Semester 2 Flashcards
What is a volcano?
Surficial manifestation of a planet or moon’s internal thermal processes through emission of solid, liquid or gaseous products at discrete surface locations
What was The Volcanic Age of Observation?
- William Hamilton
- 1750-1900
- James Hutten, the father of geology
- Neptunists vs Plutonists
What were Neptunists?
- believe earth was static
- every rock was the result of precipitation from recreation ocean
What were plutonists?
- earth in a constant state of flux (dynamic earth)
How did volcano knowledge change in 1900s?
- pre 1970s volcanology more descriptive (not interpreted)
- Modern been more explanatory and investigative (volcano monitoring, hazard analysis, remote sensors)
What is MAGATH? (factors control style of volcanic activity)
- Material (molten rock or ice)
- Available volatiles (gases)
- Gravity
- Atmospheric pressure
- Tectonic environment
- Heat generation mechanism
What are the 2 main ways heat is generated?
- Radiation (decay of radioactive isotopes in interior liberates heat)
- Tidal forces (astronomical objects deform the interior, liberating heat)
How is heat loss in a volcano?
Convection through plate tectonic snd mantle plumes
- conduction
- convection, mantle plumes
- convection, plate tectonics
2 main types of volcanos
- Stratovolcano’s
- Shield volcanos
What are stratovolcanoes?
built from layers of viscous lava flows and pyroclastic rocks from explosions
What are shield volcanos?
layers of fluid lava flows, convex profile and can be enormous
2 types of magma
- low viscosity magma
- high viscosity magma
What is low viscosity magma
- magmas such as basalt
- produced at mid-ocean edges and hot spots
- create shield volcanos
What is high viscosity magma?
- Andesite and rhyolite give rise to silicic volcanism
- produced at subduction zone settings
- create stratovolcanoes
What is eruptive style determined by?
- Magma type
- Viscosity (more silica more viscosity)
- amount go gas present (gas causes explosivity)
What are the levels of silica compared to viscosity?
low (50%) - Basalt
medium (50-65%) - Andesite
high (>65%) - Rhyolite
What is magma a complex mixture of?
- Melt (molten rock)
- Crystals (solid rock)
- Gas
What is andesitic and rhyolitic volcanism?
- gas can’t move freely
- pressure builds up leading to pyroclastic explosions
- eruptions lead to pyroclastic density currents (PDCs), causes column collapse
What are 3 features of andesitic and rhyolitic volcanism?
Craters
Domes
Calderas
What are components of the cryosphere?
seasonal snow
glaciers
ice sheets
sea ice
ground ice
river/lake ice
2 facts about ice
lighter than water, 900kg m3
reflective (high albedo)
What happens when snow survives summer melting?
Undergo transformation into ice
Characteristics of glaciers?
ice thickness - 10 to 100s m
length - 1 to 10s km
velocity - 1 to 100m/yr
Characteristics of glaciers?
ice thickness - 10 to 100s m
length - 1 to 10s km
velocity - 1 to 100m/yr
2 ways of accumulation for glacier
Snowfall
Avalanches
How does metamorphism of ice work?
Accompanied by densification (pores close of at 800)
- new snow (50-70)
- settled snow
- firn
- glacier ice (830-917)
Ways of ablation
wind removal
melting + run-off
(iceberg calving)
What is the equilibrium line altitude (ELA)?
located where annual mass balance is zero
