Chapter 4 Flashcards
What is Volcanism
When magma makes it way to the earth’s surface.
Vocanoes
landforms formed by the extrusion of lava or the ejection of rock fragments from a vent.
Explosive Eruptions
Also called pyroclastic eruptions long story short they erupt violently.
Effusive Eruptions
Eruptions dominated by lava flows.
How was the atmosphere created
By degassing magma during the time following Earths formation.
What is VEI an acronym for?
Volcanic Explosivity Index
viscosity
Does it flow like corn syrup? If yes then it has a high viscosity.
what are the three factors in lavas viscosity?
- The amount of silica it contains. 2. The temperature. 3. The amount of gas dissolved in magma.
How silica rich are Felsic rocks?
High usually 65% or more. Examples include rhyolite.
How silica rich are Mafic Rocks?
Low usually about 50% Basalt is a common Mafic Rock.
How silica rich are Intermediate rocks?
usually between felsic and mafic rocks 50%-65% silica.
Vent
The opening through which an eruption takes place
Crater
A basinlike depression over a vent at the summit of a volcanic cone. Material is not always ejected from the central vent.
What is a flank eruption?
Lava pours from a vent on the side of a volcano.
What are Effusive Eruptions classified by?
The lava flow.
pahoehoe
The skin cools on lava and it looks ropy or billowy surface. Kind of like fat roles think jabba the hutt.
spatter cone
a small steep sided cone built from lava sputtering out of a vent.
What is a Lava Tube?
A tunnel like conduit for lava to flow.
Flood basalts
A vast outpouring of lava over a large area with multiple lava flows. It kind of looks like a wetland for lava.
Columnar Jointing
Volcanic rocks in parallel, usually vertical columns, mostly six-sided; also called columnar structure.
Pillow structure
Pillow structure is formed when lava erupts into water.
Pyroclastic Flow
A mixture of gas and pyroclastic debris that is so dense that it hugs the ground as it flows rapidly in low areas. Think of a flash flood.
what are the 3 different types of volcanoes?
- Shield 2. Cinder Cone 3. composite.
How are Shield Volcanoes constructed?
Broad, gently sloping cone constructed of solidified lava flows. Think of captain Americas shield.
What is a Cinder Cone constructed of?
A volcano constructed of pyroclastic fragments ejected from a central vent. commonly have a slope of about 30 degrees. also known as pumice cones.
Composite Volcano
Constructed of Alternating layers of pyroclast and lava flow.
Circum-Pacific belt
Major belt around the edge of the pacific ocean on which most composite volcanoes are located and where many earthquakes occur.
What are Lava Domes.
steep-sided dome-or spine-shaped mass of volcanic rock. Usually formed from highly viscous lava that does not flow very far before it solidifies.
What is a Caldera?
A volcanic depression much larger tan the original crater having a diameter of at least 1 kilometer. Crater Lake is an example of this.
What is midigation
Reducing the impact of volcanic eruptions.
What likely killed the people in Pompeii
Hot pryloclasts.
Lahars
Really intense flash floods, but like on the river scale.
Active volcanoe
A volcano that is either currently erupting or has erupted recently.
Dormant or extinct volcanoes.
Volcanoes that have not erupted in a very long time.
What is the earliest notifying feature that a volcano is going to explode?
Increased seismic activity.
What are the only conditions that mantle rocks melt?
Decompression melting and flux melting.
convergent boundaries and volcanoes
Traditionally the volcanoes are composite in construction and the most known volcanoes are composite.
Where do volcanoes that form away from plate boundaries form from?
Hot spots or plums from the earth’s core.
What are the three most deadly volcanic hazards?
- Tsunami 2.Pyroclastic Flows 3.Famine and other indirect effects.
What are the three components of lava?
- Crystals 2.Molten silicate rock 3.Gases
