geology chapter 4

felsic

freezing of the magma that remains after much fractional crystallization has occurred, _______ igneous rock

Vesicles

gas bubbles open holes where glassy rocks form

magma

molten rock (melt) beneath the earth's surface

lava

molten rock (melt) that has emerged onto earths surface

in a NON orderly pattern, they are in clusters or chains

molten rock molecules lie _______

mantle plum and mid ocean ridges

where does decompression melting happen

1. hot spots 2. midocean ridges/ rifts

where does decompression melting take place

subduction zone

where does flux melting occur

laccoth

A blister-shaped igneous intrusion that forms when magma injects between layers underground in a manner that pushes overlying layers upward to form a dome.

volcanic arc

A curving chain of active volcanoes formed adjacent to a convergent plate boundary.

sills

A nearly horizontal tabletop-shaped tabular intrusion that occurs between the layers of country rock.

stoping

A process by which magma intrudes; blocks of wall rock break off and then sink into the magma.

large igenous province

A region in which huge volumes of lava and/or ash erupted over a relatively short interval of geologic time.

fragmental igneous rocks

A rock consisting of igneous chunks and/or shards that are packed together, welded together, or cemented together after having solidified.

magma chamber

A space below ground filled with magma.

dike

A tabular (wall-shaped) intrusion of rock that cuts across the layering of country rock.

crystalline igenous rocks

An igneous rock that consists of minerals that grew when a melt solidified, and eventually interlock like pieces of a jigsaw puzzle.

pluton

An irregular or blob-shaped intrusion; can range in size from tens of m across to tens of km across.

pyroclastic debris

Fragmented material that sprayed out of a volcano and landed on the ground or sea floor in solid form.

glassy

If a melt cools very rapidly, it can become solid before seeds have grown into crystals, it forms a _______ rock

mafic

If an originally mafic magma freezes before much fractional crystallization has occurred a ______ igneous rock forms

Glassy igenous rocks

Igneous rock consisting entirely of glass, or of tiny crystals surrounded by a glass matrix.

igneous rock

Rock that forms when hot molten rock (magma or lava) cools and freezes solid.

source-rock composition

The composition of a melt reflects the composition of the solid from which it was derived.

fractional crystallization

The process by which a magma becomes progressively more silicic as it cools, because early-formed crystals settle out.

viscosity

The resistance of material to flow.

volcanic ash

Tiny glass shards formed when a fine spray of exploded lava freezes instantly upon contact with the atmosphere.

Obsidian

Volcanic glass used in tools, mirrors, and knives

aphanetic

a melt that cools rapidly, but not glass rapidly

large crystals

a melt that cools slowly

xenolith

a stoped rock that does not fully melt and becomes surrounded by new igneous rock

lava flow

a syrupy red-yellow stream

Silica (SiO2)

all molten rocks contain

rocks with crystals too small to see with the naked eye

aphaneritic

aphanetic

crystals so small you cant see them

phaneretic

crystals you can see with your eyes

very hot magma rises from the mantle to the crust

describe heat transfer melting

Lava is above Earth's surface and magma is below Earth's surface

difference between magma and lava

volatile

evaporates easily, H20 CO2

- hot mantle rock rises slowly -pressure decreases -temperature remains unchanged

explain decompression melting

-volatiles mix with hot mantle rock -that breaks the chemical bond

explain flux melting

volcanic

extrusive rocks are aka

pumice

felsic rock with a ton of tiny vesicles that can float like strofoam

a vent from which melt that originates inside the earth emerges into the planet's surface

first part of volcano definition

Porphyritic

have larger crystals (called phenocrysts) surrounded by a mass of fine crystals (called groundmass).

they form in dikes, BUT they are not cooled slowly and still have large crystals

how are pegmatites the exception to the cooling-texture rate

silica composition

how do geologists classify magma

freezing of magma underground after it has intruded into wall rock

how does an igenous rock form

by the solidifying (freezing) of a melt

how does an igneous rock form

650-1,100ºC

igneous rocks freezing point

oceanic crust

igneous rocks make up the entire __________ _______

melt

incandescent molten rock

plutonic

intrusive rocks are aka

phenocrysts

larger crystals are called

Fine-grained (aphanitic)

lava flows, dikes, and sills are made up of ________ textured rock

intermediate

melt that composition is partway between that of mafic and felsic melts.

mafic

melts that contain a relatively high proportion of magnesium oxide and iron oxide compared to silica

felsic

melts that have a fairly high proportion of silica, compared to magnesium oxide and iron oxide

ultramafic

melts that have an even higher proportion of magnesium oxide and iron oxide, relative to silica

mafic magma

partial melting of an ultramafic rock results in _______

rocks with crystals large enough to see with the naked eye

phaneritic

Coarse grained

plutons tend to be made of ________ textured rock

pyroclastic rock

rock made from fragments that were blown out of a volcano during an explosion and were then packed or welded together

intrusive

rocks with larger crystals are intrusive or extrusive

extrusive

rocks with smaller crystals are intrusive or extrusive

a hill or mountain built from the products of an eruption

second part of volcano definition

lava flow

the area covered by lava as it pours out of a volcano's vent

solid

the crust and mantle are _______

pegmatities

the exception to the cooling-texture rate

partial melting

the process by which different minerals in rock melt at different temperatures

Assimilation

the process of magma contamination in which blocks of wall rock fall into the magma chamber and dissolve

Bowen's Reaction Series

the sequence in which different silicate minerals crystallize during the progressive cooling of a melt

upward

the temperature of the earth decreases as you go ______

ultramafic

type of igenous rock with less than 45% Sio2

mafic

type of igneous rock with 45-50% SiO2

intermediate

type of igneous rock with 50-65% SIO2

felsic

type of igneous rock with 65-75% SiO2

15%

wet melts include _____ volitiles

flux melting

what causes volcanism at convergent boundaries

the plume itself does not consist of magma, it is composed of solid rock that is hot enough to be relatively soft so that it can flow

what does the plume hypothesis say

obsidian

what example of glassy rock is used

continental volcanic arc

what happens when oceanic lithosphere subducts beneath continental lithosphere

volcanic island arc

what happens when one oceanic crust subducts underneath another

explosive

what kind of magma is felsic magma

interlocking crystals

what texture does a crystalline rock have

no crystalline structure

what texture does a glassy rock have

fragmental

what texture does a pyroclastic rock have

pyroclastic, volcanic ash

what type of rock is tuff and what is it made of

the freezing of lava above ground, in contact with air/water, after it extrudes/erupts

when does extrusive rock form

they form from water rich melts so atoms can diffuse rapidly

why do pegmatites form differently