2.2 plate tectonics Flashcards
where is the vent located in a volcano?
central opening to the volcano on Earth’s surface
where is the crater?
cuplike hollow around vent
what and where is a caldera in a volcano?
when volcano collapse, it forms a very wide crater
what is lava?
magma that has reached the surface
where is magma chamber located at?
where magma is located
how do tectonic process result in volcanic eruption?
when lava erupts onto the Earth’s surface. It may form a cone-shaped mountain as more lava erupts and accumulates over time
formation of volcanoes at divergent boundaries (O-O)
- plates move part, the crust stretches and fractures develop
- the decrease in overlying pressure causes parts of underlying mantle to melt, forming magma.
- magma contains dissolved gases and is less dense than the surrounding materials
- magma rises through weak areas in crust to earth’s surface to erupt as lava, causing volcanic eruption
- the lava cools, solidifies & accumulates over time, forming a volcano
formation of volcanoes at convergent boundaries (C-O)
- plates move towards each other and denser plate subducts under the other
- as the subduction plate sinks into the mantle, the high pressure forces water out of oceanic crust.
- water lowers melting point of overlying mantle, causing it to melt, forming magma
- magma contains dissolved gases and is less dense than surrounding materials
- therefore, magma rises through weak areas in the crust to Earth’s surface to erupt as lava, causing a volcanic eruption.
- lava cools, solidifies and accumulates over time, forming volcano
why are some volcanic eruptions more explosive?
due to how easily dissolved gas can escape from magma. Low-silica lava has low viscosity while high-silica lava has high viscosity.
characteristics of high silica magma
- more vicious magma
- does not allow dissolves gas from escaping easily
- more pressure builds up until gases escape easily
- violent ; explosive eruption
- associated with stratovolcanoes
(example: mount merapi; stratovolcano, not explosive, viscous magma rose in a way that allowed dissolve gas to escape easily )
characteristics of low silica magma
- less viscous magma
- allow dissolved gas to escape easily
- less pressure builds up
- gentle, effusive eruptions
- associated with shield volcanoes
how does stratovolcanoes form?
- high silica magma rises through weak areas in the crust to the Earth’s surface and erupts explosively as lava, ash and rocks
- the ash and rocks settle on the sides of the volcano an are later covered by lava
- over successive eruptions, a tall volcano consisting of alternating layers of ash and lava develops
- As the highly viscous lava travels a shorter distance before cooling & solidifying, the volcano has steep sides and a narrow summit.
what are the characteristics of stratovolcanoes?
tall, conical in shape
made of alternate layers of high silica lava and ash
example: mount pinatubo
danger threats: rock fragments, heated gas, violent eruptions
how does shield volcanoes form?
- low silica magma rises up through weak areas in Earth’s crust such as fracture to Earth’s surface and erupts effusively, as fluid lava.
- over successive eruptions, a volcano consisting of lava develops
- as the les viscous lave travels a longer distance before cooling and solidifying, the volcano has gently sloping sides with a broad summit.
what are the characteristics of shield volcanoes?
short, gentle-sloping, flat on top of
made of low silica lava
example; mount washington (USA)
threat/ danger: hot lava
