Please enable JavaScript.
Coggle requires JavaScript to display documents.
volcanoes, : - Coggle Diagram
volcanoes
-
Found
-
Broken into extremely large slabs called tectonic plates and earths surface is divided into 7 of these plates.
Volcanoes are found where these plates meet, which are called plate boundaries.
75% of the earths active volcanoes are in the ring of fire which circles the edges of the pacific ocean.
-
Eruptions
Slow moving - high viscosity of magma, low dissolved gas, slow-moving lava, effusive with slow moving lava that piles up.
Explosive eruptions - high viscosity of magma, high dissolved gas, lava explodes out of the volcano, explosive eruption with hard pyroclastic material.
Lava flows - low viscosity of magma, low dissolved gas, fast-moving streams of lava, effusive with highly fluid lava flows.
Fire Fountains - low viscosity of magma, high dissolved gas, fire-fountain spewing lava into the air, explosive with fluid lava.
-
Form
Island arc occur when one plate descends or subducts, under another plate
Spreading centers- plates move away from each other, decreasing the pressure on the underlying mantle, allowing it to rise and melt, forming lava
Continental arc - two plates come together and one of the plates may slide under another in a process called subduction.
-
Types
Composite- steep-sided, symmetrical cones formed when pyroclastic eruptions alternate with lava flows and layers that were built up over time.
-
Cinder cone- relatively small, steep, cone-shaped hills made up mostly of partly burned ash and lava cinders
-
-
-