quiz question do you expect that the earthquake in hawaii was: –tensionsal (pull-apart movement)...
TRANSCRIPT
Quiz Question
• Do you expect that the earthquake in Hawaii was:– Tensionsal (pull-apart movement)– Compressional (push-together movement)– Shear (moving-past movement)
• Given the geologic setting of Hawaii, why do you expect this?
What defines a specific mineral?
Crystal structure and Chemical Composition
Mineral Name
Quartz
Corundum
Diamond
Graphite
Chemical Composition
SiO2
Al2O3
C
C
Crystal structure
Framework Silicate
3-D framework
Sheets
The Silicate MineralsBasic Building Block
Silicate ion: SiO4-4
One Si surrounded by 4 O in a tetrahedron. Can be combined in different ways:
•Isolated tetrahedra
•Chains
•Sheets
•3-D Framework
Rocks, some context
• What is a rock?– A coherent, natural, aggregate of minerals (or
glass)
• Types of rocks– Igneous - formed from melt– Sedimentary - formed by surface processes– Metamorphic - formed by transforming other
rocks
Let there be… magma
• Where is magma formed? In the lithosphere– At subduction zones (addition of water)– At midocean ridges (decompression)– At rifts (decompression)– At hot spots (decompression)– In next to other magma (contact)
PlateBoundaries
What is a Metamorphic Rock
• Metamorphic rocks are formed by metamorphism of other rocks– Changes in physical, chemical, and
mineralogical characteristics– In Solid State
Metamorphism
• What causes rocks to metamorphose?– Heat (different mineral stability, faster reactions)
– Hot water (addition/removal of elements)
– Confining Pressure (different mineral stability)
– Directional forces due to deformation
Weathering
• The conversion of solid rock to smaller pieces or other (non-rock-forming) minerals
• Physical v. Chemical weathering (they work together!)
Physical weathering
• … the process whereby large rocks are broken into smaller rocks.
• Many different processes
Chemical Weathering
• Dissolution = dissolving salt in water
• Hydrolysis
2 KAlSi3O8 + 2 H2CO3 + H2O
Al2Si2O5(OH)4 + 4SiO2 + 2K+ + 2HCO3-
• Oxidation (where does the Fe+2 come from?)
4 Fe+2 + 3 O2 2 (Fe+3)2O3
• The role of organisms
Transport (erosion)
• What transports sediments?– Water, primarily– Wind
• Why?– Ultimately, for water: gravity
Sedimentary Rocks
• Sediments: layers of loose particles that originate from the weathering of the continents (solid debris or dissolved substances)
• Sedimentary Rocks: Rocks formed from sediments by the process of lithification.
• Two types
– Clastic Sediments
– Chemical and Biochemical Sediments• Requirements
– Weathering– Erosion– Deposition– Lithification
Principal of Original Horizontalityand the
The Law of Superposition
Sediments (and sedimentary rocks) record conditions on the (local) earth’s surface at the time they were formed.