Flashcards in Volcanoes Deck (22):
What is a volcano?
-Occurs when molten magma forces its way up to the Earth's surface either through a vent or through a fissure.
What does a vent eruption lead to the creation of?
What do fissure eruptions lead to the formation of?
Of a wider and flatter plateau
Upon reaching the surface, what is magma called?
What causes volcanoes to erupt?
-As magma rises, gasses dissolved in the magma expand.- Forces the magma upwards
-When magma reaches groundwater near the surface, the volcano becomes like a pressure cooker
-Volcanic mountain bulges- expanding gasses push through cracks in the volcano
-When they reach the surface, pressure is released, the bubbles expand and the volcano erupts
How many types of lava is there?
Name the two types of lava.
Name 4 different examples of volcanic material.
2. Pyroclasts + pyroclastic flows
3. Poisonous gases
4. Water vapour
Describe basic lava.
-Lower silica content (<55%)
-Fluid and runny, few trapped gases
-Extremely hot 1200 degrees
Is basic lava explosive?
No, it causes very gentle eruptions
Where is basic lava usually found?
Divergent plate boundaries and hotspots
What landforms does basic lava create?
Gently sloping volcanic landforms
Describe acidic lava.
-High silica content (>70%)
-Highly viscous/sticky/thick = lots of trapped gases
-Less hot 800 degrees
Where can acidic lava be found?
Convergent plate boundaries at subduction zones
What landforms does acidic lava form?
Forms steep sided volcanoes
What are pyroclastic flows?
Are boiling clouds of ash and rock which travel at speeds of up to 600 km/hr.
What is another name for pyroclastic flows?
How is pumice created?
When lava mixes with air, causing it to fill with air bubbles
Name some volcanic gases.
Name three extrusive volcanic landforms.
Central vent eruptions/volcanic cones
What does plutonic mean?
Volcanic landforms that were created beneath the Earth's surface.