Volcanoes Flashcards
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?
Cone-shaped mountain
What do fissure eruptions lead to the formation of?
Of a wider and flatter plateau
Upon reaching the surface, what is magma called?
Lava
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?
Two
Name the two types of lava.
Basic lava
Acidic lava
Name 4 different examples of volcanic material.
- Lava
- Pyroclasts + pyroclastic flows
- Poisonous gases
- 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
