How Could the Continents Move? A Lab Activity

Learning Resource Type

Lesson Plan

Subject Area

Science

Grade(s)

6

Overview

Students will begin this inquiry-based activity by predicting how the continents of Earth could move over time. Next, students will complete a lab activity in collaborative groups, in which they will create a model showing how Earth's internal heat energy can create convection currents that result in plate movements. Lastly, students will use their model to explain how Earth's tectonic plates move over millions of years.

This lesson results from a collaboration between the Alabama State Department of Education and ASTA.

Science (2015) Grade(s): 6

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Use models to explain how the flow of Earth’s internal energy drives a cycling of matter between Earth’s surface and deep interior causing plate movements (e.g., mid-ocean ridges, ocean trenches, volcanoes, earthquakes, mountains, rift valleys, volcanic islands).

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Vocabulary

  • Crust
  • Mantle
  • Outer core
  • Inner core
  • Lithosphere
  • Plates
  • Tectonic plates
  • Ocean plate
  • Continental plate
  • Asthenosphere
  • Convection
  • Convection current
  • Magma
  • Divergent plate boundary
  • Theory of Plate Tectonics
  • Convergent plate boundary
  • Transform plate boundary
  • Fault
  • Lava
  • Fissure
  • Geyser
  • Rift
  • Basalt
  • Granite
  • Density
  • Ocean trench
  • Subduction
  • Subduction zone
  • Earthquake
  • Mid-ocean ridge
  • Mountain
  • Rift valley
  • Volcano
  • Volcanic island
  • Undersea canyon

Knowledge

Students know:
  • The layers of the Earth include, from outmost to innermost, the crust, mantle, outer core, and inner core.
  • The crust and upper mantle are broken into moving plates called the lithosphere. These plates are known as tectonic plates and fit around the globe like puzzle pieces.
  • The asthenosphere is located below the lithosphere. The asthenosphere is hotter and more fluid than the lithosphere. Convection occurs in the asthenosphere.
  • Convection is the transfer of heat by the actual movement of the heated material.
  • Through convection, movements deep within the Earth, which carry heat from the hot interior to the cooler surface, cause the plates to move very slowly on the surface.
  • The Theory of Plate Tectonics states that the outer rigid layer of the Earth is divided into a couple of dozen "plates" that move around across the Earth's surface relative to each other.
  • The areas where plates interact are called plate boundaries.
  • The three types of plate tectonic boundaries include divergent (dividing), convergent (colliding), and transform (grinding past each other).
  • Because ocean plates are denser than continental plates, when these two types of plates converge, the ocean plates are subducted beneath the continental plates. Subduction zones and trenches are convergent margins.
  • Subduction zones form when plates crash into each other, spreading ridges form when plates pull away from each other, and large faults form when plates slide past each other.
  • A divergent boundary occurs when two tectonic plates move away from each other. Along these boundaries, lava spews from long fissures and geysers spurt superheated water. Frequent earthquakes strike along the rift. Beneath the rift, magma—molten rock—rises from the mantle. It oozes up into the gap and hardens into solid rock, forming new crust on the torn edges of the plates. Magma from the mantle solidifies into basalt, a dark, dense rock that underlies the ocean floor. Thus at divergent boundaries, oceanic crust, made of basalt, is created.
  • When two plates come together, it is known as a convergent boundary. The impact of the two colliding plates buckles the edge of one or both plates up into a rugged mountain range called a mid-ocean ridge, and sometimes bends the other down into an ocean trench. Trenches are long, narrow, steep-sided depressions in the ocean floor. A chain of volcanoes often forms parallel to the boundary, to the mountain range, and to the trench. Powerful earthquakes shake a wide area on both sides of the boundary. If one of the colliding plates is topped with oceanic crust, it is forced down into the mantle where it begins to melt. Magma rises into and through the other plate, solidifying into new crust. Magma formed from melting plates solidifies into granite, a light colored, low-density rock that makes up the continents. Thus at convergent boundaries, continental crust, made of granite, is created, and oceanic crust is destroyed.
  • Two plates sliding past each other forms a transform plate boundary. Rocks that line the boundary are pulverized as the plates grind along, creating a rift valley or undersea canyon. As the plates alternately jam and jump against each other, earthquakes rattle through a wide boundary zone. In contrast to convergent and divergent boundaries, no magma is formed. Thus, crust is cracked and broken at transform margins, but is not created or destroyed.

Skills

Students are able to:
  • Use a model of the flow of Earth's internal energy and the resulting plate movements and identify the relevant components.
  • Describe the relationships between components of the model including how the flow of Earth's internal energy drives a cycling of matter between Earth's surface and deep interior causing plate movements.
  • Articulate a statement that relates a given phenomenon to a scientific idea, including how the flow of Earth's internal energy drives a cycling of matter between Earth's surface and deep interior causing plate movements.

Understanding

Students understand that:
  • The flow of Earth's internal energy drives a cycling of matter between Earth's surface and deep interior. This cycling of matter causes plate movements.

Scientific and Engineering Practices

Developing and Using Models

Crosscutting Concepts

Energy and Matter

Primary Learning Objectives

Students will create a model of the convection currents that occur within Earth's interior.

Students will use this model to explain how this flow of energy could result in tectonic plate movement.

Procedures/Activities

Before Strategy/Explain: 15 minutes

  1. Show students the following video clip: "100 Greatest Discoveries: Continental Drift" from the Science Channel.
  2. After viewing the video clip, ask students this question: "In the early 1900s, Alfred Wegener believed that the continents had moved, but he was not able to explain why. Now, we have evidence that the continents have moved and are continuing to move today. How do you think this is possible?"
  3. Quick Write: Ask the students to write an answer to this question. Allow student volunteers to share their answers. 
  4. Explain to students they will create a model of the Earth's interior that will show how continents could move over time.

During Strategy/Explore & Explain: 40 minutes

  1. Students will begin the inquiry portion of this lesson (see "Convection Currents in the Mantle Lab Activity" handout for detailed procedures). It is recommended that students be divided into collaborative groups of four to five people for this portion of the lesson.

Lab Activity Summary: Students will begin the lab by setting up the control group. This will entail filling the plastic container with cold tap water and filling the two Styrofoam cups with room temperature water. Students will predict what will happen when five drops of food coloring are added to the water in the plastic container. Students will then add five drops of food coloring to the water and observe the movement of the food coloring for five minutes. Students will record their observations in a pictorial and written format. Students will repeat these procedures two more times: first, filling one of the Styrofoam cups with hot water, then by filling both of the cups with hot water. During the last test, students will add the small pieces of paper or glitter to the surface of the water. Students will observe and record the motion of these objects. 

Note: The lab activity handout instructs students to use the plastic spoon to stir the water between each trial to disperse the food coloring. If the water becomes too saturated to see the movement of the food coloring, students should empty the plastic container and fill it with fresh water.

Safety Considerations: This lab activity requires students to handle hot water. Styrofoam cups are recommended for this activity to insulate the hot water. The teacher should provide safety instructions pertaining to hot water before beginning this inquiry.

After Strategy-Explain & Extend: 20 minutes

  1. Students will use the model they created during the last step of the lab activity to answer reflection questions. These questions will require students to explain how the heat energy present in Earth's interior could create convection currents and cause plate movements.

Assessment Strategies

The teacher will informally assess students as they complete the lab activity to be sure the procedures are followed accurately.

The students will be formally assessed by completing the "Convection Currents in the Mantle Reflection Questions" handout to determine if they can explain how this flow of energy could result in tectonic plate movement. The teacher can count this assessment as a course grade, or use this reflection handout to facilitate a class discussion on the model.

Acceleration

Students who complete the Primary Learning Objective can be challenged to design another experimental group for the lab activity. The students could add additional heat sources, change the placement of the heat sources, or change the temperatures of the water.

Intervention

The teacher should provide assistance to students as they perform the inquiry to ensure the procedures are being followed accurately. The teacher should closely monitor the students during the reflection portion of this lesson and provide support as needed.

Total Duration

61 to 90 Minutes

Background/Preparation

Before beginning this lesson, students should be familiar with the layers of Earth's interior. Although we are unable to study the Earth's interior directly, scientists have studied the interior indirectly using seismic waves. The inner core is a solid sphere of dense metals, while the outer core is liquid metal. The cores are composed of mostly iron and nickel. The convection currents within the outer core create Earth's magnetic field. The layer surrounding the outer core is called the mantle, which consists of extremely hot rock. The upper part of the mantle is called the asthenosphere, this part of the mantle flows very slowly in convection currents. Above the asthenosphere, is the lithosphere, the brittle, rigid part of Earth's crust. The lithosphere is separated into tectonic plates which float slowly on the asthenosphere. 

Students should also be familiar with the concept of convection currents. Convection currents occur when a heat source is applied to a fluid substance. In Earth's interior, energy from the outer core heats the rock of the mantle, causing it to become less dense. This hot rock rises towards the lithosphere, where it cools, becomes denser, and sinks back towards the outer core. Although the convection currents in the mantle are very slow, they cause plate movements over millions of years.

This video clip describes how scientists used indirect methods to discover the interior composition of Earth and describes where Earth's internal energy originates.

"100 Greatest Discoveries: The Core of Earth" from the Science Channel-2:39 Minutes

The assessment portion of this lesson will include questions relating to the control and experimental groups of the lab activity. Students will need to be familiar with the terms control and variables.

Control: This is the trial the scientist performs before testing any variables.

Variables: The factor the scientist changes between tests. 

Materials and Resources

Student Materials (per group)

Safety goggles

Clear plastic container (for example, Sterilite or Tupperware container)

Liquid food coloring

White sheet of paper

Plastic spoon

Two Styrofoam cups 

Small pieces of paper (for example, chads from hole puncher) or glitter

Timer

Student Materials (per student)

Student handouts: Lab Activity Directions and Reflection Questions

Pencil

Notebook paper

Teacher Materials

Water source: This lesson requires cold tap water, room temperature water, and hot water. The hot water can be heated with an electric kettle or hot pot.

Reflection Question Answer Key

Technology Resources Needed

Teacher computer with internet access

Interactive whiteboard and/or projector

"100 Greatest Discoveries: Continental Drift" video clip from the Science Channel (2:12 Minutes)

For background information: "100 Greatest Discoveries: The Core of Earth" video clip from the Science Channel (2:39 Minutes)

Approved Date

2016-08-19
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