Team

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Activity: Current Patterns

Overview
Students can study the air currents within their classroom to examine how wind and ocean currents distribute particles through different environments.

Materials:
Matches or incense.

Procedure:

1. Have the students sit at their desks and close their eyes.
2. Instruct the students to raise their hand when they can smell smoke.
3. Light the match or incense and blow it out.
4. Draw a diagram to "map" the pattern in which students raised their hands. For example, did all of the people in the front smell smoke first, and did any of the students near the window smell the smoke at all? Based on the diagram, have the students (i) try to determine where you were standing when you created the smoke; and (ii) interpret the air currents in their room.
5. What might be the sources of air movement in the classroom? Are there any other factors that might affect how well a student detects the smoke?
6. Repeat the experiment, but change some of the parameters. Have the students raise their hand when they smell smoke, but position yourself in a different part of the room, turn on a fan, open a window, have a couple of students pace back and forth, etc.
7. How do these changes affect the overall patterns?
   

Principle:
Wind and ocean currents move in much the same way, and distribute smells and particles sometimes over long distances. Currents can be fast or slow, and can change daily and seasonally.

Certain winds are always present and drive the world's weather patterns. Winds also drive surface currents in the ocean. The Trade Winds drive surface currents in subtropical regions to the east, while the Westerlies drive surface currents at higher latitudes to the west.

In the deep ocean, currents are driven by density differences, which are caused by variations in the salinity and temperature of deep ocean water. Both surface and bottom currents are also affected by Coriolis force (due to the Earth rotating), tides, the topography of the seafloor, and the distribution of land.

Scientists on board RV Knorr tow CTD sensors that measure conductivity, temperature, and depth) near the bottom of the ocean to help locate hydrothermal vent plumes. Much like students raising their hands when they first smell smoke, the CTD sensors help "sniff" for telltale signs, such as changes in temperature, salinity or water clarity, of hydrothermal vent plumes.