1.8 - Chile Flashcards
What effect does a high silica concentration in lava have on the properties of the lava and the ensuing eruption?
- Lava has a higher gas content
- Higher pressures within the magma chamber
- Violent eruptions
What are the properties of andesitic lava?
- very viscous
- large silica concentration
- large gas content
What sort of volcanoes are made by andesitic lava?
Composite volcanoes
How do earthquakes occur at destructive plate boundaries?
- oceanic and continental plate move against each other
- tension builds up as plates catch on each other
- pressure is released when plates give way
- EQ occurs
How does the depth of an earthquake affect its magnitude?
- shallower earthquakes have a larger magnitude
- as more energy reaches surface
What are locked faults?
- faults which do not slip due to high friction between both plates at boundary
- accumulate large amounts of stress
- very high magnitude EQs
What is the Benioff zone?
- An area of seismicity
- along the boundary where the subducting plate meets less dense plate
What sort of plate boundary are the Andes on?
- Convergent/destructive
What are the potential secondary effects of an earthquake in the Andes?
- landslides
- avalanches
Which plates interact at the Andes?
Nazca and Antarctic plates subduct under South American plate
What factors cause stresses on a rock face?
- angle of slope
- saturation of the face
- vibrations
- sea, cliff erosion at base
- earthquakes
What factors add to the strength of a rock face?
- consolidation of material
- rock type
- porosity of soil
- tree/vegetation roots
How does the formation of mountains create hazards?
- steepness of mountains can give rise to a large likelihood of landslides
- height of mountains causes moist air from sea to condense, thus rainfall
- folding of rock layers when mountains form creates faults and weaknesses within rock, landslides likely
How does hydrology play into everything?
- rainfall caused by high mountain/volcano peaks pushing moist air higher
- condensation
- snow can accumulate to form glaciers, resulting steep valley sides
- increased stress on mountains