Feeling a Thermocline
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Rationale/Objectives/Purpose:
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This activity offers students a tactile experience of a thermocline.
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Time Required:
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Teacher preparation: 1 hour
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Student Activity: 30 minutes
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Safety Issues:
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Use caution when heating or obtaining warm water.
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Materials:
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Large pot or bucket for each student group.
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A second smaller container for each group.
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Ice or chilled water.
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Warm water (If hot water tap not available, consider using an old drip
coffemaker, be sure to test water first to avoid scalding.)
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Procedures:
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Teacher:
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Assign students into groups of 2 to 7 per group.
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Pass out printed instructions and review with students.
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Monitor student movement and assist.
Student:
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Fill your large container 1/3 full of warm water
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Fill your second container with cold water
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Carefully pour the cold water into the warm water.
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After 20 seconds slowly dip your hand into the water, all the way to
the bottom of the container.
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Observe as you dip your hand the depth where the cold water begins.
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Assessment:
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Have students write observations and possible explanations.
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Teacher Background/Extensions:
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Incorporate more measuring activities (volume of water, temperature,
depth of thermocline. Use different colors of food coloring to do a visual
demonstration using appropriate see-through container.
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Background: The "thermocline" is the region where water temperature
changes rapidly over over a relatively short chang in depth. Colder water
is denser and therefore stays below the less dense warm water. The different
densities create a seperation between the warm and cold water at a particular
depth. During an El Niño event, in the eastern equatorial Pacific
the thermocline is significantly deeper, causing less nutrients to come
up to the surface. With fewer available nutrients, the phytoplankton (tiny
light-harvesting plants in the sea that make up the base of the marine
food web) do not bloom (grow in high numbers). This affects every
level up the food chain.
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