Unit 7 Volcanoes, Igneous Rocks & Earthquakes 24-25

a'a

a high viscosity lava flow with a rough, jagged surface composed of broken lava blocks called clinkers

intermediate (andesitic)

composition of magma/lava with an even mix of silica, magnesium and iron

ash

smallest pyroclastic less than 2mm in diameter

mafic (basaltic)

composition of magma/lava with a low silica and gas content high in iron and magnesium which will be low in viscosity.

caldera

a large bowl shaped feature caused by the collapse of a volcano/surface after the magma chamber erupts and empties

cinder cone volcano

small volcanos built from pyroclastic material. A product of relatively gas-rich magma. They are very steep and have large craters.

clinkers

broken lava blocks that fall down the front of an A'a flow

coarse-grained

Intrusive igneous rock texture showing large crystals, formed from magma which cooled slowly.

extrusive igneous rocks

fine-grained, glassy or vesicular igneous rocks that form from lava cooling rapidly at surface

fine-grained

extrusive igneous rock texture of very small crystals, often too small to be seen without a microscope, that forms from lava cooling fast.

intrusive igneous rocks

coarse grained igneous rocks that form from magma cooling slowly underground

kipuka

A small piece of land that is completely surrounded by lava flows

lahar

A lahar is a mudflow composed of a slurry of pyroclastic material & water

lapilli

second smallest pyroclastic, usually vesicular, between 2mm-64mm in diameter

lava

liquid rock that has reached the surface and erupted from a volcanic vent.

lava block

Pyroclastic that is bigger than 64mm, solid irregular shaped piece of side of volcano

lava bombs

Pyroclastic that is bigger than 64mm, Ejected from a volcano while molten that takes on "football" shape as it cools in air

lava lake

a pool of lava that has collected in a crater or a caldera

lava trees

Lava surrounds the tree and cools on contact, leaving pillars of igneous rock once the lava flow drains away

lava tubes

A tunnel within a lava flow created where lava travels as a river of lava under the solidified surface.

magma

liquid rock located under ground

pahoehoe

a low viscosity lava flow that has a smooth (yet often wrinkled) surface

Pele's Hair

A delicate strand of volcanic glass, gold in color, created by wind blown lava

Pele's tears

a small, tear-drop shaped volcanic glass fragment created by lava splattering into air and cooling as it falls

pyroclastics

A general term for fragments of volcanic rock and lava that are blasted into the air (solid.)

pyroclastic flow

A ground hugging avalanche of hot pyroclastics and volcanic gas

flows down the side of the volcano at speeds of 100-430 mph and temperatures greater than 500° C

felsic (rhyolitic/granitic)

composition of magma/lava with a high silica and gas content low in iron and magnesium which will be high in viscosity

curtain of fire

lava eruptions from fissures

shield cone volcano

A volcanic cone with a large, broad base and gently sloped sides; results from effusive eruptions.

skylight

an opening in the roof of a lava tube

Stratovolcano (Composite Cone Volcano)

a large volcano with steep sides built of both lava flows and pyroclastics to form a classic triangle mountain shape

coarse texture

containing large crystals from slow cooling, characteristic of intrusive igneous rocks

very-coarse grained/pegmatitic

Mineral grains that are exceptionally large. The largest ones can be more than 3 cm long.

vesicular

texture of quickly cooled magma that contains a large amount of dissolved gasses that become trapped as bubbles

viscosity

a liquid's resistance to flow

volcanic explosivity index (VEI)

An intensity scale that rates a volcano's destructiveness and explosive power on the amount of matter it ejects during an eruption.

volcanism

the activity of magma forming and coming toward surface

volcano

landform created when magma reaches the surface through an opening in Earth's crust

felsic (granitic)

composition of magma that is high in silica and therefore has a high viscosity

vent

The opening through which molten rock and gas leave a volcano

conduit

a channel connecting a magma chamber to the vent for erupting lava

decompression melting

melting due to a drop in confining pressure that occurs as mantle rock rises

effusive eruption

An eruption that yields mostly lava, not pyroclastics.

explosive eruption

an eruption that yields mostly pyroclastics, not much lava

Pneumonoultramicroscopicsilicovolcanoconiosis

A lung disease caused by the inhalation of ash

crater

A bowl-shaped area that forms around a volcano's vent when a ring of eruption materials lands in a circle around it

geothermal gradient

the gradual increase in temperature with depth in the crust

Bowen's Reaction Series

the simplified pattern that illustrates the order in which minerals crystallize from cooling magma according to their chemical composition and melting point

partial melting

describes the incomplete melting of mantle rock due to different minerals in rock melting at different temperatures

magmatic differentiation

the formation of one or more magmas of differing composition from a single parent magma

crystal settling

During the crystallization of magma, the earlier-formed minerals are denser than the liquid portion and settle to the bottom of the magma chamber.

assimilation

Magma melting through lithosphere can incorporate this rock therefore change the magma composition.

magma mixing

one way the composition of a magma body can change through two magma bodies merging into one

batholith

A solidified magma chamber made of intrusive igneous rock

volcanic neck

hardened magma in a volcano's central conduit

seismograph

A device that records ground movements caused by seismic waves as they move through Earth

seismogram

the record of an earthquake's seismic waves

moment magnitude scale

A scale that rates earthquakes by estimating the total energy released by an earthquake

body waves

seismic waves that travel through the interior of the earth

surface waves

seismic waves that travel along the surface of the earth

Primary waves (P-waves)

a type of seismic body wave that cause particles in the ground to move in a compression-extension motion while transmitting the energy, similar to a coiled spring.

Secondary waves (S-waves)

a type of seismic body wave that cause particles in the ground to temporarily change shape while transmitting the energy, which can only happen in solids .

liquifaction

The process by which an earthquake's violent shaking suddenly turns loose soil and groundwater into liquid mud

Seismic Shadow Zone

Area where seismic waves aren't received from earthquake; P waves get refracted through the core; S waves don't travel through outer or inner core

Subsidence

a geological phenomenon in which the ground in an area sinks

tsunami

A giant wave usually caused by an earthquake on a megathrust fault on subduction boundaries.