Exam I Flashcards
Difference between hypothesis, theory, and law
Hypothesis: development of an explanation that fits the data
Theory: a hypothesis that has survived repeated tests and is supported by evidence
Law: description of natural phenomenon or principle that holds true
Overview of scientific method
observation, hypothesis, experiment, conclusion, maybe re-design hypothesis and repeat
What is meant by “deep time”
the concept of geologic time that spans billions of years into the past
What is catastrophism, and how does that differ from uniformitarianism and actualism
catastrophism: changes to earth’s surface only happen during violent, sudden events
uniformitarianism: geologic processes are uniform through time
actualism: processes are the same but the rates may differ over time
What are earth’s four systems, and how do they interact with each other?
Hydrosphere
Biosphere
Atmosphere
Lithosphere
What role does the exosphere play?
deals with solar and cosmic radiation, as well as comets, asteroids, and meteoroids
What is convection and how is it involved in earth’s systems?
Convection is the simultaneous movement of heat and mass
Radioactive decay from earth’s core drives mantle convection, creating movement, formation, and destruction of plates
Also convection in atmosphere of warm/cold air
also convection in hydrosphere, thermohaline circulation
Definition of mineral/how do they form?
Defintion: naturally occurring, inorganic, crystalline structure, definable chem composition
form in one of the following ways:
1) cooling of magma
2) recrystallization
3) precipitation from a liquid
Know major mineral groups, examples of each, and their importance
Silicates: silicon and oxygen, common in most rocks, ex: quartz, feldspar, mica, zircon, olivine, clay minerals
Carbonates: soft, form in presence of water, ex: calcite, dolomite, aragonite
evaporites: subjected to intense evaporation, indicates arid climates, ex: halite, gypsum, anhydrite
native elements, sulfides, oxides: metals in particular, plus magnetite (oxide)
Which mineral group is the most common?
Silicates
Which mineral group(s) form in association with water?
Carbonates
List key properties used to identify minerals
Color, streak, density, effervescence, magnetism, taste, fluorescence, hardness, cleavage
How and where do igneous rocks form?
Form from cooling of magma that comes hot deep crust and upper mantle
Compare and contrast granite (con. crust) and basalt (ocean crust) based on intrusive/extrusive origin, cooling rates, mineral size, and composition.
Granite: high silica, high viscosity magma, intrusive origin, slow cooling, large crystals
Basalt: low silica, low viscosity magma, extrusive origin (but eruptions are non explosive), fast cooling, small crystals
Which rock types represent violent, volcanic eruptions?
Rhyolite, andesite
How and where to sedimentary rocks form?
Forms through weathering (physical/chemical), then erosion, then transportation, then deposition and compaction…all on earth’s surface
What factors are important to sedimentary formation?
Weathering, erosion, lithification
What is the difference between clastic and chemical sedimentary rocks?
Clastic: loose sediment that is lithified via burial, compaction, and cementation
Chemical: chemical processes like dissolution, and precipitation break down/build up ions
How and where do metamorphic rocks form?
recrystallization of pre-existing rocks without melting in deep crust/upper mantle
Compare and contrast foliated slate (low grade) and gneiss (high grade) vs non foliated quartzite and marble
slate: small crystals, subtle foliation
gneiss: high temp and pressure, large crystals, foliation
quartzite and marble: no foliation, small, grainy crystals
What are the types of metamorphism?
regional: high pressure and temp over large regions (mountain building, plate collisions)
contact: heat/fluid from lava/magma, low grade
What is the rock cycle?
Transformation of one rock type into another through 1) melting 2) heat and pressure and 3) erosion and cementation
What early theories serve as the basis for plate tectonic theory?
Continental drift + seafloor spreading
What evidence supports continental drift?
fit of the continents fossils rocks mountain ranges climate belts
What is Pangea?
the supercontinent that preceded our modern day continents
Why was Wegener’s hypothesis not initially accepted?
He had no mechanism for HOW the continents drifted, only that they did
What evidence supports sea floor spreading?
mid ocean ridges age of seafloor thickness of sediment paleomagnetism magnetic reversals
What role does convection play in plate tectonics?
Radioactive decay from earth’s core drives mantle convection, creating movement, formation, and destruction of plates
What are ridge-push/slab pull?
Plates pushed away at ocean ridges (hot, less dense)
Plates pulled down in subduction (cold, dense)
What are the three plate boundary types and what features are found with them?
Divergent (mid-ocean ridge, rift, normal faults, passive margins);
convergent, 3 types: ocean-ocean, ocean-continent, continent-continent (subduction zones, volcanic arcs, trenches, Wadati-Benioff Zone, reverse faults, folds, active margins),
transform (strike-slip faults, off-set mid-ocean ridges);
Which boundary creates crust? Destroys it?
creates: divergent
destroys: convergent
What is the average rate at which plates move?
1-15/2-20 cm per year
What is a mantle plume/hotspot?
mantle plume: stationary heat source in mantle
hot spot: fixed heat source that generates a trail of volcanoes as plates move over it
What are asthenosphere and lithosphere? What roles do they play in tectonic theory?
Tectonic plates formed w/in lithosphere, interacting and moving over plastic asthenosphere
What are all those fun principles used for relative age dating?
Superposition, Lateral Continuity, Original Horizontality, Inclusions, Cross-cutting Relations, and Faunal Succession
What is an unconformity? What are the three types of unconformities and how do you identify them?
definition: erosional gaps in the geologic record, formed by uplift and erosion
angular unconformity, disconformity, nonconformity
How are fossils used to date rocks?
fossils have a geologic range, spanning from their first appearance in a specific strata to their last appearance
What is the range zone vs concurrent range zone of fossils?
range zone: rock body that represents the total life span of a specific fossil
concurrent rang zone: overlapping ranges of 2 or species
What makes a good index fossil?
abundant, widely dispersed, easy to identify
What are some problems in using fossils for correlation
sudden disappearance may mean extinction or they moved out
first appearance may mean they evolved there or moved in
reworked fossils could have been eroded and transported from elsewhere
What are the different methods used to calculate the age of the earth?
Biblical, Evolution (6,000 years old), Deposition Rates (million-billion), Ocean Salinity (100 million), Cooling Rate (20-40 million), Radioactive decay (becquerel and curie)
What is the age of the earth according to geologic theory?
4.56 billion years old
How we can use radioactive decay to determine a numerical age
through parent isotopes, daughter isotopes, and half lives
What is an isotope?
varieties of the same element with equal atomic numbers but different mass numbers (varying neutrons)
What are parent atoms, daughter atoms, half lives?
parent: what you start with
daughter: product of decay of parent
half life: the time it takes for half of the parent atoms to decay into daughter atoms
Why must minerals behave as such a closed system?
so that it cannot exchange isotopes with the environment any longer to provide an accurate age
How does carbon-14 dating work and what does it date?
Carbon-14 created by cosmic radiation bombarding N-14 atoms, consumed by plants/animals, then trapped and decays back into N-14
dates organic material containing carbon in sediments
Know how to calculate an age given the proportion of parent to daughter atoms and the half-life of an isotope
hell yeah brother,
100-50-25-12.5
How was the geologic time scale formed and what is it based on?
Formed by several scientists, primarily Arthur Homes in 1913 (uranium dating), based on changes on fossils which mark boundaries
Know the hierarchy of geologic time units: Eons, Eras, Periods, and Epochs. Which represent longer/shorter periods of time?
you should know this bitch
