Igneous rocks- magma Flashcards
what is lava?
molten rock that has reached the earth’s surface
What is magma?
molten rock that is stored in the earths crust
when does the mantle melt?
Decompression melting
addition of Volatiles
rising magma comes in contact with other rocks and melts them
what is decompression melting?
the pressure on rock is reduced
what are volatiles?
substances that evaporate quickly and exist as gas at the surface of the earth (h2O, Co2, N2, H2, SO4) that weaken bonds lowering melting temperature
what is assimilation?
block of rock falls into magma and melts
what is contamination?
partial melting of rock mixes with magma from below
where does magma come from?
convergent boundaries
divergent boundaries
hot spots
how does magma come from convergent boundaries?
sea water stored in crust is released
water released from hydrous heats up
melting from overlying mantle due to addition of volatiles
how does magma come from convergent boundaries?
hot rocks rise
pressure drops
decompression melting
how does magma come from hot spots?
hot rock rises
pressure drops
decompression melting
what types of magma exists?
felsic
intermediate
mafic
ultramafic
what factors affect magma composition?
composition of the source rock
partial melting
crystal settling
what is a source rock?
the rock that melted
what is partial melting?
only 2-30% of a rock melts before magma migrates away
characteristics of partial melting?
minerals with higher silica content have lower melting temperatures
higher silica content is extracted first
residual rock is more mafic that the source rock
what is crystal settling?
mafic minerals form first and settle out of the melt forming a cumulate
residual melt is more felsic
mafic crystals are denser and fall to bottom
what is magma mixing?
magmas mixing with different compositions
causes chemical composition to change
what affects the rate of cooling?
depth of the magma
size and shape of the magma body
the presence of ground water
depth of magma in cooling?
the closer the magma is to the surface the faster it cools
size and shape of magma body in cooling?
the more surface area the body has the faster it looses heat
the surface area to volume ratio increases as size decreases
the presence of ground water in cooling?
water passing through magma absorbs heat and carries away heat, cooling off the magma faster
