Lesson 5: Turnover and Upwelling

Getting Started

Reminder: Before you begin this lesson, go back and do the 1-day mass measurement for the "Water and Estuaries (Saltwater Activity)" experiment that you started in Lesson 3.

In this lesson, you will begin to investigate a cause and effect relationship that is important to the hydrosphere and the ecosystems it contains. While water is the primary component of the hydrosphere, the reservoirs that make up the water planet have sediment and nutrients throughout them. The presence of these nutrients was briefly introduced in Lesson 4; in this lesson, you will look at the ways that these nutrients collect and where they are located in various reservoirs.

You will be looking at these important ideas: sedimentation, turnover, and upwelling. Sedimentation occurs when particles that are floating in water (or another solution) settle out of the water and come to rest against a barrier like the bottom of a body of water. Turnover is the mixing of lake water of varying densities that causes nutrients to mix throughout the water, and upwelling is the process by which cooler, denser waters rise to the surface of coastal areas. As you are investigating these concepts, think about density, which you studied in Lesson 1. Keep in mind what you have learned about density and consider how important density is to the movement of nutrients and sediment in a body of water. Today's activities will deal with the concepts of turnover and upwelling.

Stuff You Need

  • Protecting Earth's Water Supply by Ron Fridell
  • 3 soil samples from the local area
  • desk lamp
  • one-quart clear jar with lid
  • small fan
  • thermometers (kit)

Ideas to Think About

  • Why is density so important for lakes and oceans?
  • What would happen if upwelling and turnover did not occur?
  • How are turnover and upwelling different? What makes both important for life in the hydrosphere?

Things to Know

  • Sedimentation is the settling of particles that were floating in a solution.
  • Turnover is the mixing of lake water of varying densities that causes nutrients to mix throughout the water.
  • Upwelling is the process by which cooler, denser waters rise to the surface of coastal areas.
  • Eutrophication is a process where water bodies receive excess nutrients that stimulate excessive plant growth.
  • Hypoxia is a lack of oxygen.


  • Analyze evidence to explain observations, make inferences and predictions, and develop the relationship between evidence and explanation. (S)
  • Analyze and evaluate information from a scientifically literate viewpoint by reading, hearing, and/or viewing scientific texts, articles, and events in the popular press. (S)
  • Analyze the unique properties of water, including density. (S)
  • Evaluate evidence (such as marine ecosystems, upwelling, and turnover) that Earth's oceans are a reservoir of nutrients, minerals, dissolved gases, and life forms. (S)

Introducing the Lesson

Before your child begins today's lesson, ask him to go back and do the 1-day mass measurement in the "Water and Estuaries (Saltwater Activity)" experiment.

As your child progresses through this unit, he should be developing the ability to make connections about information. For Lesson 5, the goal is for your child to develop an understanding and appreciation for processes that aren't normally observed and to learn how to evaluate what is observed. Your child will observe a process known as hydrologic sorting (the sorting of materials in water) and use this observation to increase his understanding of the importance of density. Then your child will choose one of two options to investigate an important process that occurs in aquatic environments: either turnover or upwelling. Both processes are distinctly different, yet the result of each is the same — the delivery of nutrients to two of the larger reservoirs found in the hydrosphere: lakes and oceans.

In this lesson, your child will be challenged to go a step further and make inferences, which are generalizations based on observations. The goal is a challenging one because students sometimes have a tendency to care only about the "right answer." What is sometimes overlooked but is of equal importance is that your child begin to understand the process of questioning through observation and concluding through analysis of these observations. A good scientist will challenge and continue to challenge until understanding is complete and there is an assurance that conclusions are correct based on observations of data. That "one answer" is to interpret the information gathered and use it to develop more questions. You and your child are strongly encouraged to go back and do activities again. The quest for answers is as much the goal as are the answers that have been found.
Reading and Questions
Materials: Protecting Earth's Water Supply by Ron Fridell
Read pages 12-13, 25-26 and pages 40-41 in Protecting Earth's Water Supply. As you are reading, focus on developing an understanding of the terms eutrophication and upwelling. Continue seeking to make a connection between your developing understanding of the hydrosphere and its components and how these components are important for life on the water planet.
  1. How do sediments and erosion damage rivers and oceans?
    Soil that is not held in place by plant roots erode quickly during rains to turn into sediment that clogs rivers and estuaries.
  2. Describe the process of eutrophication.
    Nitrogen and phosphorus enter the water as pollution. They cause algae to grow, and when the algae dies, it sinks and decomposes. Decomposition uses up oxygen. Fish begin to die from lack of oxygen in the water, or hypoxia, and when their bodies also begin to decompose, this uses up even more oxygen.
  3. Based on your reading for this lesson, what is a large area with eutrophication and hypoxia called? Why do you think its called this?
    Its called a dead zone, and it is called that because many ocean animals die when eutrophication and hypoxia happen, and nothing new can live there.
  4. Can dead zones be reversed? What can be done to reverse a dead zone? How do you know this can work?
    Yes, dead zones can be reversed by cutting back on fertilizer that pollutes ocean water with phosphorus and nitrogen. We know this because the Black Sea had areas of eutrophication in the 1980s because of farm fertilizer runoff. When the Soviet Union split up in 1991, fewer farmers could afford fertilizer, and life returned to that part of the Black Sea.