igneous rocks and volcanoes
DESCRIPTION
Igneous Rocks and Volcanoes. View From Space - Klyuchevskaya, Russia. Magma – molten rock beneath the surface Lava – molten rock on the surface. Igneous Rocks Cool from the Molten State. Volcanic -- Erupted on Surface Plutonic -- Solidify Within Earth Large Grain Size ---> Slow Cooling - PowerPoint PPT PresentationTRANSCRIPT
Igneous Rocks and Volcanoes
View From Space - Klyuchevskaya, Russia
Magma – molten rock beneath the surface
Lava – molten rock on the surface
Igneous Rocks Cool from the Molten State
• Volcanic -- Erupted on Surface
• Plutonic -- Solidify Within Earth
Large Grain Size ---> Slow Cooling
• Volcanic Rocks -- Fine Grained
• Plutonic Rocks -- Coarse Grained
Porphyritic Texture:Large Crystals in Fine-grained Setting
Igneous Rock ClassificationHow Much Silica? (account for Si)• Excess - Rock Has Quartz • Just Enough to Form Other Silicates • Deficient - Silica-Poor Minerals (Like Olivine)What Feldspars? (Account for Al, Ca, K, Na )• Potash Feldspar KAlSi3O8 • Plagioclase Series
NaAlSi3O8......CaAl2Si2O8
What Other Minerals Are Present? (Account for Fe, Mg)
FeldsparsK - Feldspar: KAlSi3O8
• Several Slightly Different Forms:
• Microcline
• Orthoclase
Plagioclase (Solid Solution)
• Albite: NaAlSi3O8
• Anorthite: CaAl2Si2O8
• Any Mixture of the Two Is Possible
Bowen's Reaction Series
• The geologist N.L. Bowen found that minerals tend to form in specific sequences in igneous rocks
• These sequences could be assembled into a composite sequence.
Bowen's Reaction Series
No igneous rock ever displays the whole sequence, just a slice across the sequence.
Bowen's Series and Igneous Rocks
Bowen's Series and Igneous Rocks
Volcanic Rocks
(Rare) Basalt Andesite Rhyolite
Plutonic Rocks
Dunite Gabbro Diorite Granite
1200 C Melting Point 700 C
Mg, Fe Rich In... Si, Na, K
Rapid Weathering Slow
Usually Dark Color Often Light
Bowen's Series and Volcanoes
Volcanic Rocks(Rare) Basalt Andesite Rhyolite
Plutonic RocksDunite Gabbro Diorite GraniteFluid Lava Is... ViscousMild Eruptions Violent
Type of VolcanoShield Volcano Stratovolcano Plug Dome
Some Igneous Rocks Are Named on Textural Criteria
• Pumice - Porous
• Obsidian - Glass
• Tuff - Cemented Ash
• Breccia - Cemented Fragments
• Porphyry - Fine Matrix, Large Crystals
Types of Volcanoes
A Cinder Cone:
Wizard Island, Crater Lake, Oregon
Anatomy of a Cinder Cone, Hawaii
Tuff Ring: Diamond Head, Hawaii
Tuff Ring: Diamond Head, Hawaii
Shield Volcano: Haleakala, Hawaii
Stratovolcano: Mount Shasta, California
Shastina and Landslide Deposit
Lava Dome, California
Products of Eruptions
Lava Flows
Pyroclastic Debris
• Bombs
• Lapilli
• Ash
Mudflows
Landslides
Gases
• Steam
• Carbon Dioxide
• H2S
• SO2
• HCl
• HF
Environmental Hazards of Volcanoes
Pollution • SO2, HCl in
Water Lava Flows Falling Ejecta Ash Falls • Building Collapse • Crop Destruction
Mudflows • Direct Damage
(Colombia, 1985) • Floods (Several Types)Blast (Mt. St. Helens, 1980) Pyroclastic Flow (St. Pierre,
1902) Gas (Lake Nyos,
Cameroon, 1986)
Pyroclastic Flow or Nuee Ardente (French: Fiery Cloud)
How Calderas Form
Crater Lake, Oregon
Jemez Caldera, New Mexico
Collapsing Volcanoes – Mount Rainier
Collapsing Volcanoes - Hawaii
Evolution of VolcanoesAn active volcanic landscape
Evolution of VolcanoesA volcanic landscape after a million years or so