Plate Tectonic - Volcanoes (1)
Post Lab 

  • Learning the components of volcanoes.
  • Comparing parts of an erupting volcano.
  • gases
  • hot
  • lava
  • magma
  • molten
  • mountain
  • steaming
  • volcano
  • worksheet
  • pictures of volcanoes
  • Internet

Students draw an erupting volcano.

Cooled lava in Hawaii


Volcanoes form when molten rock, or magma, erupts onto the Earth’s surface. Most magma forms at plate boundaries within the Earth’s crust or upper mantle. The molten rock migrates upward, coming to reside in a "magma chamber" or reservoir below the surface. Magma periodically rises from the magma chamber to the surface, causing eruptions.

Pressure builds up inside the Earth before an eruption takes place. This pressure causes earthquakes, as the rock around the rising magma shifts. Earthquakes in volcanic areas are thus often precursors to eruptions.

Different types of volcanoes have different eruptive styles, depending on the composition of the magma, its temperature, and how fast it moves to the surface. Some volcanoes erupt very violently, spewing pieces of ash, lava, and rock hundreds of meters into the atmosphere. For example, Stromboli is a volcano in Sicily, Italy noted for its violent eruptions. In contrast, Kilauea, a volcano in Hawaii has a quiet eruptive style, lava slowly pours from its vents, flowing downhill.

In addition to lava, mudflows sometimes form during eruptions. Mt. St. Helens, a volcano in Washington that erupted in 1980, is a good example. Mt. St. Helens erupted violently. It literally "blew its top off." However, there was a large amount of snow on top of Mt. St. Helens, when it erupted. The heat of the explosion caused the snow to melt. The resulting water mixed with the ash produced by the eruption, and preexisting loose rock. The resulting mudflows cascaded down the slopes of the volcano at over 120 miles per hour. They caused much damage in the surrounding areas.


  1. Show the students pictures of erupting volcanoes. You may want to use the images or websites mentioned in the Pre Lab.
  2. This exercise gives students skills in drawing an erupting volcano. Before giving them the worksheet, discuss what an erupting volcano looks like. Many times lava will cascade down the volcano and steam will come from the erupting vent. You may also want to discuss the shape the volcano will take after an eruption. It will be similar to the shape before the eruption, but will be larger. (Note: there are exceptions to this rule; some volcanoes are so explosive that the initial eruptions actually blow parts of the volcano away, making it smaller).
  3. Instruct the students to draw an erupting volcano. In the picture, they should draw the hot lava streaming down the sides of the volcano, and the steam coming from its top. Help the students to draw the lava and steam by putting the guide below on the board or projection screen. When they have finished their drawing, have the students write a sentence about their volcano in the space provided.

  1. You may wish to discuss the origin of lava, using the information in the Background. Alternatively, you may want to read a short book on volcanoes to the class, or show them a picture book about volcanoes. If your book describes real volcanoes, make sure you point out on a globe where the volcano is located.
  2. Also explain that when a volcano erupts there are great pressures inside the upper portion of the Earth (crust and upper mantle), and the release of these pressures causes volcanoes and earthquakes. In the next lab the students will start learning about earthquakes.

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