Types of Volcanoes Flashcards
Composite (Stratovolcano)
Composite volcanoes are made up of alternating layers of lava and ash (other volcanoes just consist of lava).
They are usually found at destructive or compressional boundaries.
The eruptions from these volcanoes may be a pyroclastic flow rather than a lava flow. A pyroclastic flow is a mixture of hot steam, ash, rock and dust.
High viscosity of lava
A pyroclastic flow can roll down the sides of a volcano at very high speeds and with temperatures of over 400°C.
What is the difference between acid lava and basic lava?
Basic lava comes from volcanoes formed at constructive boundaries while acid lava comes from volcanoes formed at destructive boundaries
Other types of destructive volcanoes
Tephra cone
Dome
Caldera
How are volcanoes formed at constructive boundaries?
As plates move apart, the magma rises upwards from the mantle to fill the gap. This adds new rock to the spreading plates. Some of the magma may also be forced out to the surface through a vent. Some volcanoes grow high enough to form volcanic islands.
How are volcanoes formed at destructive boundaries?
When the plates collide, the denser oceanic plate is subducted underneath the less dense continental plate and pushed into the mantle. Here, the plate melts and is destroyed in the subduction zone. The subduction zone and plate form a pool of magma. The great heat and pressure may force the magma along a crack where it erupts at the surface to build up a volcano.
Examples of shield volcanoes
Mauna Loa-Hawaii
Hekla-Iceland
Examples of composite volcanoes
Etna, Vesuvius-Italy
Sheild
Shield volcanoes are usually found at constructive or tensional boundaries.
They are low, with gently sloping sides.
They are formed by eruptions of thin, runny lava.
Eruptions tend to be frequent but relatively gentle.
High temperatures
Basalt rock type
