Geol 126 midterm 1

rocks rock?

What is science?

discovery, world is understandable through observations

belief knowledge

knowledge unique to each person

research knowledge

universal knowledge, observable and measurable

good science

doubt, recognize biases, several theories may be raised to explain one observation

observation

facts that should be repeatable from one person to the next

interpretation

hypotheses invented to explain observations

pseudoscience

reference to authority rather than observation, use science to promote a message even though its not based on science

plate tectonics theory

outer portion of the earth is broken into plates

What is a rock?

An aggregate of minerals and mineraloids

What is a mineral?

* Naturally occurring
* inorganic solid
* orderly internal structure (crystal lattice)
* definite chemical composition

whole earth composition

* iron 32%
* oxygen 30%
* silicon 15%
* magnesium 14%
* sulfur 3%

most common silicate materials

quarts and feldspar

* example: granite

earth’s core

solid inner iron core

less dense matter began to flow up from the core to make up the surface

deeper into the core, temps rise and pressure increases

accretion (solids form large objects-planets) , differentiation (melting, separates materials, heavier sink-core and lighter rise-crust), contraction (shrinkage from cooling)

crust composition

* Oxygen 47% (O)
* Silicon 28% (Si)
* Aluminum 8% (Al) 
* Iron 5% (Fe)
* Calcium 4% (Cl)
* Sodium 3% (Na)
* Potassium 2.5% (K)
* Magnesium 2% (Mg)

common non-silicate minerals

carbonates, oxides, halides (salts), sulfates, sulfides, minerals composed of one element (gold, copper, sulfur)

coal

mineraloid NOT a mineral, made from plants- organic matter

3 types of rocks

igneous, sedimentary, metamorphic

igneous rocks

* a melted rock that cools and hardens

What is the difference between magma and lava?

* Magma: molten rock beneath the surface
* pluton- glob of magma
* sill- magma travelling horizontally
* dike- magma traveling vertically
* Lava: molten rock erupted onto the surface

two kinds of igneous rocks

* intrusive - cool slowly beneath earth surface
* extrusive, cool quickly on earth surface

sedimentary rocks

* made of disaggregated bits of other rock
* form at the earth’s surface

sedimentary rock process

* weathering attacks preexisting rocks and produces sediment
* sediment transported by either water, wind, or ice and pile up
* deposited- delivered and stops moving
* once in rest needs to be buried to become a rock

clastic sedimentary rocks

made from grains (pieces) that came from weathering

* defined by grain size
* sediment: gravel, sand, silt, clay
* after burial: conglomerate, sandstone, siltstone, shale

chemical sedimentary rocks

made from chemicals that came from weathering of rocks

* chemicals from fluids, and if concentration is high enough, becomes minerals
* ex: carbonates- limestone

metamorphic rocks

heat and pressure cause preexisting rocks to change

* occurs in solid NOT melted state
* protolith (og rock)>> heat and pressure>> metamorphic rock

rock processes

* uplift and weathering
* burial and cementation and compaction
* heat and pressure
* melting
* cooling and crystallization

plate tectonics theory

outer portion of earth is broken into plates

* plates move and interact

3 kinds of plate boundaries

divergent, convergent, transform

divergent boundary

plates pull apart resulting in the formation of new crust from magma

* passive margin (no effects)
* where?
* ocean, rising magma is cooled by water

convergent boundaries

when plates collide, plates smash together

types of convergent boundaries

* Ocean Crust vs. Continental Crust
* Oceanic crust will always subduct because it is more dense(volcanos arise from subducting crust)
* Continental Crust vs. Continental Crust
* They collide resulting in the build up of mountains, produce earthquakes
* Oceanic Crust vs. Oceanic Crust
* older plate will give up and be subducted under the younger plate, formation of volcanic islands

transform boundary

plates slide past each other, earthquake!

plate tectonics evidence: divergent

mid ocean ridges, age of ocean crust

plate tectonics evidence: convergent

earthquakes, volcanoes

general plate tectonics evidence

hot spots and magnetic strips

importance of plate tectonics

control rock cycle

environment

set of conditions that exist today in a particular location

* controls sorting of sediment
* energy of env controls grain size

Sorting of sediment

* Windblown sand: very well sorted
* Beach sand: well sorted
* River sand: moderately sorted
* Glacial sediments: very poorly sorted

terrestrial environment

on land NOT in the ocean

coastal environment

shallow marine environments, lots of fossils come from here

marine environment

deep sea

paleoenvironments

ancient environments

high energy environment

moves large sediment pieces

* gravel>> conglomerate

intermediate energy environment

movement, but not too much, can move sediment

* sand>> sandstone

low energy environment

can’t really move sediment pieces

* fine grained sediment
* silt-clay>> siltstone-shale

sedimentary structures

physical features formed during sediment transport/ deposition

* flat laminations
* ripples
* dunes
* mud cracks
* raindrop impressions

Flat laminations

grains fall out of suspension

* low energy/ quiet water

asymmetric ripples

flow in one direction

* cross strata dip in direction of flow
* sediment will be coarser
* not flat or parallel
* medium energy

symmetric ripples

back and forth flow

* tuning fork
* medium energy

dunes

* asymmetrical
* constrained by depth of flow (air), so can get huge!
* subaerial (windblown)
* high energy

mud cracks

environment dried out!

* no flow and indicates water depth

raindrop impressions

environment dried out but it was also raining

eolian wind environments

* well sorted
* major rock types; sandstone
* frosted grains bc sand is hitting against it

beaches

* well sorted sandstones
* symmetric ripples indicating oscillatory flow

braided river

* major rock types: sandstone and conglomerates
* high energy
* moderately to poorly sorted
* asymmetric cross bedding
* murky water bc fine grain is carried by water

glacial environment

* major rock type: tillite
* poorly sorted
* high energy
* rocks are faceted instead of rounded
* flattened instead of like in water where its rounded

nils stensen

fossils were remains of past organisms by using the shark tooth

* 17th century

kinds of fossils

body, trace and chemical

body fossils

physical remains of an organism

* ex: shells, bones, compressed plants, petrified wood

informs about morphology

* what It could do when it was alive

trace fossils

evidence of activity

* not the organism itself
* ex: footprints, worm trails, coprolites (fossil poop)

informs about what the organism did and how it interacted with the environment

chemical fossils

chemical evidence of past life

* ex: isotopic signatures, organic molecules attributed to life
* only certain chemicals made by life or certain groups
* ex: cholesterol or remains of cholesterol
* informs metabolism

isotope

Element with same number of protons, different number of neutrons

* life tends to prefer lighter isotopes
* concentration of 12C in a rock could indicate the past presence of life, and would represent a chemical fossil

fossilization potential

* bias towards hard parts rather than soft parts
* bias towards low energy
* bias towards ocean rather than land

taphonomy processes

* occurs after the organism dies but before it becomes a fossil
* organism must survive this process to become a fossil

types of taphonomy processes

* Biologic attack
* Ex. Borers, scavengers
* Mechanical attack
* Ex. High energy environments
* Chemical attack
* Ex. Weathering

Steno’s conclusion about geologic time

superposition and original horizontality

superposition

oldest layer at the bottom with successively younger layers above

original horizontality

Sedimentary rocks form horizontal layers \n Thus, inclined sedimentary rocks suffered subsequent disturbance (tectonics!)

crosscutting relationships

Something that cuts across or affects another layer must be younger than the material that’s being affected

stratigraphic columns

Environmental description of each layer

fossil succession

George Cuvier- 1800s

* fossils occur in an order
* some appeared in a layer and then never appeared again
* extinction!

William Smith- 1800s

* rock types change from place to place
* young with young fossil and old with old fossil, always!

index fossils

widespread

short lived

can subdivide geologic time into smaller units

* relative time, no date, just sequence of events

geologic time scale

a record of geologic events and life forms in Earth’s history

* relative

Eon

Phanerozoic

era

in order from youngest to oldest

* Cenozoic (age of mammals)
* Mesozoic (age of dinosaurs)
* Paleozoic (age of tribolites)

Paleozoic periods

in order from youngest to oldest

* Permian
* Carboniferous
* Devonian
* Silurian
* Ordovician
* Cambrian

Mesozoic periods

in order from youngest to oldest

* Cretaceous
* Jurassic
* Triassic

Cenozoic periods

in order from youngest to oldest

* Neogene
* Paleogene

relative time

* The sequence in which events took place
* Chronostratigraphic

absolute time

* the actual time (usually measured in years) as determined by radiometric age dating
* Chronometric

What rocks can be radiometrically dated?

Igneous and Metamorphic

time vs rock

time is continuous but abstract and rock is discontinuous but tangible

meteorites

leftover bits from the formation of solar system

sedimentary record

* sediment accumulation rate varies from place to place
* gives snapshots versus continuous record

taxonomy

* the science of classifying organisms
* looks for differences

phylogeny

 the study of the (evolutionary) relationships between groups of organisms

* looks for similarities

species

* Basic unit of taxonomy and phylogeny 
* Biologic definition
* A population of organism capable of interbreeding and producing fertile offspring
* Genetic definition (better)
* Based on the similarity of DNA in a population 
* % of similarity

morphological species concept

based on similarity of appearance

* morphology = shape
* DNA encodes for shape
* Genes control shape, genes control morphology, so both concepts linked

cladistics

based on parsimony

* simplest is the best
* branching, things don’t directly change, different branches to create more diversity

cladistics vs parsimony

min steps are the best, fewer assumptions

step 1: define characters of taxa

* find characteristic that is either exclusive or common

step 2: construct character matrix

* quantitively assign characteristics to the taxa

step 3: construct tree using parsimony

* how closely taxa are related to each other based on how many characteristics they share

parsimony tree

clade- include the common ancestor and ALL its descendants

paraphyletic

does not include all descedants

poyphyletic

does not contain the most recent common ancestor

DNA

* deoxyribonucleic acid
* the blueprint for life
* polymer of nucleotides

central dogma of biology

DNA>> RNA>> Protein

who discovered dna?

Rosalind Franklin, James Watson and Francis Crick

code of DNA

pairs of 4 nucleotides

* Sequence of dna catalogs the order of adenine, thymine, guanine, cytosine (nucleotides)
* A+t and g+c, only!

Replication of DNA

DNA Polymerase copies DNA very accurately

Transcription of DNA

* RNA Polymerase converts DNA to mRNA
* Genes are transcribed into mRNA

Translation of DNA

* Ribosomes translate mRNA into proteins