Class lectures part 3 Flashcards
What is subsidence
Sinking of the earth’s lithosphere
What is the Mid Continental rift
Largest failed rift on earth
Failed rifts can happen how? (3 ways)
- Not enough tensional force pulling apart
- Plate reconfigures change forces at edge of plates
- Extension starts occurring in a weaker zone somewhere else
What is Transgression
Shorelines move inland due to sea level rise
What is regression?
Sea level fall, coastal sediments exposed
How does Metamorphism happen?
Due to changes in Temperature, Pressure, Tectonic Stress, Fluids
What is the role of heat in Metamorphism?
Atomic structure changes and heat weakens atomic bonds allowing atoms to rearrange
What are sources of heat energy
- Geothermal gradient
- Magmatic intrusions
- Compression
What are the Metamorphic processes?
- Recrystallization
- Phase Change
- Neo crystallization
- Plastic Deformation
- Pressure solution
What is Recrystallization
Minerals change size and shape but not identity
What’s Phase change
Mineral transforms into a new crystal structure
What is Neo Crystallization?
New minerals form old protolith with different chemical makeup
What’s Plastic deformation
Mineral grains soften and deform
Differential Stress
Stress greater in one direction than another
What is Normal Stress
Stress is perpendicular to the surface
What’s Shear Stress
Stress is parallel to the surface
What is foiliation
Planar fabric that cuts through the rock
Pressure solution
Occurs in ‘Wet’ rocks at low temp
What is Plastic deformation
Occurs at higher temperature
What does Foliated mean
Through going planar fabric (differential Stress)
What does Non Foliated mean
No planar fabric present
What is shearing
Extreme shear causes original contrasting rocks to smear in parallel bonds
What is Metamorphic differntiation
Chemical reactions cause felsic and mafic materials to grow in distinct layers
What is Prograde metamorphism
Occurs when a rock is buried deeply during mountain building
Retrograde metamorphism
Occurs as deep seated rocks are brought back to the surface decreasing temperature and pressure
Metamorphic facies
Set of mineral assemblages that indicate a certain range of pressure and time conditions
Types of metamorphism
Thermal
Burial
Dynamic
Regional
Hydrothermal
Subduction
Shock
What is Contact (or Metamorphic) aureole
Due to heat from a body of magma invading a host rock, alteration bands are created
What is Regional Metamorphism
Tectonic collisions from huge mobile belts
Dynamic Metamorphism
Breakage of rock by shearing at a fault zone
Hydrothermal Metamorphism
Alteration by hot, mineral rich water
Subduction metamorphism
Subduction creates the unique Blueschist (and ecolgite) facies
Shock metamorphism
Impacts generate a compressional shock wave which then generate high pressure minerals
Metamorphic “shields”
Large regions of ancient high grade rocks exposed in continental interiors
Types of lava flows
Basaltic, Andesitic, Rhyolitic
Volcanic deposits may include what?
Pyroclastic debris
Preexisting rock
Landslide debris
Lahars
What are Andesitic or Rhyolitic eruptions
More Si, More viscous, More gas, More explosive, more debris
What is Pumice
Frothy Volcanic glass
What is Ash
Fragments <2 mm in diameter
What is Lapilli
Larger clumps of ash stuck together by water in the air
What are the parts of a volcano
Magma chamber, Fissures, Vents, Conduits, Craters, Calderas
What is a crater
Bowl shaped end of a conduit atop a volcano
Fissures
Linear tear that produces a curtain of fire
Caldera
Gigantic volcanic depression, bigger than a crater
What is Volcanic architecture
Volcanoes come in many shapes and sizes
Categories of Volcanic Architecture
Shield volcanoes-largest
Stratovolcanoes (composite)-Intermediate size
Cinder cones-Smallest
What is a shield volcano
Looks like a shield laying on the ground
What are cinder cones
Smallest volcanos
What are Stratovolcanoes
Large cone shaped volcanoes with steeper slopes
What are Effusive eruptions
Lava outpouring
What are Explosive eruptions
Release pressure catastrophically
What are Strombolian eruptions
Regular “burps” of magma
What are vulcanian eruptions
Moderately sized and explosive
What are plinian eruptions
Huge explosive eruptions
What are Surtseyan eruptions
Vent erupts in shallow seawater
What are convergent boundaries
Most volcanoes form there
What is Flux melting
Subducting oceanic lithosphere adds volatiles
What is an Oceanic Hotspot
Mantle plume under an oceanic plate
What is a continental hot spot
Through a continental plate
What are flood basalts
Voluminous lava eruption above a plume
What is Liquefication
Water saturated soils can lead to liquefication
What is a pyroclastic flow
Superheated ash clouds
What is Ashfall
Buries landscapes killing plants and crops
What can Gas and Aerosols do?
Aerosols can cause respiratory problems in people and volcanic gases can be poisonous
What are Tsunamis
Explosive eruptions at island arcs
What is the Recurrence Interval
Average time between eruptions
How does an Earthquake occur?
Builds up and releases elastic energy along a fault
What is a fault?
A fracture in the crust on which sliding occurs
What is a fault scarp
Displacement at the land surface creates a fault scarp
What is a fault trace
Shows the fault intersecting above the ground
What is a reverse fault
Hanging wall moves up relative to the footwall
What is a Thrust Fault
Special kind of reverse fault
What is a strike slip fault
One block slides literally past the other block
What is displacement
Offset or amount of movement across fault
