Volcano Test Flashcards
What are the 5 types of Tephra(pyroclastics)
Ash cinders, lapilli, bombs blocks
What are the 3 gases that come from volcanoes
Water vapor (70-90%)
Carbon dioxide
Sulfur (stinks)
What are the 3 types of lave
Pahoehoe
AA
Pillow
Sizes if tephra small to big
Ash - less than 2mm like dust
Bombs - up to 1 meter across, ejected as liquid but hardens in the air
Blocks - can weigh several tons and is the largest
Pahoehoe lava traits
- Highly fluid/moves quick
- Congealed skin molds into billowing or ropy looking surfaces
- Very hot
- low viscosity
AA Lava
Rough and jagged blocks
Thick lavas press forward with a brittle crust
Cool temps
Pillow lava
Rounded like a pillow with a hard crust
Cooled underwater
What does a higher gas content in lave mean?
It’s more explosive
What are the 3 types of volcanoes
Shield, Composite, Cinder Cones
What is viscosity
Resistance to flow. Something that is less fluid and slow has a high viscosity. Something smooth and fluid has a low viscosity
How is viscosity affected
Temperature and composition
What is the composition of a volcanoes
Silica content , Felsic or mafic
How does temperature affect the viscosity of a volcanoes
Higher temps are less viscous meaning they flow faster and more fluid
How does silica affect a volcanoes viscosity
Felsic - high silica and high viscosity (it stiffer and less fluid)
Mafic - low silica and low viscosity
Is Felsic high or low silica
High
Is mafic high or low silica
Low
What controls the shape of a volcanoe
Composition of the volcano and temperature
Characteristics of a Shield Volcano
Broad, flat slope Layered lava / quiet eruption Basaltic (mafic) magma Low viscosity Mount Kea Hawaii and Belknap in the cascades
Characteristics of Cinder Cone volcano
Felsic with high gas content High viscosity Small with a steep side Lava butte in Oregon Made of layered tephra Explosive w/tephra ejected to make a cone shape
Characteristics of a composite volcano
These make up the largest percent of the earths volcanos (60
Percent)
andestic magma , medium to high viscosity
Large 20,000 feet high
Mt Hood
Alternative layers of lava and tephra. Can be quiet and very explosive
What are tools a scientist uses to predict or forecast volcanic eruptions
Seismic (earthquake activity) Increased gas (CO2 and sulfur) Deformation - physical changes like buldging Increased snow melt(heat) Rock analysis
What are cinder come volcanos made up of?
Tephra
Is AA lave high or low viscosity
High (moves slow)
Is Pahoehoe lava high or low viscosity
Low (it’s fluid)
What is crater lake
A caldera
What type of lava and magma is underwater
Pillow and Basaltic
Is a lava flow a hazard?
Yes it can destroy everything in its path
Are tephras a hazards
Yes if people are close to the volcano. Larger blocks and bombs flying out, ash near crops and livestock or ever airplanes
What is a Lahar
A volcanic hazard that is a debris flow of mud, rocks and water, this can kill the most people and is the
Most dangerous
What are lava domes
Volcano hazard Created when very viscous magma builds up and creates and unstable slope
What is a pyroclastic flow
High speed avalanche of gas, rock and hot ash during and eruption or when a lava dome collapses
Are gases a volcanic hazard
Yes carbon dioxide and sulfur are dangerous . Carbon dioxide can suffocate humans and animals, sulfur can create acid rain and is an ozone destroyer
How does viscosity affect gas content
High viscosity traps gas and is explosive and low viscosity releases gas and it a mellow eruption
How was crater lake formed
It’s a caldera and was formed when a Mount Manama volcano erupts and there is an empty space in the magma chamber and the volcanic cone collapses leaving a crater
What is a crater
Smaller than a caldera
What is a Felsic eruption
High silica , high viscosity, lots of trapped gas and very explosive
What is a mafic eruption
Low silica, low viscosity, not a lot of gases and non violent eruption
Mount Hood
Last erupted in 1805, eruptions of growth and lava domes, most likely scenarios is the collapse of lava dome near crater rock that would cause pyroclastic flows and lahars
Mount Rainier
Most dangerous volcano in cascades , large lahars of ice and snow could kill lots of people in the area
South sisters
Last erupted 2,000 years ago, it was bulging at the base but nothing now
Mount Bachelor
Poses little threat erupted 8-10,000 years ago
