Geology 201 Lab Midterm

what are the 3 kinds of north displayed on a map?

true north, magnetic north, and grid north

National Topographic System (NTS)

Canada's official map index system
divides into large, numbered blocks based on lat+long
designed to locate areas, not points

Universal Transverse Mercator (UTM)

designed to locate points, not areas
numeric code only, no number/letter combos
uses a decimal system rather than degrees-minutes-seconds
2cm = 1km
ex. zone 11 699 100 easting 5657 250 northing

Latitude and Longitude

divide earth with lines
W-E = longitude
N-S = latitude
ex. 114°9'40" W 51°1'40" N

colour

least reliable physical property.
felsic = light
mafic = dark

lustre

quality of light reflected from a mineral: metallic, vitreous, earthy

hardness

measure of how easily a mineral can be scratched

streak

refers to the colour of a powdered mineral

cleavage

a mineral's ability to split easily along flat points of weakness.

habit

the shape of an unbroken mineral crystal; shape it naturally forms

homogenous

made up of a single material

heterogenous

made up of several materials

biogenic

consisting of the remains of organisms or formed due to the activity of organisms

abiogenic

resulting from non-biological chemical reactions

aggregate of crystals

rock composed of many crystals

aggregate of grains

rock composed of fragments of: rocks, crystals, or fossils that show signs of physical reworking from current transport or erosion

amorphous

does not contain crystals or grains, typically glassy

mineral

a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition

fossil

any evidence of life in the rock record. includes plant and animal remains as well as traces of biological activities (footprints)

rock

aggregate of mineral crystals, fossils, grains, or a mass of natural glass

Igneous rocks form by

the crystallization of molten magma or lava (intergrown crystals)

intrusive igneous rock

rock that forms below Earth's surface (longer to cool, typically larger crystals)

extrusive igneous rock

rock that forms from the cooling and crystallization above the Earth's surface
(less time to cool, typically smaller crystals)

phaneritic texture

coarse-grained, crystals are large enough to be seen by naked eye, formed by slow cooling (intrusive)

aphanitic texture

fine grained, crystals cannot be seen with the naked eye, formed by fast cooling (extrusive)

glassy/amorphous texture

A texture formed when a rock cools so fast it doesn't have time to crystallize

porphyritic texture

an igneous texture consisting of large crystals embedded in a matrix of much smaller crystals

phenocrysts

large crystals in porphyritic rocks
(igneous)

vesicular texture

describes a rock containing vesicles caused by gas being trapped during crystallization

mafic rocks (igneous)

dark-colored rocks that are silica poor and iron and magnesium rich. examples:
olivine, pyroxene, plagioclase, and amphibole

intermediate rocks (igneous)

examples: plagioclase, hornblende, quartz, pyroxene, biotite, k-feldspar

felsic rocks (igneous)

light colored rocks that are silica rich and iron and magnesium poor. examples: plagioclase, k-feldspar, quartz, amphibole, and biotite

sedimentary rocks form by:

sediments by compaction and cementation, evaporation of water & organic remains

crystalline texture (non-clastic, sedimentary)

- a term for the texture of sedimentary rocks in which the minerals form a pattern of interlocking crystals
- consist of inter-grown crystals (may resemble igneous rocks)

clastic texture (sedimentary)

- a term for the texture of sedimentary rocks in which an aggregate of grains have been subsequently cemented together

chemical vs clastic sedimentary rocks

clastic: deposition and subsequent cementation and compaction of sediment
chemical: precipitation of minerals out of a solution (ex. limestone and rock salt)

framework

consists of packed clasts that are partial or in full contact with one another (majority of rock)

matrix

consists of smaller grains that fill spaces between the larger framework grains

cement

bind the framework and matrix to form sedimentary rocks

pore space

non-solid space between grains that is filled with fluid or gas

conglomerate

a sedimentary rock made from small rounded stones that have been cemented together

breccia

coarse sedimentary rock consisting of angular fragments; or rock broken into angular fragments by faulting

sorting

refers to the uniformity of grain size; well sorted sediments will have grains of approximately equal size

planar bedding

horizontal sedimentary beds that are roughly parallel to each other

ripple marks

Small waves of sediment formed by running water or blowing wind

asymmetrical ripples

indicate water or wind flowing in one direction (think river)

symmetrical ripples

indicate water or wind flowing in an oscillatory pattern
(think tide/waves)

cross bedding

refers to large scale equivalent of ripple cross lamina (dip towards dominant current direction)

graded bedding

type of bedding in which particle sizes become progressively heavier and coarser toward the bottom layers

a rock is considered dolomitic when:

it reacts WEAKLY with HCl

Metamorphic rocks form from

igneous and sedimentary rocks that undergo a significant change in pressure or temperature. *NO MELTING OCCURS*

regional metamorphism

formation of metamorphic rock bodies that are hundreds of square kilometers in size
*convergent boundaries/mountain ranges

contact metamorphism

formation of a metamorphic rock caused by magma coming into contact with existing rock

foliation

an arrangement of minerals in flat or wavy parallel bands.

metamorphic index minerals (lowest to highest)

chlorite (green)
biotite/muscovite
garnet (red)
kyanite (blue)

porphyroblast

large crystals that form in solid rock by the reorganization of atoms during metamorphism

protolith

the original rock from which a metamorphic rock formed

slate

a metamorphic rock with clean, flat breakage along closely spaced planes due to parallel arrangement of microscopic crystals of clay and mica (slaty texture). Slates are shinier than shales, generally having an egg-shell sheen

phyllite

a metamorphic rock with very closely spaced parallel planes and glossy appearance due to the parallel alignment of microscopic mica crystals (phyllitic texture).Phyllite is shinier than slate because the reflective mica crystals are larger, giving the rock a satin sheen

schist

a metamorphic rock with approximately parallel arrangement of mica crystals large enough to see with the naked eye (schistose texture). To fully name a schist, you must include one to two of its most common index minerals.

gneiss

a metamorphic rock with discrete layers of different mineral content giving the rock a banded appearance (gneissic texture). Typically, the dark bands are composed of hornblende and/or biotite, whereas the light bands are composed of quartz and feldspars

the protolith mudstone/shale can become what after metamorphosis?

slate
phyllite
schist

the protolith mudstone/felsic igneous rock can become what after metamorphosis?

gneiss

the protolith quartz sandstone can become what after metamorphosis?

quartzite

the protoliths limestone or dolostone (carbonate rocks) can become what after metamorphosis?

marble

if the protolith is a conglomerate what can this become after metamorphosis

metaconglomerate

if the protolith is a mafic igneous rock like basalt or gabbro what can this become after metamorphosis

amphibolite

3 methods of direct preservation that produce unaltered remains

unaltered, desiccation, embedding

unaltered preservation

hard parts remain unchanged (shells, bones, teeth)

desiccation

freezing or mummification under dry (desert) or acidic (bog) conditions

embedding

in wax and amber (desiccation also occurs in this mold)

5 methods of direct preservation that produce altered remains

recrystallization, replacement, permineralization, petrification, and carbonization

recrystallization

minerals change to a more stable form without changing chemical composition. often involves an increase in crystal size and makes shells more dull

replacement

minerals making up a fossil are completely replaced by a new mineral with a different composition

permineralization

pores, or empty body chambers are filled with a mineral

petrifaction

organic tissue of fossil is replaced by a new mineral. note: pores within the tissue are permineralized

carbonization

volatiles like water are removed (often via heat and compaction) leaving a thin, carbon film

what are the 2 methods of indirect preservation?

molds and casts

molds

impressions of remains
external: organism stamped into sediment
internal: interior of organism is filled with sediment and shell dissolves away, leaving behind an internal mold
note: mold is a negative (inverse of original shape)

casts

exact replicas of remains
if an external mold is filled with sediment/minerals, a cast is created.
note: cast is a positive (same as original shape)

principle of original horizontality

sediments are originally deposited on horizontal or nearly-horizontal surfaces

principle of superposition

rocks that are highest in an undeformed sedimentary structure are the youngest and rocks that are lowest are oldest

principle of cross cutting relationships

the rock that cuts across a structure is younger than the structure it cuts through

unconsolidated sediments

recent deposits that have not yet been cemented or compacted enough to make up rocks, forming sand and gravel deposits rather than sandstone or conglomerate units

alluvium

unconsolidated clastic (or detrital) material deposited by a stream or other body of running water

bedrock

solid rock that underlies soils or other unconsolidated, superficial material

drumlin

hills of sediment (generally a quarter of a mile or more in length) that have been streamlined by glacier flow

esker

ridges made of sands and gravels deposited by glacial meltwater flowing through tunnels within and underneath glaciers, or through meltwater channels on top of glaciers

braided stream

multi-threaded channels that branch and merge to create the characteristic braided pattern

meandering stream

single-channel that winds through a valley

oxbow lakes

a U-shaped lake or pool that forms when a wide meander of a river is cut off, creating a free-standing body of water

shell with 2 valves that are not identical, but each valve is bilaterally symmetrical on itself. often ribbed valve surfaces with wing-like extensions on either side

brachiopod

altered: permineralization
*hint this is a bone

dinosaur bone fragment

internal mold
shell commonly with 2 identical valves (mirror images) joined by a hinge. has a raised protuberance called an umbo arises near the hinge

bivalve

external mold
segmented organism divided into 3 parts; head (cephalon), body (thorax), and tail (pygidium)
this particular fossil only shows the head of this organism

trilobite cephalon

this sticky substance that hardens to a crystal-like form is capable of producing unaltered remains through embedding

amber

altered: recrystallization
this is an organism that was recrystallized in dolostone

coral in dolostone

unaltered remains
shell commonly with 2 identical valves (mirror images) joined by a hinge. has a raised protuberance called an umbo arises near the hinge
*hint, not a brachiopod

bivalve shell

altered: petrification
*hint, not an animal

wood

altered: dessication
*hint, not an animal

walnut