Geo test

extrusive

(volcanic) rocks formed by freezing of lava above the ground

intrusive

(plutonic) rocks formed by the freezing of lava below the ground

plutons

massive bodies of intrusive igneous rock formed when magma cools and solidifies beneath the Earth’s surface

dikes

cut across rock layers and can occur in swarms

sills

parallel rock layers

igneous textures

crystalline, fragmental, glassy

fragmental

clasts cemented or welded together (pyroclastics)

phaneritic

course grained crystals

aphaneitic

fine grained crystals

porphyritic

large crystals surrounded by fine mass

pumice

a felsic glassy rock with tiny vesicles

scoria

a mafic rock with many vesicles

felsic

high silicia, K-feldspar and quartz

intermediate

even mixtures of felsic minerals and mafic minterals

mafic

less silicia, dominated by plagioclase pyroxene

batholith

a group of plutons that covers a large area

melting due to compression

a decrease in pressure while temperature remains constant, creates a melt

mid-oceanic ridge

a continuous, underwater mountain range formed by plate tectonics at divergent plate boundaries, where Earth's tectonic plates pull apart

continental rift

the slow, large-scale movement of Earth's continents relative to each other and ocean basins over geologic time

hot spots

an area of volcanic activity fed by unusually hot mantle material rising from deep within the Earth, independent of tectonic plate boundaries

flux melting

mixing of volatiles, eg. H2O, CO2, from the ocean with hot, dry rock helps break chemical bonds and creating a melt

heat transfer

rising hot magma into the crust, the heat raises the temperature of the adjacant rocks

Low viscosity

hotter, less SIO2, mafic, more volatiles- water

high viscosity

cooler, more SIO2, felsic, less volatiles

fractional crystallization

a process where different minerals grow in sequence so the melt composition chnages progressively, as cooling takes place

Bowen’s reaction series

first to crystallize is the last to mlt. And vice versa

sediment

consists of loose fragments of rocks or minerals broken off bedrock, shells or shell fragments, and/or mineral crystals that precipitate directly out of the water

weathering

a process that corrodes or breaks up a rock and turns it into loose debris

physical weathering

involves the mechanical breakdown of rocks into unconnected grains or chunks known as clasts

frost wedging

water expands abour 9% frozen exerting a force on the surrounding rocks

root wedging

as roots grow apply pressure and breaks rock

salt wedging

occurs in arid climates, where salts dissolved in water precipitate and exert forces on the surrounding rock

thermal expansion and contraction

intense heat expands the outer layers of rock, and on cooling, the layer contract

animal attack

burrowing creatures, gophers, including humans

chemical weathering

refers to process of disintegration of rocks/minerals by chemical reactions. water, oxygen, acid

dissolution

water dissolves minerals, affecting primarily salts and carbonates

hydrolysis

the chemical reaction between the hydrogen ions and hydroxl ions of water and a mineral’s ions

oxidation

reaction with oxygen, usually occurs in iron-bearing rocks/minerals, producing rust

differential weathering

occurs faster at edges and corners of a block than on a flat face

types of sedimentary rocks

clastic, biochemical, organic, chemical

clastic

consists of mineral grains, rock fragments, and cementing material

lithification

process of converting sediments into solid rock

angularity

the degree of edge or corner smoothness

sphericity

the degree to which the shape of a clast approaches that of a sphere

breccia

coarse, angular rock fragments

conglomerate

rounded rock clasts

metamorphism

the change of minerals or texture (distinct arrangement of minerals) in pre-existing rocks, without the rock melting into liquid magma

metamorphic rock

formed from pre-existing rocks undergo a solid state change in response to a chnage in environment

recrystallization

shape and size of grain change, no chnage in identity

neocrystallization

growth of the new minerals that differ from those of the protolith, under pressure, elements regroup and form new minerals

plastic deformation

mineral grains soften and change shape when rock is squeezed or sheared at elevated temperatureand presure

differential stress

causess minerals to develop a ductile fabric with a preferred orientation

compression

squeezing that flattens the objects

tension

stretching that elongates the objects

shear stress

movement parallel to a surface moves one part sideways relative to another

hydrothermal fluid

accelerates metamorphic reactions

foliated texture

is the parallel planar surface/layer common to many metamorphic rocks

non-foliated rocks

have no planar fabric evident because they lack inequant minerals and/or they recrystallized without differential stress

slate

fine-grained, low-grade metamorphic shale, wih slaty cleavage

phyllite

a fine-grained, mica-rich rock, that forms by the metamorphic alteration of slate due to a temperature change high enough to form neocrystallization

schist

a fine to coarsely crystalline rock with larger micas. Has distinct foliation from large micas

gneiss

has distinct compostional bands, comprised of light bands of felsic minerals alternating bands of mafic minerals

Theory of continetal drift

supercontinent (Pangea) fragmented and move apart slowly

bathymetry

the depth variation in the seafloor’s surface

continental lithosphere

felsic and has low density

oceanic lithosphere

mafic/ultramafic and very high density

plate tectonics

the theory that plates move relative to each other at plate boundaries

convergent

plates move toward each other

divergent

plates move away from each other

transform

plates move past each other

active margins

transitions from continental to ocean crust that are plate boundaries

passive margins

transitions from continental to oceanic crust that are not plate tectonics

Wadati-Benioff Zone

a seismic signature that defines the postion of the downgoing tectonic plate down to about 600km

transform faults

plates slides sideways past another, no new formation or consumption

The Rock Cycle

a numerous of ways: igneous, sedimentary, metamorphic, igneous