Download The Rock Cycle

The rock cycle
The Rock Cycle
Reading: Pages 51-78
Review Questions
Ch 3: 1-5, 17, 18
Rock cycle
Lava
™Shows the interrelationships among the
three rock types
™Igneous
™Sedimentary
™Metamorphic
sediment
Sedimentary rock
1
Metamorphic rock
Convergent lava generation
Plutonic rock genesis
Rock cycle
Full cycle does not always take place due to
"shortcuts" or interruptions
• Igneous rock is metamorphosed
• Sedimentary rock is weathered
• Metamorphic rock weathers
Igneous rocks
Magma cools and crystallizes
• Inside Earth -- plutonic or intrusive rocks
• On the surface --volcanic or extrusive rocks
Formed from lava (a material similar to magma, but
without gas
2
Scaling El Capitan
El Capitan
Igneous textures
Crystallization of magma
Ions become crystals
Crystal size is determined by the rate of
cooling
• Slow = large crystals
• Fast = microscopic crystals
• Very fast= no crystals-- forms glass
Coarse-grained igneous
texture
Coarse grained
3
Fine-grained igneous texture
Fine grained andesite
Porphyritic igneous texture
porphyritic
Glassy texture
Pumice
4
Vesicular
Texture
Size and arrangement of crystals
• Fine-grained – fast rate of cooling
• Coarse-grained – slow rate of cooling
• Porphyritic (two crystal sizes) – two
rates of cooling
• Glassy – very fast rate of cooling
Classifying Igneous Rocks
• Texture
• Mineral content
Felsic rocks
Composed almost entirely of light-colored
silicates - quartz and feldspar
• Felsic: feldspar and silica (quartz)
• High silica content (about 70 percent)
• Common rock is granite
granite
rhyolite
5
Mafic rocks
basalt
Contain substantial dark silicate minerals
and calcium-rich plagioclase feldspar
• Mafic: magnesium and ferrum (iron)
• Common rock is basalt
gabbro
Intermediate rocks
• Mixture of magmas
• Less common than basalt or granite
• Andesite and Diorite
andesite
diorite
6
Classification of igneous rocks
based on texture and mineral
constituents
Igneous rock classification chart
with photos of rocks
Mineral composition
Bowen’s reaction series
• Explained by Bowen's reaction series
which shows the order of mineral
crystallization
• Influenced by crystal settling in the magma
Magma body before settling
Crystal settling
7
More crystal settling
Most common igneous rocks
• Granite
• Basalt
Mineral resources
• Reserves are already identified deposits
• Ores are useful metallic minerals that can be
mined at a profit
• Economic factors may change and influence a
resource
Hydrothermal (hot-water)
fluids from magma bodies
Metallic mineral resources
• Gold, silver, copper, mercury, lead, etc.
• Concentrations of desirable materials are
produced by
• Igneous processes
• Metamorphic processes
• Sedimentary processes
The Bingham copper
mine in Utah
Metallic mineral resources
•
•
•
•
Hot water
Contain metal-rich fluids
Associated with cooling magma bodies
Types of deposits include
• Vein deposits in fractures or bedding
planes, and
• Disseminated deposits which are
distributed throughout the rock
8
Nonmetallic mineral
resources
An underground halite (salt)
mine
• Make use of the material’s
• Nonmetallic elements
• Physical or chemical properties
• Two broad groups
• Building materials (e.g., limestone,
gypsum)
• Industrial minerals (e.g., fluorite,
corundum, sylvite)
9