- Landforms from lava
- Landforms from magma
- Hot springs and geysers
- List and describe landforms created by lava.
- Explain how magma creates different landforms.
- Describe the processes that create hot springs and geysers.
geyser: fountain of hot groundwater and steam that erupts under pressure onto the surface
hot spring: place where hot water bubbles or flows continuously out of the ground
intrusion: igneous rock mass that forms when magma cools under the ground
lava dome: dome-shaped landform of igneous rock that forms when thick lava cools near the vent of a volcano
lava plateau: large, flat landform of igneous rock that forms when large amounts of thin lava flow quickly over the ground
Introducing the Lesson
Show students several photos of lava domes, such as those at the URLs below. Ask students how they think these structures form. Accept all reasonable responses at this point, and then tell students they will learn how lava domes and other volcanic landforms are created when they read this lesson.
Discuss the conditions under which lava domes form. Point out that lava domes are formed by viscous (thick) magma that erupts effusively onto the surface and then piles up around the vent. Compare and contrast the lava that forms a dome with the lava flow of a shield volcano. Like a lava flow, the lava that forms a dome generally does not have enough gas or pressure to erupt explosively. Unlike a lava flow, the lava that forms a dome is viscous, so it can’t flow very far, explaining why it piles up around the vent and forms a dome shape.
Help students recognize word parts that can help them figure out the meaning of unfamiliar terms now and in the future. Write the terms intrusive and extrusive on the board. Underline the prefix in- and say that it often means “in,” and underline the prefix ex- and say that it means “out.” Then define intrusive as “projecting inward” and extrusive as “projecting outward.” Explain that intrusive rocks form inside Earth whereas extrusive rocks form outside of Earth, that is, on Earth’s surface. Ask students if they can think of other words that contain the prefixes in- and ex- (e.g., interior/exterior, inhale/exhale, and internal/external). Challenge them to define these words.
If students want to learn about other geysers besides Old Faithful, direct them to the excellent article “The World’s Ten Most Amazing Geysers” at the URL below. The article contains vivid color images and links to videos about ten geysers that are each exceptional for various reasons.
Have students do the inquiry activity “Cake Batter Lava” at the URL below. By doing the activity, students will understand some of the geological processes that occur and structures that form as lava flows across Earth’s surface, using cake batter to simulate lava.
There are many misconceptions about Old Faithful. One of the commonest is that the geyser erupts every hour. Some people even think that it erupts on the hour, say at precisely 1:00 PM, then at 2:00 PM, and so on. Tell students that Old Faithful actually erupts less regularly than that, with intervals between eruptions ranging from about 35 minutes to 2 hours, with an average interval of about 90 minutes. Students may also think that Old Faithful is the biggest or most regular geyser in Yellowstone Park. Inform them that it isn’t the most regular or the biggest, but it is the biggest regular geyser in the park.
Reinforce and Review
Copy and distribute the lesson worksheets in the CK-12 Earth Science for Middle School Workbook. Ask students to complete the worksheets alone or in pairs to reinforce lesson content.
Lesson Review Questions
Have students answer the Review Questions listed at the end of the lesson in the FlexBook® student edition.
Check students’ mastery of the lesson with Lesson 8.4 Quiz in CK-12 Earth Science for Middle School Quizzes and Tests.
Points to Consider
What might Earth look like if there were no tectonic plates? Can you think of any planets or satellites (moons) that may not have tectonic plates? How is their surface different from that of the Earth?
What kind of land formations have you seen that may have been created by volcanic activity? Did these rocks cool above or below the Earth’s surface?
Water is not the only material that can be ejected from geysers and hot springs. What other materials might be ejected from geysers and hot springs?