Magma Viscosity, Volatile Content, Partial Melting, & Mixing- Igneous Petrology #6 | GEO GIRL

What controls how explosive a volcanic eruption is? This video covers the difference between felsic and mafic magmas in terms of their silicate content and structure and the crystallization processes and rocks that result from each, how volatiles like water and CO2 affect magma viscosity, and how the viscosity of magma affects the explosivity of volcanic eruptions, the factors that control magma viscosity and density, how density affects magma ascent and eruptions, how melts are formed, in particular how partial melting works, how fractional crystallization works, and lastly, what magma assimilation and magmatic mixing means. Viscosity of magma determines how explosive its eruption at Earth's surface will be. Volatiles content and temperature of magma controls the viscosity of the magma. Explosive eruptions occur when volatiles in viscous magma exsolve as the magma rises to Earth's surface and the pressure changes. This extreme change in pressure when the magma reaches the surface leads to a huge push to get the magma to explode out of a volcano, where it then becomes lava then solidfies into igneous rock. Felsic magmas are typically more viscous than mafic ones, thus mafic eruptions are more like oozing flood than explosions, which leads to flood basalt formation. For the second half of this video, I go through magma differentiation by partial melting and magma mixing which can occur in magma chambers below Earth's surface. Partial melting lead to eurpted lavas that are always more felsic than their source because felsic material melts at lower temperatures than mafic material. This melting/crystalization trend follows the Bowen's Reaction Series, which I talk more about here: Igneous Rocks and Bowen's Reaction Se.... Hope you enjoy this video and learn as much as I did in making it! ;D

References: Essentials of Igneous Petrology by Ronald and Carol Frost: https://amzn.to/37Zs9AL
Earth Materials by Cornelis Klein and Anthony Philpotts: https://amzn.to/3z5sCxe

GEO GIRL Website: https://www.geogirlscience.com/ (visit my website to see all my courses, shop merch, learn more about me, and donate to support the channel if you'd like!)

0:00 Felsic vs mafic magmas
3:43 How volatiles affect volcanic explosivity
7:21 How volatiles affect viscosity and vice versa
9:04 what happens when you blow bubbles in viscous materials?
10:10 What controls viscosity?
11:18 How magma density affects eruptions
13:34 Partial melting of magmas
18:59 Fractional crystallization of magmas
21:40 Magma assimilation & mixing
23:13 Upcoming videos!

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