earth 121

Regional metamorphism of slate

Regional metamorphism of slate

slate (fine, slaty, dull), phyllite (fine, slaty, silky), schist (coarse, schistose), gneiss (coarse, gneissic banding)

Non-Foliated Metamorphic Rocks

Quartzite - quartz Marble - calcite

Coarse grained sedimentary

conglomerate (round, >2mm, quartz and chert), breccia (angular, any clasts) (rivers and alluvial fans)

arenaceous sedimentary

sandstone (quartz), arkose (quartz and feldspar), greywacke (poorly sorted). (rivers, beaches, dunes)

fine grained sedimentary

siltstone (non-fissile, quartz and clay, flood plain deposits)

argillaceous sedimentary

shale (fissile, clay and quartz, flood plain deposits)

depositional environment

evaporite, hot dry. carbonate, shallow sea. feldspar, continental. red, desert. black, plant, swamp.

cryptocrystalline (chalcedony)

chert (light), flint (dark), jasper (red), precipitate from groundwater

Limestone

crystalline, fine, calcite, warm shallow seas

dolostone

medium, crystalline, dolomite

evaporites

gypsum, salt

coal

bioclastic, noncrystalline, black

igneous

plutonic: granite, syenite, diorite, gabbro volcanic: rhyolite, andesite, basalt pumice obsidian

light igneous

felsic, K feldspar, biotite, muscovite

dark igneous

mafic, plagioclase, olivine, pyroxene

Gypsum

2, white/translucent, white

Calcite

3, colourless, white

orthoclase

6, light grey, white

quartz

7, colourless, none

plagioclase

6, grey, none

hornblende

6, black, black, glassy

muscovite

3, colourless, white, sheets

serpentine mineral

spooky

epidote

6, green, none

garnet

7.5, green, none, conchoidal

chalcedony

6, brown, none, banded, conchoidal

biotite

3, black, brown, sheets

dolomite

4, red, white, 2 direction

kaolinite

1, white, white

hematite

5, red, red

augite

5, black, grey, 2 direction

pyrite

6, yellow, black, metallic

magnetite

5, black, black, metallic, uneven fracture

graphite

1, black, grey, metallic

cleavage

mineral’s tendency to break along flat, parallel surfaces. Each set is a different direction.

hardness

measure of mineral’s resistance to scratching. quartz=7, plate=5.5, fingernail=2

specific gravity

ratio of density of sample to water

crystallography terms

prismatic-rectangular parallel faces, pyramidal-symmetrical and triangular, rhombic-cube/rectangle

massive-no crystal form, foliated-thin sheets

cleavage quality

perfect-smooth-mirror like surface and hard to break in other direction

good-small steps between surfaces and can be broken in other directions

poor-steps numerous and many small planes

fracture types

conchoidal-breaking with smooth curve. fibrous (asbestos), uneven, earthy

reaction with acid

carbonates effervesce CO2 when HCl is added. Calcite reacts vigorously, dolomite softly.

striations

common on crystals and plagioclase

ore-minerals

minerals from which metals are extracted (gypsum, halite, fluorite)

industrial minerals

calcite, dolomite, feldspar, mica, talc, etc.

continental drift evidence

fit of shorelines, striations, fossil record, submarine mountain chains

submarine mountain chains

aka mid ocean ridges, diversional boundaries, spreading centres, new basaltic magma is extruded, newest rock at centre

subduction zones

parallel coast trenches where lithosphere is consumed under continent because it is denser, causes earthquakes, folding, and faulting into mountains

transform faults

mid ocean, shearing motion, focus earthquakes

paleomagnetism

iron-bearing materials in magma are magnetized in the direction of earth’s magnetic field, stripes of normal and reverse centre around ridges

epicentre

place where quake originates is focus, spot directly above is epicentre

seismic waves

primary (longitudinal) are fast and first, secondary (transverse) are slower, greater time between mean epicentre is further

map rules

drawn to scale, top is N, boundaries are latitude (E-W, 0-90) and longitude (N-S. 0-180)

topographic contour rules

mean sea level is 0, all lines close somewhere, steeper lines are closer together, contours never cross or split, B.M. means benchmark, lines bend upstream, depression marked by ticks

making topographic profiles

use strip of paper and mark contours, set vertical scale, fill in elevation at lines, connect these points with curved lines

verbal scale

written out in a sentence relation two measurements

representative fraction scale

1:x where 1 and x are in the same units

graphic scale

little doodle where one line=x larger units

vertical exaggeration

vertical scale in cross-section larger than horizontal for clarity, =vscale/hscale (in same units) and should always be >1

azimuth

angle measured clockwise from N

quadrant bearing

angle measured from N or S to E or W

other position location techniques

by two directions, triangulation, along streams

Universal Transverse Mercator Grid

earth in 60 (1-60) vertical slices and 20 (C-X but not I and O) horizontal bands. Grid zone found in margins. 100km squares with 1st letter representing row and 2nd column. small numbers are distance in 100km eastward from from western zone boundary. Grid zone 17T, 421400 4682800

geologic map

shows distibution of rock units as they occur at bedrock surface

formation

sequence of rock sufficiently homogenous to be considered one unit, separated from others by contact lines

outcrop

refers to a point on ground where bedrock is exposed

block diagram

combines geologic map and cross-section in a three dimensional drawing

structure

arrangement of rocks below surface, either flat or folded

attitude

position of bed relative to horizontal, dip is max angle madr in direction of greatest inclination. strike is line where bed is at same elevation, line is intersection with inclined plane. strike and dip always at right angles

clinometer

used to measure angle of dip

stereoscopic air photos

two overlapping photos that when viewed under a stereoscopic lens give a 3d effect

position by land survey

legal subdivision (16 units in section), section (36 1-mile^2 units), township #X, Range #X

folded strata

show considerable changes in dip due to crustal movement.

single-axis (simple) folds

bent about one direction with two limbs and on nose/hinge

fold axis

orientation of folds, can be divided in half by axial plane along fold axis. described by strike and dip of axial plane and angle of plunge of axis

anticline

convex upwards fold with older strata in centre and younger towards limbs

syncline

upwards concave folds with youngest in centre and older towards limbs

plunging folds

fold axis is not horizontal resulting in angle of plunge between fold axis and horizontal

dome

relative high point with closed layers, oldest rock layer in centre

fault

fractures of crust along which relative displacement of the rock masses on either side occur (unless joint)

slip types

net: total displacement

strike: parallel to strike

dip: parallel to dip

throw: vertical

heave: horizontal

normal fault

hanging wall moves down and footwall up

strike-slip

parallel to strike aka tear/wrench, left-handed vs. right depending on which side moves towards observer

diagonal-slip

moves both horizontally and vertically

law of original horizontality

if we observe rock layers inclined to the horizontal there must have been a period of disturbance that tilted the beds

principle of superposition

sedimentary layers will form in order of decreasing age. if the order is disrupted we look for ripple marks, graded bedding, cross bedding, etc.

principle of inclusions

rock unit with inclusions must be younger than inclusions

principle of cross-cutting relationships

igneous intrusions are younger than the bodies they intrude into

discordant intrusions

dyke, batholith (>100km2), stock (100km2<)

concordant intrusions

sill (strip following strike), laccolith (parallel circular), lopolith (parallel elliptical)

disconformity

strata below unconformity are parallel to those above

angular nonconformity

strata below unconformity are at an angle to those above

nonconformity

sedimentary strata form on top of older igneous rock

quaternary

age of humans, humans 300000ya, ice ages and interglacial

paleo and neogene

age of the mammal. eo, neo, oligi, mio, pliocene. angiosperms and grasslands. mammals and birds develop. columbia river and laramide orogeny.

cretaceous

age of the dinosaur. reptiles have big developments. australia and antartica separate. ammonites, bivalves and gastropods.

triassic

age of the ammonite. india, laurasia, and gondwana separate. dinosaurs and mammals appear. gymnosperms.

ornithischian dinos

ankylosaur, ceratopsian, ornithopod, pachycephalosaur, stegosaur

saurischian dinos

theropod and sauropod

permian

Pangaea forms, super mass extinction, reptiles are doing well

carboniferous

age of amphibians and coal forests. gondwana glaciation and alleghenian orogeny. insects and sharks! first reptiles. crionoids, brachiopods, and corals. ferns, scale trees, and rushes