Transcript 4_GC1_RockCycle_09

The Diversity and Cycle of Rocks
Rock Cycle
Rock cycle: describes dynamical transformation of rocks
between the 3 rock types
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IGNEOUS, METAMORPHIC, SEDIMENTARY
Where are we going?
• What is the Earth made of? (Of what is the
Earth made?)
• When compounds organize into crystalline
structures….Minerals, otherwise amorphous!
• Minerals combine to form Rocks
Abundance of Elements in the Earth’s Crust
• 98% of the mass of crustal
minerals is from 8 elements
Crystals of a Mineral
Aragonite - CaCO3
Minerals
Mineral: building blocks of rocks
• Naturally occurring
• Homogenous
• Inorganic solid (biominerals okay)
• Fixed crystalline structure
• Definable chemical composition
Quartz (SiO2)
Crystal Structure is
defined by the ordering
of atoms which form a
crystal lattice
This arrangement
produces distinct and
and identifying
properties of the
mineral.
-Cleavage
-Hardness
-Crystal Habit
Cleavage
Mineral Properties
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Crystal Form or Habit
Cleavage
Hardness
Color
Luster
Specific Gravity
Streak
Other Features
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Natural Shape
Broken Shape
Soft or Hard
Clear to Colored
Metallic or NonDensity=mass/volume
Color of powder
Reaction with acid
Crystal Form or Habit
Polymorphs – many shapes
• Same chemical composition
i.e., mineral composed of Carbon
• Different arrangement of atoms in the
crystalline structure
C:
Diamond versus Graphite
CaCO3: Aragonite versus Calcite
Bonding of Atoms into an Ordered Crystalline Structure
Arrangement of Atoms Defines Crystal Properties
Valence of the Silicate Ion or Tetrahedron
The basic building block of all silicates
More Complex Silicate Minerals
Pyroxene
SiO3-2
Amphibole
Si4O11-6
Micas
Seriously Complex
Tectosilicates – Framework Structure
•Quartz
•Feldspars
Common Earth Minerals
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Olivine
Pyroxenes
Amphiboles
Micas
Feldspars
Quartz
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Isolated
Single Chain
Double Chain
Sheets
Framework
Framework
Sequence of Crystallization
Bowen’s Reaction Series
EXTRUSIVE
INTRUSIVE
Igneous Rocks
Igneous rocks: most abundant rock type
• Formed from freezing of magma
at temperatures between about
650-1100 °C
• Intrusive rocks
- Slow cooling within the Earth
• Extrusive (volcanic) rocks
- Erupted on the Surface
Addition of Water Results in Partial Melting
Formation of Felsic and Intermediate Magmas
Igneous Rocks
Igneous rocks: classified by mineral size and composition
• Intrusive rocks
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Crystallized slowly
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Minerals are larger
• Extrusive rocks
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Crystallized rapidly
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Minerals are smaller
IGNEOUS ROCKS – RATE OF COOLING
Intrusive
Granite
Extrusive
Obsidian
Glass
Rhyolite
Rocks Types
Rocks: aggregates of minerals
• Rock types are categorized by their genesis
• Igneous rocks: crystallized from (partly) molten material
• Metamorphic rocks: recrystallized under intense temperature and/or
pressure
• Sedimentary rocks: lithified fragments of pre-existing rock or formed
from biological/chemical precipitation
IGNEOUS ROCKS
METAMORPHIC ROCKS
SEDIMENTARY ROCKS
RELATIVE ABUNDANCE OF ROCK TYPES
SUMMARY