Plate tectonics Flashcards
What is a volcano?
Opening in Earth’s crust that releases lava and other pyroclastic materials
Define magma.
Molten rock material under the surface
Define lava.
Molten rock on the surface
What are the types of volcanic rock based on silica content?
- Mafic
- Felsic
What is the silica content of mafic rocks?
Low
What is the silica content of felsic rocks?
High
How do mafic and felsic rocks differ in movement?
- Mafic: Fast
- Felsic: Slow
What are the types of volcanic eruptions?
- Gentle
- Explosive
- Very explosive
What is pahoehoe lava?
Ropey looking lava formed from fluid strands of molten lava
What is aa lava?
Jagged looking lava
What gases are commonly found in magma?
- Water vapor
- Carbon dioxide
- Sulfur
What is the relationship between gas content in magma and eruption type?
High amount of gas = explosive eruption
Define tephra.
Any solid fragment ejected during a volcanic eruption
What are the three types of tephra based on size?
- Ash: Smallest
- Lapilli: Medium
- Blocks/Bombs: Largest
What is a pyroclastic flow?
Dense superheated cloud that travels downhill with amazing speed (450 mph)
What is a lahar?
Hot ash mixed with snow and ice on a volcano forming a fast-moving mudflow
What are the three phases of a volcano?
- Active: erupting or providing heat
- Dormant: sleeping
- Extinct: never erupts again
What type of volcano is formed at divergent boundaries?
Shield volcano
What is the shape and eruption type of a cinder cone volcano?
- Cone shape
- Steep sides
- Narrow base
- Explosive eruption
What type of volcano is a composite (strato) volcano?
Alternating layers with explosive eruptions
What is a pillow lava?
Underwater formation at divergent boundary
What is columnar jointing?
6 sided formation in volcanic rock
What is a caldera?
Crater-shaped basin formed when a large volcano collapses
What are hot spots in volcanology?
Volcanic activity in the middle of lithospheric plates
What are igneous intrusions?
Formed by magma cooling beneath the surface
What is a dike?
Vertical igneous intrusion that cuts across existing rock layers
What is a sill?
Igneous intrusion parallel to the rock layers it intrudes
What is a laccolith?
Dome-shaped igneous intrusion
What is a batholith?
Largest type of igneous intrusion, forming the core of many mountains
What is a volcanic neck?
Remains of an extinct volcano
