Journey to the Center of the Earth:

Interior of the Earth

INTRODUCTION

This activity models the Earth's interior using an apple and a ball of Styrofoam.

Layers of an apple

MATERIALS

WHAT TO DO

  1. Cut apple into 2 pieces (or 4 pieces) from the stem, through the core to the base. Note differences in composition between the skin of the apple, the interior of the apple and the core. Show skin, body, and the core of the apple. Measure the thickness of each unit. Go to Discussion.
  2. Cut the Styrofoam ball into two halves. Cut out the sections of the earth and pin them to the interior flat surface of the Styrofoam ball. Take off one ring of the paper form at a time, and paint or color in with markers that section of the Styrofoam. If using paint, let the paint dry. When paint is dry, put the sphere back together with a marble in the middle to represent the core and cover with blue plastic to represent the crust. Cut continents using template provided for tracing on brown paper (or have them trace continents from globe).  They only need to do ½ earth and another group can do the other half, so that when the spheres are joined, we have a full set of continents. Pin continents on globe. If too difficult . . . place them anywhere, illustrating they do move. They can label the continents with a pen.

QUESTIONS

  1. What do the parts of the Styrofoam model represent in the interior of the Earth? Crust, Mantle, and Core. The combination of the mantle and the crust makes up approximately 85% of the total volume of the earth.
  2. What do the parts of the apple represent in the interior of the Earth? How do the sizes of each unit compare to the sizes for the Earth (ratios)?
  3. How thick should the ocean (the continents?) be in the model? Tissue thin.
  4. Why are there different layers? Discuss. Parts have different properties (and names) because of temperature, pressure, composition, density, and state. With increasing depth, the increased temperature and pressure causes the elements present in the earth’s layers to compact into denser material and causes phase changes. The inner core is composed of solid iron with very low levels of nickel. It has a radius of approximately 750 miles (1220 km) and has a temperature of 8,000 ºF (4,400-7000 ºC). The outer core is approximately 1400 miles (2,240 km) thick and has a temperature of 8000-11,000 ºF (4,400-6,100 ºC) and is liquid iron and nickel. The lower mantle is approximately 1400 miles (2240 km) thick as measured from the end of the core to the beginning of the upper mantle. The temperature of the lower mantle varies from 1600 ºF to 8000 ºF (870-4400 ºC) and the upper mantle is 400 miles (640 km) thick and the crust is 2-75 miles (3-120 km) thick and is solid rock.
  5. Which parts of the model have the densest material? The density increases with depth. The crust has a density of approximately 2.7-3.0 g/cm3; the mantle density varies from 3.7-5.5 g/cm3 with the density increasing with depth; the density of the outer core varies from 10-12 g/cm3; and the density of the inner core varies from 12-13 g/cm3. The average density of the earth is 5.5 g/cm3.
  6. Hottest material? See question number 4.
  7. What is the composition of these materials in the Earth? See question number 4.
  8. How do we know what is inside the earth? Scientists use data from earthquake waves to determine this information. The speed and direction of travel of the waves through the earth provides this information.
  9. How deep has anyone gone inside the earth? How deep have we drilled? Oil companies dig as deep as 8 kilometers in sedimentary rock. Igneous and metamorphic rocks have only been drilled to depths of 2 or 3 kilometers. The deepest well to date has been dug in Russia's Kola Peninsula, which is now approximately 7.5 miles deep. It is important to note that this is still far from getting to the mantle layer.

VOCABULARY

EXTENSION

  1. Label the interior parts with names on paper. Give thicknesses. Label depth range for earthquakes.
  2. Discuss the sources of molten material in mantle. Discuss the inner and outer core.

SOURCES

Presentation, "Eating the Earth" Trisler et al., 2001, SECO Cincinnati.
"Magic School Bus: Inside the Earth." Joanne Cole, Teacher Created Materials, Inc., p.12.
"Physical Geology." Plummer, McGeary and Carlson, McGraw-Hill, 1999.
GEOEDGROUP- The Ohio State University

© S. Olesik, WOW Project, Ohio State University, 2000.

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