Magma's composition is ultimately determined by where it forms, including: Those that are relatively higher in magnesium (Mg) and iron (Fe) are called mafic (e.g., gabbro or basalt), while those that are relatively poor in magnesium and iron are called felsic (e.g., granite or rhyolite). Magmas (and the igneous rocks they form) are generally made up of the following eight elements, in order of decreasing abundance: oxygen, silicon, aluminum, iron, calcium, sodium, magnesium, and potassium. Image credit: NASA/JPL-Caltech | + Expand image This graphic shows the interior structure of Earth, the Moon and Mars to scale. This process can produce a wide range of igneous rocks as young material breaches the surface to form new rock structures. The transfer of heat to cooler rocks near the mantle-crust border, combined with changes in pressure, can cause cooler rocks to be assimilated into the magma being forced upward. In the mantle, magma, a heated molten rock, is formed and rises through the process of convection. We can gather these clues, such as a rock’s chemical composition or crystal structure, and use Bowen’s reaction series to also understand the conditions under which they formed.īy now, students have learned that our Earth is composed of a solid inner core, a liquid outer core, a mostly solid mantle, and a rigid crust that floats on the mantle and moves around over geological time due to the activity of tectonic plates. Igneous rocks, which form from magma, have diverse characteristics that provide geologists with clues about the environment in which these rocks formed. Remind students of the expectation that their materials are not to be consumed unless it is safe to do so at the end of the activity.Consider having students construct their silicates on a sheet of paper or a paper towel instead of on their desks and tables.(Optional) representative mineral samples Management (Optional) multicolor marshmallows to use as additional elements Regular marshmallows (about 10 per group of three to four students) In this activity, students will use marshmallows to model the formation of silicates – the family of minerals that make up more than 90% of Earth’s crust – then analyze their chemical and physical structures.
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