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Tectonics and Volcanoes
Volcanic eruption- Geological disasters
The Rock Cycle
•Inner Core: solid iron:very dense
•Outer Core: Liquid iron: very dense
•Mantle: Iron and Magnesium: Dense
•Crust: silicon and oxygen: low density
•Thin, low-density crust rich in silicon and oxygen
•Composition of the crust
•As a result of planetary differentiation:
•8 elements form 98% of the crust
•Silicon and oxygen account for = 75%
•Flements combine to form minerals
•4000 minerals known, 25 common
•Minerals are the building blocks of rocks
•What is the composition of the crust?
•Minerals and rocks
•Minerals: naturally occurring inorganic solid with ( building blocks or rock)
•Orderly internal structure (atoms are bound together)
•Individual physical characteristics (colour, crystal form)
•Rock: solid aggregate of one or more minerals
•limestone can be made up of one mineral
•others are made up of more minerals Ex. metamorphic
•Biochemistry studies structures of carbon
•geochemistry studies structures of silicon and oxygen
•Basic building block is the silicon-oxygen tetrahedron molecule
•Si-O tetrahedron molecule
•Four oxygen ions surrounding a much smaller silicon ion
•Negative charge, share one or more of the oxygens
•Tetrahedrons combine to form rings, chains, sheets, and 3D structures
•Ex. Single chain share individual oxygens, double chain, sheet,
•Silicates: group of minerals containing silicon and oxygen combined with one or
more other elements
•Most abundant mineral group in the Earth’s crust
•Silicon and oxygen account for = 75% of the Earth’s crust
•What is the rock cycle?
•describes processes by which older rocks are made into new rocks
•Theoretical concept predating plate tectonics
•form by cooling and solidification from a molten liquid called magma
•Crystallization: process of mineral formation in a cooling magma
•Cooling at depth:
•Intrusive igneous rocks
•Most magmas solidify at depth and are later exposed by erosion
•What is Magma?
•Ointment in ancient Greek: partially molten rock below the Earths surface
•Lava: magma that reaches the surface
•as it rises it crystalize because it looses heat
•What are the three components of magma?
•a liquid portion, called melt
•Solid: minerals already crystallized from the melt
•Volatiles: gases dissolved in the melt
•What are the classification of igneous rocks?
•Igneous rocks are classified according to:
•Cooling environment ( crystal size)
•intrusive vs. extrusive rocks
•Mineral composition expressed as % SiO2
•Properties closely related to:
•texture: shape, size, and arrangement of minerals grains
•What is viscosity?
•internal resistance of a liquid to flow
•The less viscous a fluid, the faster it flows
•The most important property controlling magma behavior and, therefore, erup-
•What controls magma viscosity?
1. % SiO2 magma with high % SiO2 has more silicate chains, sheets, and 3D
•More bounds between atoms increase viscosity
2. Temperature Atoms vibrate more vigorously at high temperature
•Bounds between atoms tent to break, decreasing viscosity
3. Amount of solids in the melt ( how many crystals you have in your magma)
•More solids, higher viscosity
•What is low-viscosity magma?
•Tends to reach the Earths surface