Flashcards in Geo Unit 2 Deck (110):
Igneous rocks make up ___% of the outer 50 Km of Earth
Difference between Lava and Magma
Lava is on the surface of the Earth, Magma is plutonic
What is Magma?
Molten liquid, crystals, and gas
What are the different textures of Igneous Rocks?
Aphanitic, Phaneritic, Porphyritic, and Volcanic Glass
Aphanitic Igneous Rocks
very small mineral grains
Phaneritic Igneous Rocks
Large, visible mineral grains
What is Texture?
The arrangement, size, and shapes of mineral grains
What causes Volcanic glass?
VERY rapid cooling
Large and small mineral crystals/grains
How do you determine the origin of Igneous rocks?
Look at the mineral grain sizes
What is the basis for NAMING Igneous Rocks?
The Silica Content
What are the three composition classifications for Igneous Rocks?
Felsic, Intermediate, and Mafic
Felsic Igneous Rocks?
Light color and Silicon-rich
Mafic Igneous Rocks?
Dark color and Silica-poor
Felsic and Phaneritic?
Felsic and Aphanitic?
Intermediate and Phaneritic?
Intermediate and Aphanitic?
Mafic and Phaneritic?
Mafic and Aphanitic?
What things are part of the creation of magma?
Heat, Pressure, and a small amount of Water
Why is water part of Magma Creation?
A small amount of water allows rocks to melt more easily
What is the melting point of felsic minerals, and when is it reached?
700 degrees Celsius, and reached around the crust/mantle boundary
What is decompression melting?
There is too much pressure for the rocks to be molten, so it must be released before they can melt to become magma
What is Magma Evolution?
The last minerals to melt are the first ones to crystallize upon cooling
What are the last forming minerals in Magma Evolution?
Low temp, stable minerals (vein minerals)
What is Magmatic Differentiation?
The process of forming igneous rocks of different compositions from a single original magma as early-forming minerals remove material from the melt and change it's "recipe" over time
What are the three processes in Magmatic Differentiation?
Crystal Settling, Assimilation of Country Rock, and Magma Mixing
What is Crystal Settling?
Crystals form and sink to the bottom of the Magma Chamber
What is the Assimilation of Country Rock?
Host rock breaks off and falls into rising magma in the chamber
What is Magma Mixing?
Adjacent magma chambers will merge and MIX
How do you get large felsic bodies in the mafic mantle?
Requires PARTIAL MELTING of existing continental crustal rocks to get the silica-rich material concentrated in granites
How are Igneous Rock Bodies formed?
Magma rises and forces its way in through the crust because it is hot, less dense, and is helped by gas expansion
What are the three types of Igneous Rock Bodies?
Dikes, Sills, and Plutons
What are Dikes?
Discordant, Steep and Vertical Igneous Rock Bodies
What are Sills?
Concordant (parallel), Horizontal Igneous Rock Bodies
How do you differentiate a Sill from a Lava Flow?
Look at the grain size, the burn zones, and a Sill will pick up rock from the top and the bottom
What are Plutons?
general intrusive igneous rock bodies
What are Stocks?
Plutons <100 square Km
What are Batholiths?
Plutons >100 square Km
Why is Volcanism common near ancient civilizations?
Volcanism provides many essentials/benefits
What are the benefits that volcanism supplies?
Gasses, water, soils, and geothermal energy along with volcanic soils
How many volcanic eruptions are there around the world every year?
50 to 60
What are the sources of magma for volcanism?
Continental to Oceanic crust collisions
Oceanic to Oceanic collisions
and a little at Continent to Continent
What are the volcanic activity levels?
Active, Dormant, Extinct, and also Mantle Plumes
What defines an ACTIVE volcano?
current or recent activity (historic)
What defines a DORMANT volcano?
Activity within the last 1000 years, and expected to erupt in the future
What defines an EXTINCT volcano?
Not expected to erupt again, sometimes extensive erosion
What is a Mantle Plume?
Stationary hot spot (Hawaii), massive undersea landslides common (TSUNAMI)
What is the most common type of lava?
What are Basaltic Eruptions like?
What are the characteristics of Basaltic Lava?
very fluid flow, travels long distances
How do Basaltic Eruptions erupt?
usually long cracks and flank fissure eruptions, no major cones
Where are there shield volcanoes?
Hawaii and the Snake Plain
What are the two Basaltic Lava Flow types?
aa (ah ah) and pahoehoe (pa hoy hoy)
What are the characteristics of an aa lava flow?
jagged, cindery flows, more viscous
What are the characteristics of a pahoehoe lava flow?
ropey surface (smooth on bare feet) with lava tubes underneath
What makes up a typical Basaltic Flow Architecture from bottom to top?
The Collonade (Columnar Basalt), the Entablature, and the Scoria
What happens when Basaltic lave enters water
What are Andesitic lava flows like?
flow slowly for short distances
Which type of volcanoes are Andesitic?
Stratovolcanoes (Composite Cones)
Are Andesitic eruptions explosive?
What kind of eruptions are common in Andesitic?
What is tephra?
All lava fragments
sand and silt sizes
Bombs and blocks?
What is tuff?
What are pyroclastic flows?
avalanches of hot material
What are Lahars?
What makes up a lahar?
pyroclastic material and water
What is Rhyolitic lava like?
highly viscous, high silicon, low temperature
What can appear before a rhyolitic eruption?
What are the secondary hazards of volcanism?
Temporary global cooling and volcanic gasses
What causes most of the global cooling after a large eruption?
tiny aerosols of SO2
What is the origin of mafic igneous rocks?
divergent oceanic plates, MORBs
Where are andesites and diorites found?
near subduction zones
Why are andesites and diorites found near subduction zones?
The subducted water helps to partially melt the upper mantle
Where are rhyolites and granites found?
on continents near modern/ancient subduction zones
What is weathering?
atmospheric agents cause rocks and minerals to break down
What is erosion?
water, wind, ice, or gravity move materials produced by weathering and deposit them elsewhere
What is Loess?
wind-blown, silty soil
What is the difference between an outcrop and a formation?
an outcrop is an exposed mass of rock and a formation is a distinct mappable unit
What is the difference between mechanical and chemical weathering?
mechanical weathering just breaks it down into smaller pieces, while chemical actually changes the chemical composition of rocks or minerals unstable at earths surface
How do mechanical and chemical weathering work together normally?
mechanical adds to the surface area that chemical can act upon
What are the different mechanical weathering processes?
Frost wedging, Salt crystal growth, Root wedging, Thermal expansion, Mechanical exfoliation, and Abrasion
What is mechanical exfoliation?
pressure unloading on plutonic masses (popping off surface or rock bursts at depth)
What are the different chemical weathering processes?
Dissolution and Carbonic Acid
What is Dissolution?
Water "dissolves" ions from the rock/mineral and carries it away
What stone is particularly vulnerable to carbonic acid?
limestone because of the calcite
What is Hydrolysis?
water breaks down and replaces other ions in mineral structures
What does hydrolysis do to granite?
turns it into grus
What is Oxidation?
mineral ions combine with oxygen ions (rust)
What is Acid Mine Drainage?
Sulfuric acid from mines comes up and joins with surface and groundwater
What is the Regolith?
The "rock blanket" of fragmented material that overlies bedrock
What is soil?
the upper few meters of the regolith that contains both mineral matter and organics
What causes soil horizons?
substances are dissolved and transported to deeper levels by water, forming weathering zones
What are the most common soil horizons?
O, A, E, B, C
What defines the O horizon?
Very organic, carbon rich, plant material
What is the A horizon?
inorganic mineral matter and humus
What is humus?
Carbon rich, dark, derived from organics in O horizon
What is the E horizon?
Zone of eluviation, lighter color, barely any organic matter
What is the B horizon?
Material transported down either mechanically or dissolved, illuviation, concentrated calcite
What is the C horizon?
lowest zone of significant weathering, partially weathered parent material
What are the two old classifications of soil?
Pedalfers (aluminum and iron, organic, fertile) and Pedocals (caliche layer, thin, arid climate)
What are the modern soil classifications?
Vertisols (high clay), Entisols (young soils), Paleosols (ancient, reflect climate changes), and oxisols (tropical)
___% of rocks exposed on land surface are sedimentary
Sedimentary rocks are ___% of crustal volume
What is clastic grain size controlled by?
the original rock type and the transport energy