Lithosphere: the Solid Earth What’s below the surface: Rocks
But what’s inside a rock?
Yes, but What’s a Mineral? 1 cm Rock- a natural aggregate of minerals (and/or mineraloids)
- a naturally occurring, inorganic, crystalline solid with a definite chemical composition and characteristic physical properties e.g., quartz, diamond, graphite, talc Mineral
= study of the composition, properties, & classification of minerals (Geo 321- offered in Fall)
Minerals id’d by
What is a crystalline solid? Are any inorganic solids not crystalline? Glass
How do we know a material is crystalline? Self-Similarity Halite Quartz
How do we know a material is crystalline? X-ray diffraction
Chemistry of the Solid Earth The Big 8 Elements
The Earth’s Crust O 46% -2 Si 28% +4 Al 8% +3 Fe 5% +2/+3 Ca 4% +2 Mg 3% +2 Na 3% +1 K 2% +1 Element Abundance Charge 99%
SiO 2 - Quartz
Silica Tetrahedron SiO 4 What is the charge? Si = +4, O = -2 thus -4 How can that be?
(Fe, Mg) 2 SiO 4 - Olivine
How old are the oldest rocks on Earth?
Given: Sample from Acasta Gneiss in Canada
It has crystals of zircon that
contain 238 U.
238 U is unstable.
It decays into 206 Pb.
ZrSiO 4 ~Fixed chemical formula. But a few U’s can be used To substitute for Zr.
How do Minerals Form? - Cooling from liquid (magma) to a solid
How do Minerals Form? - Evaporation of a briny liquid - Cooling from liquid (magma) to a solid
How do Minerals Form? - Precipitation from a fluid Section of a pipe Mineralized vein - Evaporation of a briny liquid - Cooling from liquid (magma) to a solid
Asbestos- fibrous silicate mineral w/ fireproofing qualities Ceiling tiles
Asbestos- commercial term, not a geological term Chrysotile- sheet structure no sharp fibres- no hazard Crocidolite- chain structure sharp fibres- BIG hazard The Cost- 50 to 150 billion $ to clean it all up >half of the asbestos is harmless Chrysotile What to Do?
What is a rock again?
= assemblage of minerals (or mineraloids) in a solid state
Igneous Sedimentary Metamorphic Plutonic Volcanic
1. Igneous rocks ( fire-formed )
= rock that solidified from a molten state
majority of crustal rock (although it is often covered with sedimentary rocks)
consists of silicate minerals w/ metallic elements