Earth Science: Volcanoes Flashcards
What is a volcano?
Mountain formed from lava and pyroclastic materials
What are pyroclastic materials?
Ash and lava fragments
What is a crater?
Depression at summit of volcano.
What is a vent?
Opening that supplies magma from source to top of volcano.
What is a conduit or pipe?
Carries gas-rich magma to Earth’s surface.
What is a magma chamber?
Large pool of liquid rock beneath Earth’s crust.
What is the difference between magma and lava?
Magma is molten rock underground, lava is molten rock expelled from volcano.
What are the three types of volcanoes based on shape?
Composite, cinder cone, and shield volcano.
What is the other name for Composite?
Stratovolcanoes
What is a composite (stratovolcano)?
Large cone-shaped volcano composed of alternating lava flows and pyroclastic materials, typically found near the Pacific Ocean, and known for being the most violent type.
What is an example of a composite (stratovolcano)?
- Mt. Mayon
- Mt. Pinatubo
- Mt. Fuji
- Mt. St. Helens
What is a cinder cone (scoria cone)?
Small and simple volcano made of pyroclastic materials from single vent, w/ steep slopes and often occurring in groups.
What are cinder cones also known as?
Scoria cones
What is an example of a cinder cone (scoria cone)?
- Taal Volcano
- Mt. Paricutin
In which country is Mt. Paricutin located?
Mexico
What is a shield volcano?
Broad, gently sloping landform made of low-viscous basaltic lava flows that can have gentle eruptions.
What is the composition of shield and cinder cones?
Basaltic
What is the composition of composite cones (stratovolcanoes)?
Andesitic
What is the composition of pyroclastic flows and volcanic domes?
Rhyolitic
What is the factor 1 affecting the violence of volcanic eruptions?
Composition of the Magma
What is the factor 2 affecting the violence of volcanic eruptions?
Temperature of the Magma
What is the factor 3 affecting the violence of volcanic eruptions?
Dissolved Gases in the Magma
What is the factor 4 affecting the violence of volcanic eruptions?
Viscosity
What are the main components of dissolved gases in magma and what do they do?
Main Components of Dissolved Gases in Magma:
- water vapor
- carbon dioxide
They provide force to extrude lava.
What is Viscosity?
Measure of resistance of material to flow.
What is the relationship between temperature and viscosity in magma?
Hotter magmas are less viscous
How does viscosity of magma relate to its composition?
The viscosity of magma is related to its composition, with high silica content having high viscosity (e.g. Rhyolitic Lava) and low silica content being more fluid (e.g. Basaltic Lava).
How does viscosity affect volcanic eruptions?
Viscous magma results in a more violent eruption.
What is a Pahoehoe Lava Flow?
Smooth liquid type of lava flow that resembles rope braids.
What is an Aa Lava Flow?
More viscous type of lava flow w/ rough and jagged blocks.
Fragments ejected during a volcanic eruption, ranging from fine particles and ash to large pieces weighing several tons.
Pyroclastic Materials
What are ashes and dusts in a volcanic eruption?
Fine and glassy fragments
What is pumice?
Frothy and air-filled lava
What are cinders in a volcanic eruption?
Pea-sized particles
What are lapilli in a volcanic eruption?
Walnut-sized particles
What are volcanic blocks?
Hardened lava that are larger than lapilli.
What is a volcanic bomb?
Ejected hot lava, larger than lapilli, that can travel a short distance and start fire.
What is a crater in a volcanic eruption?
Results from explosions of material out of vent and collapse of material back into vent
What is a caldera in a volcanic eruption?
Large depressions, nearly circular shape, formed by collapse of magma chamber in volcano
What are lava plateaus?
Formed by large bursts of lava that solidify and build up layer upon layer over time
What causes rocks in the mantle to melt and form magma?
Increase in temperature or decrease in pressure
What is a factor in the formation of active volcanoes?
Movement of tectonic plate boundaries, particularly Pacific Ring of Fire where 75% of active volcanoes in world are found.
What causes a volcano to erupt?
Increase in temperature or decrease in pressure in mantle leading to formation of magma, and movement of tectonic plate boundaries, particularly in Pacific Ring of Fire.
How do volcanologists predict volcanic eruptions?
By measuring small earthquakes, slope changes with a tiltmeter, outflow of volcanic gases, and changes in temperature from orbit.
How do volcanologists predict volcanic eruptions by measuring earthquakes?
By monitoring increases in number and intensity of small earthquakes before an eruption.
How do volcanologists predict volcanic eruptions by measuring slopes?
By using a tiltmeter to detect bulges that may form due to the buildup of magma.
How do volcanologists predict volcanic eruptions by measuring volcanic gases?
By monitoring changes in the outflow of volcanic gases such as sulfur dioxide and carbon dioxide.
How do volcanologists predict volcanic eruptions by measuring temperature?
By observing changes in temperature over time from orbit.
