Density of the Earth\'s Crust PDF

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Summary

Density of Earths Crust lab assignment. GEOL 4406...

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Module 3 Activity: Density of the Earth’s Crust Purpose:

To determine the density of rocks that make up oceanic and continental crust.

Materials:

AWS-600 Digital Scale (measuring in grams) Rock samples representative of Earth’s crust labeled Module 3 Earth’s Structure Plastic beaker from lab kit (do not throw away) Water Paper towels Food coloring (optional) Pencil Calculator Printed copy of this worksheet, Density of the Earth’s Crust

Procedure:       

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Source:

Number or organize your rock samples 1-8. You may use a sharpie to label them if you like. Use the scale to find the mass of each rock in grams. Record the mass of each sample on the Rock Density Table. Pour 50 ml of water into the plastic beaker. You may want to add a little bit of food coloring so you can see the water levels more clearly or use a sharpie to make the lines on the beaker easier to read. Carefully place your first rock sample in the beaker. Be sure there is enough water in your beaker to completely cover your sample. If there is not enough water to cover your sample, remove the rock and add 10 ml of water (you will now have 60 ml of water in your beaker) and replace the rock. Make a note of the new water level, then subtract your beginning water level from this amount (if your beaker now reads 63 ml, then 63 – 50 = 13 ml). Record the difference as your volume (1 ml = 1 cm3; 13 ml = 13 cm3). Calculate the density of this sample (d = mass / volume) in g/ cm3 Repeat for each rock sample. Using the calculated density of each rock, determine the type of crust where each of these rocks might be found. Place your rock samples on a paper towel to dry completely before returning them to their appropriate bag in your laboratory kit. See the Post Module Activity webpage for instructions about returning the rocks to their appropriate bag for future activities.

Modified from The Earth Through Time Laboratory Manual by Faulkner, SFA Department of Geology

Module 3 Activity: Density of the Earth’s Crust

Rock Density Table

Volume Density (cm3) (g/cm3)

Type of Crust

Sample Number

Mass (g)

1

54.4g

20ml

2.72

Continental

2

20.2g

10ml

2.02

Continental

3

28g

10ml

2.8

Continental

4

18.3g

8ml

1.83

Continental

5

25.7g

9ml

2.85

Continental

6

29.5g

10ml

2.95

Oceanic

7

18.7g

5ml

3.74

Oceanic

8

23g

10ml

2.3

Continental

Discussion Questions 1. What is the average density for the continental crustal rocks you measured?

2.42g/cm^3 2. How many samples represent continental crust?

6 3. What is the average density for the oceanic crustal rocks you measured?

3.34 4. How many samples represent oceanic crust?

2

Module 3 Activity: Density of the Earth’s Crust 5. What observations can you make about the rocks that represent continental crust versus those that represent oceanic crust? It is interesting to me that out of the 2 rocks that represent the oceanic crust, one of them is one of the heaviest rocks and the other one is one of the lightest rocks. The physical characteristics of these two rock are triangular in shape, two of the smoothest rocks, and one of them is a pinkish color and the other one is a dark grey color.

6. Devise a hypothesis that explains why the position of the oceanic crust is lower than continental crust. Clearly state your hypothesis here:

Due to the process of subduction, the oceanic crust is colder in temperture and becomes denser with age. It gets so dense that it sinks below the continental crust.

7. The Earth’s core is composed mostly of iron with an average density of 10-13 gm/cm3. If the core were made of less dense materials, how would this affect the mass of our planet?

Because the earths core makes up most of the earths mass, if the materials at the core were lower density, then the earth would decrease in mass.

After you have completed the Density of the Earth’s Crust activity and answered the questions, upload your completed worksheet to the Module 3 Activities dropbox on d2l. Allow your rocks to dry then follow the instructions on the Post Module Activity webpage to return your rocks to their appropriate bag....