(H) Volcanoes and Igneous Rocks - Pavlik -2023

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A lava flow of basaltic lava that forms rough, jagged blocks. It forms when the lava has cooled down, thus increasing the viscosity.

andesitic (intermediate)

Igneous rocks with a composition between granitic and basaltic rocks. Associated with volcanic activity.

Aphanitic

fine-grained, salt and pepper sized

ash

Tephra less than 2mm in diameter

assimilation

The process where magma incorporates some of the surrounding rock as it migrates upward.

basaltic (mafic)

Igneous rocks with a substantial amount of dark-colored minerals (basaltic composition)

Batholiths

A very large intrusive igneous rock mass that has been exposed by erosion and with an exposed surface area of over 100 square kilometers.

block

Tephra that is bigger than 64mm, solid piece of side of volcano

Bombs

Ejected from a volcano while molten or semi-molten

Bowen's reaction series

The arrangement of minerals that shows at what temperatures they solidify at. Discovered at the beginning of the 12th century. Olivine is first to cool and quartz is last.

Caldera

a large crater caused by the violent explosion of a volcano that collapses into a depression

cinder cone

Volcanos built from ejected lava fragments (pyroclastic material). A product of relatively gas-rich mafic magma. They are very steep, have deep craters, and do not usually eject lava. 1000-1500 ft (small), mild eruptions, example : Paricutin, Mexico

Clinkers

broken lava blocks that fall down the from of an Aa flow

coarse-grained

Large crystals, formed from igneous rock which cooled slowly. Nerd-sized

Composite (Strato) Volcano

classic volcanic shape, taller than wide, layers, Made from felsic magma, high in quartz, high in viscosity, high in gas content, violent eruptions, Example: Mt. St. Helens, Fuji, Tambora

concordant

A descriptive word for plutons that form parallel to features such as sedimentary strata.

volcanic pipe

the conduit connecting the crater of a volcano with an underlying magma chamber

crater

A steep-walled depression on the summit of many volcanoes. They are formed when ejected fragments of the volcano collect around the vent.

crystal settling

A process that occurs when the earlier-formed minerals are denser than the liquid portion and sink to the bottom of the magma chamber.

crystallization

The process by which magma cools and solidifies. This may occur beneath the surface or after a volcanic eruption. The slower the process, the larger the crystals.

decompression melting

melting due to a drop in confining pressure that occurs as rock rises closer to the surface

dike

Tabular discordant plutons that are produced when magma is injected into fractures.

discordant

A descriptive word for plutons that are cut across existing structures.

extrusive (volcanic) igneous rock

rocks that form when molten rock solidify at the surface,

felsic

light in color, high in quartz and feldspar, generated by partial melting at subduction boundaries

fine-grained

The texture of igneous rocks that form rapidly at the surface. Crystals are thus too small to be seen.

Fissure eruption

the eruption of magma out of a crack in the lithosphere, rather than from a single pipe or vent

Geothermal Gradient

the gradual increase in temperature with depth in the crust.

glassy

The texture of igneous rocks that cool too quickly to form crystals.

granitic composition

igneous rocks composed of light colored silicates, also known as felsic

Harry Truman

Man who refuses to leave before Mt. St. Helen's eruption. he dies in his home by Spirit Lake and a song is made for him.

hornito

A spatter cone that forms on the surface of a lava flow and looks like a big drip-castle. It develops when lava accumulates around a vent in the ground. They typically have steep sides and form pinnacles.

Hot Spot

an area where material from deep within the mantle rises and then melts, forming magma

igneous rock

the rock resulting from the cooling and crystallized magma or lava

inclusion

the other name for the xenolith, when a different type of rock is incorporated into another plutonic rock

intrusive

igneous rocks that form at depth that are only exposed through uplifting.

Kipuka

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

laccoliths

Tabular concordant plutons that form when viscous magma is injected between sedimentary layers near the surface. It is dome-shaped.

lahar

Large composite cones generate this type of mudflow, which is saturated volcanic debris that moves down the steep volcano slopes. They can form in hard rainfall or when the volcano erupts and melts snow

lapilli

Tephra between 2mm-64mm in diameter and is vesicular

lava

hot molten (or semi molten) rock that has reached the surface. Most of the gasses have escaped

lava bench

A platform created by more recent lava flows that extend over the old shoreline. They often conceal loose material and are hazardous.

lava trees

Lava surrounds the tree but does not destroy it (leaves a column of rock.)

Lava tubes

A natural conduit where lava travels under the surface of a lava flow. The tubes form by the crusting over of lava channels. (generally pahoehoe lava)

mafic

igneous rocks high in Mg and Fe, dark colored, prevalent in ocean crust

magma

hot , molten rock located under ground made of a liquid (melt), solid portion (minerals)

magmatic differentiation

The formation of one or more secondary magmas from a single parent magmas.

melt

The liquid portion of the magma body. As this hardens, it forms crystals.

mush

the crystallized rock that is on the verge of being solid

Nuee Ardente

french word for pyroclastic flow means glowing cloud

obsidian

common type of volcanic glass, looks like dark glass

Pahoehoe

a hot, fast-moving type of lava that hardens to form smooth, ropelike coils

Partial melting

The process by which most igneous rocks melt. Since individual minerals have different melting points, most igneous rocks melt over a temperature range of a few hundred degrees. If the liquid is squeezed out after some melting has occurred, a melt with a higher silica content results.

pegmatite

A light (felsic) igneous rock that is very coarse-grained.

Pele

Hawaiian goddess of the Volcanoes

Pele's Hair

A naturally spun volcanic glass thats blown away from lava formations, lava falls, or turbulent flows. Generally gold in color

pele's tears

molten lava spews up and as it falls down, it's elongated

peridotite

contain mostly dark colored minerals, chemical composition is ultramafic, rare, in upper mantle

Phanertic

coarse grained

Phenocrysts

large crystals in porphyritic rocks

Plutons

Intrusive igneous rock bodies, including batholiths, stocks, sills, and dikes, formed through mountain-building processes and oceanic-oceanic collisions; can be exposed at Earth's surface due to uplift and erosion.

porphyritic

The texture of igneous rocks that form when slow cooled course-grained rock is erupted. The result is large crystals embedded in smaller crystals.

pumice

Volcanic rock with glassy/vesicular texture that forms when large amounts of gas escape from a melt. Only rocks that floats

Pyroclastic flow

a ground- hugging avalanche of hot ash, pumice, rock fragments, and volcanic gas that rushes down the Mt. 100-400 mph, deadliest aspect of a volcanic eruption and can reach temperatures of 600-800 degrees

rift eruption

a divergent boundary on land

Ring of Fire

A narrow zone that rims the Pacific Ocean and contains most of the active continental volcanoes (composite cones.)

shield volcanoes

Broad, slightly domed volcanoes. They are formed by fluid basaltic lavas and are frown up from the ocean floor to form islands or seamounts. (An example is the Hawaiian chain.)

sill

tabular and concordant plutons form when magma is injected along sedimentary bedding surfaces, horizontal, uniformly thick

skylight

an opening in the roof of a lava tube

stock

smaller batholith that is less than 100m2 above the surface

Strato Volcano

Another name fore Composite volcanoes

tabular

A descriptive word for plutons with a table-top.

tephra

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

texture

appearance of an igneous rock based on the size, shape, and arrangement of crystals

Tree molds

Type of lava formation that is formed when lava surounds a tree, clings against it and drains away

Tsunami

Japanese word for "harbor wave", a volcanic eruptions abruptly displaces ocean water by either an explosion or landslide, Example : Krakatoa

ultramafic

Igneous rocks with mostly dark-colored minerals (specifically peridotite, which is a rare type of rock.)

vent

the surface opening at the top of a pipe

vesicle

voids left by gas bubbles that formed as the lava solidified in fine grained rocks

vesicular

igneous rock texture that has air bubbles, large minerals, and forms with aa

viscosity

a magmas resistance to flow, factors including temp and magmas chemical composition

Volatiles

gaseous components of magma dissolved in the melt. They will readily vaporize at surface pressures

Volcanic Neck

a deposit of hardened magma in a volcano's pipe

Volcano

an opening in the earth's crust through which magma reaches the surface

tuff

A rock fused out of glassy shards when hot ash falls.

xenolith

when a different type of rock is incorporated into another plutonic rock

Amygdaloidal

vesicles completely or partially filled with secondary minerals

pyroclastic texture

a fragmental texture characteristic of igneous rocks composed of pyroclastic materials