Were the Annis Buttes and the Menan Buttes formed at the same time? Are they made of the same kind of lava rock as Craters of the Moon?

Question Answered by Charles Horsburgh retired Geologist

Were the Annis Buttes formed at the same time as the Menan Buttes? They were, and are probably the oldest of what are generally known as the Menan Buttes. The Menan Buttes contains at least six volcanoes, including the Annis Buttes, the North and South Buttes, a non-descript butte between the North and South Buttes that has now been cultivated, and the small Sand Hill Butte that lies to the northwest of the North Butte. The Annis Buttes are probably the oldest because they have been heavily eroded and partially covered by material from the South Butte. They are all around 10,000 years old.

Is the material in the Menan Buttes the same as the material at the Craters of the Moon? The Menan Buttes are unique in that they erupted through the floodplain of the Snake River, that broke the magma into particles known as tuff. Hilton Head on the Island of Oahu is the only other example of a volcanic tuff cone in the world. The Menan Buttes also contain Xenoliths (strange stones) that are pieces of the alluvial material that the magma was erupted through, which are not present at Craters of the Moon. There are several well known ash cones at Craters of the Moon that were formed when molten material (ash) was thrown into the air and fell back to the earth’s surface creating fine grained ash deposits.

North and South Little Buttes (Annis Buttes)
Image: Google Maps

Rock Cycle

The rock cycle is an illustration that is used to explain how the three rock types (sedimentary, metamorphic and igneous) are related to each other and how Earth processes change a rock from one type to another through geologic time. While making the Rock Cycle Starburst model, you will be imitating this natural process.
Materials: aluminum foil, wax paper, Starbursts, toaster oven, towels, oven mitt

  1. wrap 3 Starburst candies. You will be using the same colors in the same order for each rock experiment.
  2. Lay a square of foil flat on the table. Place a square of wax paper on top of the foil.
  3. Stack 3 candies in the center of the papers.
  4. Roll the papers over the Starbursts tightly and form the foil around it.
    Sedimentary Rocks = Pressure Over Time
  5. Apply pressure to the candy packet. You may have to stand on it to apply enough pressure.
  6. Upwrap your Starburst sedimentary rock. Can you see layers? That’s one of the characteristics of a sedimentary rock.
    Metamorphic Rocks = Heat and Pressure
  7. Repeat Steps 1-4.
  8. For this step, you may need an adult helper. Place the Starburst packet into the toaster oven. Cook for 1-2 minutes until the Starburst candy packet is malleable. You don’t want it to melt, just to get soft.
  9. Wrap the foil packet with the towel and apply pressure again. Was it easier to smash the Starburst rocks together?
    10 Unwrap the packet. Did you notice a change to the Starburst colors Did any of the colors mix together? Did you see lines (bands) of minerals. Metamorphic means changed rocks. Did your rocks change?
    Igneous Rocks = Extreme Heat
  10. Repeat Steps 1-4.
  11. Cook the Starburst packet in the toaster oven. This time cook for 5-10 minutes until the candy is melted to a liquid.
  12. Remove from the toaster oven and place it on a towel. Open the packet carefully to prevent burns and watch the candy as it cools.
  13. Once it is fully cooled, pull the candy away from the wax paper and observe. This represents melted rock, which is magma. Can you identify any of the original Starbursts or did they all melt together?
    You have made a trip through the Rock Cycle!

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