Why do winds blow from the ocean to the land or from the land to the ocean?

In the Film

The relationship of cold water and hot, dry land creates many wonders. Winds are a natural outcome of differential heating between hot desert and cold water. Winds cause the movement of the surface water that allows cool water to well up from the ocean depths. This cool, nutrient-rich water is the basis of the marine food web.

Concept

Winds are the result of differential heating.

Objectives

To demonstrate the relative heating and cooling of dirt and water

Content

Science, language arts

Background

When exposed to the heat of the sun, soil warms more quickly than water. As the land warms, so does the air directly above it. As this warm air rises, cooler air from over the ocean flows toward the land. This onshore wind may provide a cooling effect for what would otherwise be an extremely hot region. As the sun goes down, the land cools more rapidly than the water. In early evening the air over the ocean is warmer than the air over the land, and the flow of air is reversed producing an offshore wind.

Per group: two 8 oz. plastic cups, dirt, water, 2 thermometers, 2 goosenecked lamps with 60-watt bulbs, pencil, paper, crayons

(teams, small groups)

• Review or discuss the circulation patterns of warm and cold air.
• Fill one cup with water, the other cup with dirt.
• Hold a thermometer just below the surface of each. Observe and record the readings. Remove the thermometers.
• Place a lamp over each cup, about two inches above the surface. Turn the lamps on. Wait five minutes. Again, take and record the temperature of the water and the dirt.
• Continue recording at five-minute intervals for 15 minutes.
• Turn off the lights. Continue observing and recording the temperatures at 5-minute intervals for another 15 minutes.
• Arrange your data in chart or graph form, plotting temperature and time.
• Compare the respective heating and cooling of the dirt and the water.
• Draw a picture showing land with ocean water next to it. Use your observations from above and draw arrows to show the direction of an offshore wind. Repeat, showing an onshore wind pattern.

Local Connection
Investigate wind patterns in your local area; air circulation in your classroom.

Key Words
onshore, offshore

Continue to Activity 6: Upwelling