Plate Tectonic - Volcanoes (5)

PROBLEM: Do rocks produced by volcanoes provide clues about that volcanic eruption?


Look at a map and locate where the rocks came from in California. Describe the rocks in the area provided below. After learning about the type of eruption that caused the volcano, can you interpret if there is a difference in rock type between a violent eruption and a quiet eruption?

  1. GILROY, CALIFORNIA - This ancient lava flow erupted with a powerful blast. Lava cascaded down the slopes of the growing volcano.
  2. CLEARLAKE, CALIFORNIA - The cinders swished from the volcano, causing extensive deposits, (scoria). Flows of lava cooled quickly to form thick bands of obsidian.
    DESCRIPTION: (scoria)
    DESCRIPTION: (obsidian) 
  3. BLACK BUTTES, CALIFORNIA - Lava slowly moved from the crater of the volcano. A thick layer of basalt was deposited.
  4. MONO CRATERS, CALIFORNIA - the volcano "coughed" violently, gas trapped in the molten rock formed pumice. 
  5. INYO MOUNTAINS, CALIFORNIA - The magma chamber was cooling, but suddenly the volcano erupted formed a rock called andesite porphyry.

CONCLUSION: Are there characteristics of volcanic rocks that indicate what type of eruption produces them?

Is there enough data here to really tell? Explain


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