Ees 1030 1st Edition Lecture 3 Current LectureIgneous Rocks: formed by the cooling and solidification of magma. (Volcanic rock)- Magma is formed by the melting of rocks in the hot deep mantle and core. - When magma is at the surface it is called Lava Crystallization of magma/Lava:- Water changes from liquid to solid at 0 degrees C - Magma changed from liquid to solid at 200-300 degrees - When magma cools different minerals crystallize and grow. Intrusive:- Rocks that are formed from magma deep intro earth’s surface are called intrusiverocks. They form by slowly cooling magma. Also can be called Plutonic.Extrusive:- Rocks formed from lava cooling at earth’s surface are called extrusive rocks. Formed by lava cooling quickly. Also can be called Volcanic.Nature of Magma:- Liquid portion- melted rock- Solid portion- silicate minerals - Gas or volatiles- water vapor, carbon dioxide, and sulfur dioxide. Classifying igneous rocks:- Based on: texture, types of minerals, and chemical composition.Igneous Textures:Aphanitic: fine grained rock, crystals are too small to see with the naked eye. Cools very quickly. Basalt is a good example. Can contain holes from gas being released.These notes represent a detailed interpretation of the professor’s lecture. It is best used as a supplement to your own notes, not as a substitute.Phaneritic: course grained with crystals larger than 1 mm. magma cools slowly so crystals have time to grow freely. Porphyritic: large crystals are imbedded in a matrix of fine grained crystals. Minerals are formed at different temperatures. Pegmatic: extremely course grained rock with very large crystals formed in magma that is rich in fluids. Glassy: fast cooling, with high silica content. Pyroclastic: produced by volcanic eruptions, appears similar to sedimentary rocks, Volcanic breccia has particles larger than ash. Vesicular: forms with bubbles in the magma as gases exsolve. Rapid cooling causes bubbles. Pumice: used for dead skin removal, in heavy duty soap, and for stone washed jeans. Use as a cement additive. Common Minerals:- Si, O, Fe, Mg, Ca, Al, Na, K.- Igneous rocks are primarily composed of silicate minerals. Mg, Fe- ferromagnesian are dark silicates.- Ca, Na, K- nonferromagnesian are light silicatesColor:Felsic: lighter colored minerals like Feldspar, quartz, and SilicaIntermediate: slightly darker in color, not black or light. Contains feldspar or biotite. Mafic: dark minerals that contain green minerals like olivine. Chemical composition of magma:Composition siO2 Tem ViscosityBasaltic 50% 1200 C Low viscosityAndesitic 60% 1000 C IntermediateRhyolitic 70% 800 C High viscosity- The more viscous a volcano the more explosive. Volcanos with higher viscosity have runnier magma that erupts more explosively. - A volcano with low viscosity will have more sticky magma and will erupt less explosively Origin of magma:Basalt: high temperatures with low silica and low viscosity. Also low gas levels. Eruptions are flowing. Forms shield volcanos, scoria cones and craters.Andesite: medium temperatures with moderate silica and gas content. Moderate viscosity. Flowing and moderately explosive eruptions. Thick rubbly lava flows. Pumice and ash fall after eruptions. Cinder-cone volcano. Rhyolite: low temperature. High silica and gas content. Also high viscosity. Very explosiveeruptions with pumice and ash falling, lava will flow if magma has low gas levels. CalderaVolcanos. How molten rock is made: (Origin of magma)1. Increase in temperature. (thermal)2. Decrease in density (decomposition)3. Add gases and violates (fluid-induced)Adding violates causes rocks to melt at lower than normal temperatures. Magma Variations: One volcano can erupt lavas with different