Name: _________________________________ Date:_______________ Period:____
Saul 2012
EARTH SCIENCE Density: Continental High, Ocean Low Basalt and Granite
Focus Question: Which has a greater density: Basalt or Granite?
Background:
Ocean crust is made mostly of iron-rich igneous rock known as basalt. Continental crust is mostly
composed of silica-rich igneous rock called granite.
Purpose:
In this activity we will test the density of the rock that makes up the ocean crust and the continental crust.
Procedure:
1. Use the triple beam balance to find the mass of each rock then record in Table 1 or 2.
2. Practice the Water Displacement Method to obtain the volume of the rock by pouring water from
the beaker into the graduated cylinder to the ______ mL line.
3. Gently tip the graduated cylinder slightly and slide the rock into the graduated cylinder
4. Record the volume of the rock + water in the data table
5. Calculate the volume of the rock only by subtracting the start volume from the volume of the
water & the rock.
6. Pour the water back into the beaker and remove the rock.
7. Find the rock’s density by dividing the Mass of Rock by the Volume of Rock.
Rock Name
Mass (g)
Average Density of OCEAN Crust
Volume of
Volume of
Start Volume
Water & Rock
rock ONLY
(ml)
(ml)
(ml)
Density of
Rock
g/cm3
Average
Density
g/cm3
Average Density of Continental Crust
Volume of
Volume of
Start Volume
Water & Rock
rock ONLY
(ml)
(ml)
(ml)
Density of
Rock
g/cm3
Average
Density
g/cm3
Basalt 1
Basalt 2
Basalt 3
Basalt 4
Basalt 5
Basalt 6
Rock Name
Granite 1
Granite 2
Granite 3
Granite 4
Granite 5
Granite 6
Mass (g)
Data Analysis QUESTIONS
1. What is the experimental average density of basalt, which makes up the ocean crust?
______________
2. What is the experimental average density of granite, which makes up the continental crust?
______________
3. By carrying out experiments similar to the one you just performed, scientists have determined the
average density of basalt (ocean crust) to be 3.0 g/cm3 and the average density of granite (continental
crust) to be about 2.7 g/cm3. Compare your experimental average densities to the true density values of
granite and basalt and discuss at least 2 possible sources of error that could account for inaccuracies in
the data?
4. Use the outcome of this investigation and specific data to explain why the ocean crust sits below sea
level even though it is much thinner than the thick continental crust, which rests above sea level.
5. Make a prediction: How might the density values for the mantle and the core compare and contrast to
the oceanic and continental crust?.