Last week my Geology class talked about volcanoes and igneous rocks. The two seemed to go together as one is made from the other. How can we have a lesson about volcanoes without the vinegar and baking soda volcano activity?
When I did this with my kids at home we made it a multi-day project. We spent one day constructing a clay volcano around a bottle with white air-dry clay. After it dried we painted the whole thing (it was a work of art after all). The next day we "exploded" it. For this class we just constructed a clay volcano (there is a bottle and some newspaper under there), dubbed it "Mount Homeschool" and "exploded" it. A generous portion of baking soda inside the bottle and red-food-coloring-dyed vinegar poured in the top did the trick. If you add some dish soap to the vinegar as well it adds to the bubble effect. Some of the kids lamented the fact that it didn't actually explode, but we talked about how that would be pretty dangerous.
Here are some fun volcano/igneous rock facts:
* Magma - is molten rock below the surface or inside a volcano. Lava is magma that has broken through the crust to the surface.
*Volcanos come in three basic types: Cinder cones are short and steep formed from repeated eruptions of pumice, ash and other debris. Shield volcanoes are wide and somewhat flat and formed by successive flows of runny lava (low silica lava). Mauna Loa on Hawaii is a good example of this. Stratovolcanoes resemble other mountains but are formed from a series of eruptions of different types. These tend to be explosive and have gooey (high silica) lava that doesn't flow as well. Gasses build up over time and then it all comes out in a violent eruption. Mount St. Helens is a great example of this.
*Yellowstone National Park is actually a large caldera, or collapsed volcano crater over a rare- mid-continental hot spot. Magma underneath the ground causes heating of ground water which results in geysers and the like.
* Most volcanoes are formed on the edges of tectonic plates where subduction of one plate under the other causes pockets of lava to rise through cracks or weak spots to the surface. Hawaii is an exception, as it is in the middle of the Pacific plate.
* Fumaroles are holes where steam and other gases come out
* Geysers are where hot water comes out
* A Caldera is a huge volcanic crater formed when a volcano explodes or collapses
* A hot spot is a place where magma rises through the earth's mantle and can break though the earth's crustal plates to the surface.
* A Pyroclastic flow is a hot cloud of ash, gas, and rock that can race down the side of a volcano at up to 200mph. These are much more dangerous than most lava flows, as they move much faster.
* "Igneous" means fiery and igneous rocks are rocks formed from magma or lava. They come in two types. Intrusive igneous rocks are rocks that formed below the surface. Since they are in the earth or volcanoes they tend to cool slowly, giving the rock time to form crystals and larger grains of rock types. Examples include granite, diolite, and gabbro. Extrusive igneous rocks are rocks that formed on the surface from lava that rolled more quickly. These tend to have no or fewer crystals. Examples are pumice, scoria, obsidian, basalt, andesite and rhyolite.
*Minerals are what rocks are made of, they are the ingredients to the rock recipe. The main minerals in igneous rocks tend to be feldspar, quartz, amphiboles and pyroxenes. They also commonly have olivine, mica, magnesium and iron.
I had a limited amount of rock samples to show them. I think the more actual rock types you could get your hands on for this lesson the better. You can order kits of rocks from various learning and scientific sites. My one complaint with the one I got is that all of the samples are just so small. It would have been a lot more interesting if they could handle some big chunks of rock.
Here is a list of resources I used:
Bill Nye: Earth's Crust (video) (This can be found in pieces on YouTube or rented from here.)
Minerals Poster from Feenix Publishing
National Geographic map: Physical Earth (Millennium in maps series)(For an old NG issue, shows volcanoes of the world.)
Books: 101 Questions about Volcanoes by John Calderazzo
How the Earth Works: 100 Ways Parents and Kids Can Share the Secrets of the Earth by John Farndon (Reader's Digest series)
Atlas of Geology and Landforms by Cally Oldershaw
Video of lava entering the ocean in Hawaii
Video of Mount Saint Helens erupting
Rocks for Kids
Geology.com Igneous rocks
Geology for Kids: Igneous rocks
various pictures gleaned from the internet (most rock pictures above are from http://library.thinkquest.org/J002289/igneous.html)