Tsunamis and Volcanoes Flashcards
How would you describe a tsunami?
Wave or series of waves caused by the displacement of a large volume of water
What causes a tsunami?
Seismic activity, landslides, volcanic eruptions
What happens when a tsunami wave reaches land?
water depth decreases, wave speed decreases, wave height increases
What are the impacts of a tsunami?
Destruction of land and infrastructure, injury and death, contaminated drinking water, disease, economic impacts
Tsunami warning system?
Did not exist in the Indian Ocean in 2004; DART (Deep-ocean Assesment and Reporting Tsunamis)
How do we reduce tsunami impacts?
Warnings/bulletins if tsunami detected, warning signs, bioshields (vegetation acts as barrier between tsunami and infrastructure)
What is DART?
Deep-ocean Assessment and Reporting Tsunamis; Pressure sensor detect tsunami passing above
What is a volcano?
Opening in the earth’s crust through which lava, volcanic ashes, and gases escape
What is lava?
molten rock that breaks through earth’s surface
What is magma?
molten rock underground that contains dissolved gases
What is being erupted at mid-ocean ridges?
basalt
What is being erupted above hot spots?
basalt
What is being erupted at subduction zones?
andesite
What is being erupted as magma moves up through crust?
rhyolite
Each rock type has different silica content: What does high silica content entail?
High viscosity
What type of lava flows are there?
a’a, blocky, and pahoehoe
What is the texture and viscosity of a’a flow?
rubble-like texture, broken blocks, high viscosity
What is the texture and viscosity of pahoehoe flow?
smooth ropy texture, low viscosity
What is the texture, viscosity, and rock of blocky flow?
Large angular blocks, steep flow fronts, usually andesitic or basaltic andesitic, higher viscosity
What characterizes basalt magma?
fine-grained, mafic igenous rock characterized by lower viscosity and lower gas content
What characterizes andesite and rhyolite magma?
Increasing silica content, usually melting subducting plate, blocky lava flows
How does basaltic, andesitic, and felsic lava flow?
B: Low viscosity and can flow long distances
A: Too viscous to flow far and tends to break up as it flows
F: So viscous may pile up in a dome-shaped mass
Volcano type is partially dependant on magma viscosity - reflected in rock type: what are the four volcano types?
Shield volcano, composite or stratovolcano, volcanic dome, cinder cone
What are the four rock types associated with each volcano?
Shield volcano: Basalt
Composite or stratovolcano: Andesite
Volcanic dome: Felsic
Cinder cone: Basalt
