intrusive and extrusive igneous rocks els

magma

molten rock beneath earth’s surface

-flows out from underground deposits and magma chambers

igneous rocks

extrusive and intrusive rocks

extrusive rocks

magma that reaches the surface and erupts

-derives from magma that rises from depths of 200km to 70km

-forms when lava cools

intrusive rocks

known as plutonic rocks; magma that accumulates and hardens underneath the surface

-found in spaces and fissures in the surface

Crystallization

The solidification of magma

batholith

a huge magma deposit

stock

similar to a batholith but smaller

dike

magma that forms an elongated wall

sill

flat layer of magma beneath the crust

laccolith

a sill that gathers enough magma to create a dome

pipe or plug

magma that stays within a volcano’s passage

xenolith

rock fragment introduced from elsewhere and of different composition that becomes embedded magma

tephra

fragments of rock violently thrown out of a volcano

-general term for all pyroclastic fragments of different sizes

viscosity

the way lava flows is determined by this

-the measure of a fluid’s resistance to flow

-depends on the type of magma > chemical composition > silica is the main component of magma

lava with low viscosity and high temps:

flow and spread easily over long distances

lava with high viscosity and low temps:

very thick and does not flow easily

pahoehoe

geologists refer to low viscosity lava

aa

geologists refer to high viscosity lava

types of magma

rhyolithic - high viscosity,

andesitic,

basaltic - low viscosity

The more/higher silica, lava is thicker and flows more slowly >explosive eruption

The lesser silica, lava is runny and flows easily >gentle eruption

how is silica content related to the viscosity of lava?

pyroclasts

term for rock fragments when expelled from volcano

bombs and blocks

-shot as projectiles at 75 to 250 m/s, fall near the source

-large tephra

lapilli and ash

will reach farther from the source as they are lighter materials.

-particles smaller than 0.01mm can stay in the atmosphere for 2-3 years

cooling time

the factor that determines crystal size

igneous rocks

form when melted rock cools n hardens

ex. extrusive and intrusive rocks

sedimentary rocks

form when sediments pile up, get compacted and cemented together

keyword: layers

Metamorphic rock

form when existing rocks change due to heat and pressure

cubic, hexagonal, orthorhombic, tetragonal, monoclinic, and triclinic

six basic crystal structures

extrusive -smaller crystals due to faster cooling

intrusive -larger crystals

between extrusive and intrusive rocks, which have bigger crystals?