Name ______Date ______Class ______

Igneous Rock Lab

Problem:How can you tell the difference between intrusive and extrusive igneous rocks?

Hypothesis: ______

Materials:Diorite, olivine, granite, rhyolite, basalt, obsidian, magnifying glasses

Instructions:

1.Divide the rocks into two categories: intrusive (large crystals, coarse grained) and extrusive (no

crystals, fine grained).

2. Place the rocks in the proper row from lightest to darkest.

3. After you have placed the rocks in their proper places,

  • Name the rocks and label.
  • Outline/label the blocks with felsic rocks with a red marker.
  • Outline/label the blocks with mafic rocks with a blue marker.
  • Outline/label the blocks with intermediate rocks with a yellow marker.

Data Table/Observations:

Intrusive rocks
(coarse grained)
Extrusive rocks
(Fine grained)
Color / Lightest / Middle / Darkest
» » » » » » » » » Silica content decreases » » » » » » » » »
» » » » » » » » » Rock color becomes darker » » » » » » » » » »

Don’t forget to answer the questions on back.

Conclusions:

  1. Was your hypothesis right or wrong? Explain your answer.
  1. How can you tell the difference between extrusive and intrusive rocks?
  1. How are igneous rocks formed?
  1. Where do extrusive igneous rocks form?

5. Where do intrusive igneous rocks form?

6. What substance causes igneous rocks to get darker?

7. If an igneous rock contains large substances of silica, it is classified as a (felsic, mafic) rock.

8.How does the cooling rate of lava affect the texture (crystal size)of igneous rock?

9. How does the cooling rate of magma affect the texture (crystal size) of igneous rock?

10. What is the difference between magma and lava?

ANSWER KEY

Igneous Rock Lab

Problem: How can you tell the difference between intrusive and extrusive igneous rocks?

Hypothesis: ______

Materials:Diorite, olivine, granite, rhyolite, basalt, obsidian, magnifying glasses

Instructions:

1.Divide the rocks into two categories: intrusive (large crystals, coarse grained) and

extrusive(no crystals, fine grained).

2. Place the rocks in the proper row from lightest to darkest.

3. After you have placed the rocks in their proper places,

  • Name the rocks and label.
  • Outline/label the blocks with felsic rocks with a red marker.
  • Outline/label the blocks with mafic rocks with a blue marker.
  • Outline/label the blocks with intermediate rocks with a yellow marker.

Data Table/Observations:

Intrusive rocks
(coarse grained) / Granite / Olivine / Diorite
Extrusive rocks
(Fine grained) / Rhyolite / Basalt / Obsidian
Color / Lightest / Middle / Darkest
» » » » » » » » » Silica content decreases » » » » » » » » »
» » » » » » » » » Rock color becomes darker » » » » » » » » » »

Don’t forget to answer the questions on back.

Conclusions:

  1. Was your hypothesis right or wrong? Explain your answer.

Answers will vary.

  1. How can you tell the difference between extrusive and intrusive rocks?

Intrusive rocks are coarse grained with large crystals.

Extrusive rocks are fine-grained with small or no crystals.

  1. How are igneous rocks formed?
    Molten material (melted rock) cools and solidifies.
  2. Where do extrusive igneous rocks form?

On the earth’s surface; exited the earth.

5. Where do intrusive igneous rocks form?

Inside the earth.

6. What substance causes igneous rocks to get darker?

Less silica

7. If an igneous rock contains large substances of silica, it is classified as a (felsic, mafic) rock.

8. How does the cooling rate of lava affect the texture (crystal size) of igneous rock?

Lava is extrusive so it cools quickly; crystals do not have time to form.

9. How does the cooling rate of magma affect the texture (crystal size) of igneous rock?

Magma in intrusive so it cools slowly; crystals are large.

10. What is the difference between magma and lava?
Location – Lava is “outside” and magma is “inside” the earth.