Flashcards in Vulcanicity- Content Deck (59)
What is an example of flooding resulting from lava flows?
Spirit Lake rose 80m after the eruption of Mount St Helen's
What are the benefits of volcanoes?
- hot rocks allow the development of geothermal power
- lava flows create new land
- igneous rocks make good building materials
- lava and ashes= fertile soils
- tourist attractions e.g. geysers and hot springs
- extinct = defensive sites
- volcanic sulphur= pharmaceutical manufacturing processes
- valuable mineral deposits
Example of geothermal power
Example of extinct volcano as a defensive site
Example of valuable mineral deposits
Gold silver and diamonds in Java
What is the type of magma at constructive?
Above 1000 degrees C
What is the type of magma at destructive?
Up to 1000 degrees C
What are the characteristics of magma at constructive?
- low in silica
- thin and runny (less viscous)
- gas can escape
What are the characteristics of lava at destructive
- high in silica
- viscous and thick
- traps gas
What is the type of eruption at constructive?
Low on VEI scale e.g. Hawaiian
not very explosive as gases are able to escape, lava
What is the type of eruption at destructive?
High on VEI e.g. Vulcanian, Plinian
can be extremely explosive with ash, dust and lava
What is the eruption height at constructive?
2km and less
What is the eruption height at destructive?
55km and below, can be way over 20km
What are the materials produced at constructive?
What are the materials erupted at destructive?
- pyroclastic material
- ash and dust
- lava bombs
What is the frequency at constructive
Eruptions are regular but can be continuous
What is the frequency at destructive?
less frequent, often have long dormant periods
What is the form of volcano at constructive?
- basic shield volcano or lava plateau
- made of only lava
What is the form of volcano at destructive?
- composite cone or acid lava dome
- layers of ash and lava
- very viscous lava
What are the hazards of volcanoes?
- ash falls ruin crops/machinery, disrupts transport, breathing
- lava flows burn and bury crops
- dust emissions create rainstorms; dangerous lahars
- dust absorbs solar energy and lowers atmospheric temps
- pyroclastic flows; life and property
- flooding results from lava flows/debris blocking rivers
- submarine eruptions= tsunamis
What are the two types of volcanic landforms?
1. Extrusive igneous rock formation (volcano)
2. Intrusive igneous rock formation (not a volcano)
What happens to intrusive rock forms?
- lava cools quickly when in contact with air
- this creates crystals so rock is finer grained
- e.g. basalt
What are the solid material coming from volcanoes?
- glassy cinders
What are the gases released by volcanoes?
- carbon monoxide
- hydrogen sulphide
- sulphur dioxide
What are the liquids released by a volcano?
- surface lavas e.g. acid, basic
- lava bombs e.g. tephra or pyroclasts; solidify in mid air e.g. Forming pumice, fine hairlike trails of magma called lapili
What are the three types of lava?
1. Basic lava
2. Andesitic (intermediate) lava
3. Rhyolithic lava (acidic) lava
Characteristics of basic lava
- upward movement of mantle material at constructive margins
- along spreading ridges and hot spots
- low in silica, mostly fluid lava which allows gas bubbles to expand and pop so it isn't explosive
Characteristics of andesitic lava
- destructive plate margins
- high in silica; very viscous (acidic)
- often solidifies before reaching surface; build of pressure creates violent eruptions
- gas can't escape so eruptions are explosive
Characteristics of rhyolithic
- destructive and collision
- same characteristics as andesitic