ch. 8 volcanoes and plutons

Process forming magma

increasing temperature, decreasing pressure (—>”pressure-release melting”), addition of water

magma forming in spreading centers

decreasing pressure (ascending asthenosphere)

magma in mantle plumes

decreasing pressure; basaltic magma can create granitic magma under/in continental crust (through increasing temperature)

magma in subduction zones

addition of water is very important

what is the “ring of fire”?

a volcanic and earthquake-prone zone around the Pacific Ocean, with many subduction zones and spreading center

basalt

found in oceanic crust, dense, rich in iron and magnesium

granite

found in continental crust, less dense, rich in silica

process of partial melting

some minerals in a rock melt due to heat, creating silica-rich magma. it occurs in subduction zones, spreading centers, or mantle plumes

how old are continents and how may they have formed?

billions of years old, formed through plate tectonics and landmass collisions

behavior of magma: granitic

high in silica and water; low melting temperature

behavior of magma: basaltic

low in silica and water; higher melting temperature

behavior of magma: effects of silica, effects of water

higher silica lowers melting temp, makes magma more fluid

plutons

formed in crust, they’re large bodies of igneous rock that form when magma cools and solidifies beneath the earths surface

what are batholith?

large mass of intrusive rock

what are stock?

smaller version of a batholith

what are sill?

horizontal magma intrusion

what is a dike?

vertical magma intrusion

what is a fissure eruption and what kind of lava erupts?

lava erupts from cracks, often producing basaltic lava

what kind of shape and type of eruption does a shield volcano have?

its broad and non-explosive

what kind of shape and type of eruption does a cinder cone have?

it’s steep and explosive

what kind of shape and type of eruption does a stratovolcano have?

its steep and has a alternating eruption

what type of magma, succession of events do volcanic explosions have?

high in silica magma causes explosive eruptions, leading to calderas

what are calderas?

a large depression formed when a volcano collapses after a major eruption

possible effects of volcanic activity on global climate

insolation decline (cooling)

CO2 addition to the atmosphere (warming)