Class Notes: Volcanism, Plate Tectonics, and Igneous and Sedimentary Rocks Flashcards
What are typical convergent boundary volcanoes?
Typically large composite volcanoes of any composition, mostly Intermediate.
Where are convergent boundary volcanoes found?
On land as arc and chains of volcanoes or as island-arc volcanoes
What causes convergent boundary volcanoes?
Subduction caused - subjecting lab heats due to increasing rural and frictional heat, melting in the 50-200 km depth range
What are typical divergent boundary volcanoes?
mainly fissure eruptions along cracks (faults) caused by plate separation
What causes divergent plate boundary volcanism?
pressure-release melting at ~50 km or less depth
What are hot-spot volcanoes?
mantle plumes not necessarily directly related to main convection cells but superimposed on them.
What are typical hot-spot volcano forms?
typically shield volcanoes of basalt
How do hot-spot volcanoes track plate movement?
Plumes appear fixed and plates move over them, leaving chains of volcanoes tracking plate movement
How do hot-spot volcanoes melt?
Pressure-release melting
Where are common hot-spot volcanoes?
Hawaii
What are two common examples of places with convergent boundary volcanoes?
Cascade Range (land arcs and chains), Aleutian Islands (island-arc volcanoes)
What is an example of divergent boundary volcanism?
Iceland
What are the 6 secondary effects of volcanism?
- acid rain
- particles in atmosphere
- CO2 in atmosphere
- friction between ash and air causes ionization of atmosphere
- landslides
- tsunami (s)
What is acid rain caused by?
volcanic degassing
What do particles in atmosphere cause?
(fine ash and find droplets of sulphuric acid) cause reflection of sunlight back to space causing climatic cooling
What does CO2 in atmosphere cause?
Is a greenhouse gas and helps trap in the atmosphere sunlight reflected off the solid earth causing climatic warming
What two things does friction in atmosphere cause?
- lightening storms
- insect disturbance
What are the two types of landslides? What is the difference?
Rockslides = big chunk of rock--no water Mudflows = clay, sand, silt saturated with water and flows
What are tsunamis?
- seismic sea waves
- large waves caused mainly by displacement of the sea floor 9and locally by landslides into ocean)
What are the two main causes of tsunamis?
1) Caldera formation (formed quickly there is a rapid rush of sea water)
2) Sea-floor fault
How high may tsunamis get up to?
greater than 200 m high
What is the velocity of tsunamis?
800 km/hr
Two types of tsunamis?
1) deep-water waves
2) shallow-water waves
Tsunamis: wave length___, height___, velocity___ as they travel.
- decreases
- increases
- reduces
What are the 4 ways to predict a volcanic eruption?
- mapping and dating volcanic products
- til meters and inflation (if magma coming into volcano is causing it to swell)
- earthquake monitoring (as magma rises it cracks the rock and creates little earthquakes)
- gas monitoring (SO2 increase?)
What are intrusive?
injected as magma into country rock and freezes (crystallizes) in place, at depth, below the earth’s surface.
What are the types of intrusive bodies (8)?
- dikes
- sills
- laccoliths
- plugs (pipes, spines, necks)
- stocks
- batholiths
- magma chamber
- pluton
What is a dike?
- tabular (sheet-like), discordant, commonly nearly vertical
- more common than sill
What causes a dike?
- crack developed and filled with magma
- eroded
What time period are dikes from?
Precambrian
Do all volcanic arcs have dikes?
yes
What is sill?
tabular, concordant, commonly nearly horizontal
What happened to form a sill?
- magma injected into weaker rock
- same composition as dikes
What is a laccolith?
sill with domain top, strata arched over top, discoid
-form from sills where cooling magma is having trouble forming and country rock above gets domed
What is a volcanic plug (spine, pipe, neck)?
feeder pipe coming off dike, sill, magma chamber, lava or volcanic ash form mountain above then and they are eroded.
What is the difference between a stock and a batholith?
their size
If surface area on a map is < 1000 km2 it is a___
If surface area on a map is > 100 km2 it is a ___.
- stock
- batholith