molten rock, suspended minerals and gases
magma is a mixture of
wet minerals and rocks melt at _______ temperatures than do dry minerals and rocks
As pressure increases, the temperature that dry things melts _______
pressure, temperature and water content
Three things that affect formation of magma
Because the pressure increases the melting temperature
why isn't Earth's mantle liquid?
it's present in the pore spaces of some rocks and can be bound in the crystal structure of some minerals
How is water present in rocks and minerals?
Magmas are named after _________rocks
Basaltic magma forms when rocks in the _______mantle melt
1 small.......2 low......3 quiet..
Basaltic magma contains__1___ amounts of silica and has __2___ viscosity and fuels relatively ____3__eruptions
Andesitic magma fuels volcanoes with_______ eruptions
1silica 2 intermediate
Andesitic magma contains about 60%___1___ and has ____2____viscosity
oceanic crust and sediments
Andesitic magma forms from __________ and _______
Rhyolitic magma forms beneath _______crust
Rhyolitic has the_____silica content of all
Rhyolitic magma has the same composition as_______
1 viscosity 2 slowly
Rhyolitic magma has high__1____ and flows ___2___
Rhyolitic magma produces very ________ volcanoes
viscosity increases with a decrease in temperature
How does the viscosity of magma change as magma cools?
It flows less quickly
Does cooler magma flow more or less quickly than hotter magma?
magma high in silica has a higher viscosity than magma low in silica
Is the viscosity of magma that is high in silica higher or lower than magma that is lower in silica?
basaltic lava flows faster because basaltic lava has less silica
Which type of lava-basaltic lava or rhyolitic lava-flows faster? Explain.
intrusive igneous rock body
what is a pluton?
pluton that is parallel to the rocks it intrudes
what is a sill?
a mushroom shaped pluton
what is a laccolith
irregular shaped pluton that is like a batholith but smaller
what is a stock?
pluton that cuts across preexisting rocks
what is a dike
what is responsible for the formation of many plutons?
opening where lava erupts from
the depression around the vent
rock pieces thrown in air during eruption
smallest tephra is...
tephra that is larger than dust
fast moving clouds of ash, gas and other tephra
forms when part of the volcano collapses into the magma chamber
large, angular volcanic fragments are called
large, rounded or streamlined tephra are called
most of the world's volcanoes form along_______plate boundaries
locations of most convergent boundary volcanoes
circum pacific belt marks...
western coasts of N and S America and down the eastern coast of Asia
circum pacific belt stretches along the
slabs of oceanic crust descend into mantle and melt; magma that forms is forced upwards and volcanoes form
how do volcanoes form?
___________ forming as a result of a hotspot
1 high temperature plumes melting the rock which causes magma to move upward and cause volcanoes
2 from the formation of flood basalts (outpourings of basalt lava) which erupt from fissures to form a flat plain or a plateau instead of volcanic mountains
hot spots can forms from_____1____and ______2_____
at______ _____ boundaries, magma squeezes through cracks and forms mountains
under water along ocean ridges
most volcanoes that are formed along divergent plate boundaries are___________
divergent plate boundary activity can be observed in _______
-composite volcano-in between cinder and shield, forms with layers of tephra and lava, has lots of silica, water and gases, most dangerous type of volcano
-cinder-cone volcano-small and steep, formed from tephra being thrown in air and then piling up around vent, lava has higher silica and water than shield volcanoes but still not a lot, contains a large volume of gases
-shield volcano-really big and sloped, lava has small amounts of gas and silica, forms when layers of basaltic lava accumulate during a non-explosive eruption
3 types of volcanoes