Volcanoes. 7.2 Volcanic Eruptions Types of Lava Mafic Lava: rich in magnesium and iron – Forms...
-
Upload
antonia-ball -
Category
Documents
-
view
216 -
download
2
Transcript of Volcanoes. 7.2 Volcanic Eruptions Types of Lava Mafic Lava: rich in magnesium and iron – Forms...
Volcanoes
7.2 Volcanic Eruptions
Types of Lava• Mafic Lava: rich in magnesium and iron– Forms much of the oceanic crust
• Felsic Lava: rich in silica (less magnesium and iron)– Forms much of the continental crust
What determines the type of Volcanic Eruption?
Composition of lava (mafic or felsic ) determines the type of eruption.
• Mafic Lava- hot and thin, flows similar to water– Creates quiet eruptions
• Felsic Lava- thick, viscous and cooler. Contain large amounts of trapped gasses. These gasses boil out explosively. – Creates explosive eruptions– Pyroclastic Material: rock fragments ejected into the air
Journal
• Which lava flows easily creating quiet volcanic eruptions?
• Which lava erupts violently?
Pyroclastic Material Classified based on size:
• Lapilli- less than 64 mm in diameter• Volcanic ash – less than 2 mm in diameter• Volcanic dust – less than 0.25mm in diameter
Types of Volcanoes
• Shield• Cinder-Cone (or Dome)• Strato-volcanoes or composite volcanoes
Shield Volcanoes
• Broad base and gentle sloping sides• Formed by mafic lava
Cinder-Cone Volcanoes
• Steep slopes • Formed by felsic lava
Strato-volcanoes (or composite volcanoes)
• Formed by both smooth lava flows and explosive pyroclastic eruptions
• Form high volcanic mountains
1. Create a quick sketch of the following Volcanoes.2. Name each Volcano type.
Craters and Calderas
• Crater: funnel shaped pit• Caldera: large depression that occurs when a
volcanic cone collapses
Predicting Volcanic Eruptions
• seismographs monitor small earthquakes– number of earthquakes increases prior to volcanic
eruptions
• slight bulging of the surface of the volcano
• composition of gasses given off by the volcano
Journal:
What might an increase in earthquakes near a volcano indicate?
7.3 Volcanoes not on Earth!!!
The moon: Basaltic lava flow on the near side of the moon
• No tectonics or convection currents….. so how could the volcanoes have formed….• May have been caused by intense heat due to meteorite collisions
Mars: Seismically active and Crust is not shifting, produces very large volcanoes
• These volcanoes may still be active.
Io: moon of Jupiter, has active volcanoes. The lava is sulfur based.
• The cause of its warm core is the friction as its surface is pulled back and forth
due to gravitational pull from theother moons and Jupiter.
The End