Igneous Rock Formation and Bowen's Reaction Series

Igneous Rock Formation

• Igneous rocks are formed when magma cools and solidifies either above or below Earth's surface.
• Crystallization is the process where atoms or molecules are arranged into a defined repeating pattern known as a crystal lattice.
• Magma that cools slowly beneath Earth's surface forms larger crystals, while magma that cools quickly above Earth's surface has a finer-grained texture.

Bowen's Reaction Series

• Bowen's reaction series is a means of predicting igneous rock formation based on the temperature at which the rocks cool.
• The series shows four groups of igneous rocks: ultramafic, mafic, intermediate, and felsic.
• The mineral composition changes from ultramafic to felsic, with increasing amounts of silica, sodium, aluminum, and potassium.
• The temperature scale shows that minerals that crystallize at higher temperatures, such as olivine, are at the top, and minerals that crystallize at lower temperatures, such as quartz, are at the bottom.

Discontinuous Series

• The discontinuous series contains iron and magnesium-rich minerals.
• The series progresses from high to low temperatures, with olivine minerals rich in iron and magnesium forming first.
• The mnemonic "Olive Pits Are Bitter" helps to remember the order of minerals formed in the discontinuous series.

Continuous Series

• The continuous series involves calcium-rich plagioclase mineral at the highest temperature, which is replaced with sodium as the magma cools.
• The series is continuous, with calcium-rich plagioclase forming at the highest temperature and sodium-rich plagioclase forming at the lowest temperature.
• The mnemonic "C" in calcium coming before "S" in sodium helps to remember the order of formation.

Magmatic Differentiation

• Magmatic differentiation is the process that explains how different igneous rocks can originate from a single magma melt.
• As magma cools, crystals that have solidified within the magma tend to sink due to their increased density, altering the chemical composition of the remaining magma.
• This process results in layers of chemically divergent igneous rocks that settle out of the original magma.
• Magmatic differentiation can result in many different igneous rocks being formed from the same melt.