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james hutton

who is regarded as the father of geology

charles lyell

who wrote the book Principles of Geology


james huttons concept that geologic operating at preset are the same processes that operated in the past eventually became known as teh principle of ______________ (the present is the key to the past)


a principle that the same processes and natural laws operated in the past are those we can actually observe or infer from observations as operating in the present


dating based on radioactivity allows us to determine a rocks ___________ age (age given in units of time)


numerical age is also known as _________age


_____________ time is the sequence in which events took place , rather than the number of years involved (geologist are more concerned with this number)


the surfaces seperating 2 different rock types or rocks of different ages (used to decipher geological history)


bodies of rock of considerable thickness with recognizable bodies characteristics that make each distiguishable from adjacent rock units (named after geographic features)


the subdiscipline in geography that uses interrelationships between layered rock or sediment to interpret the history of an area

original horizantally

the principle of ____________________ states that beds of sediment deposited in water formed as horizantal or nearly horizantal layers


the principle of _______________ states that within a sequence of undistrubed sedimentary or volcanic rock, the layers get younger going from bottom to top

lateral continuity

the principle of _______________________ states that an original sedimentary layer extends laterally until it taper or thins at its edges

cross cutting relationships

the principle of ___________________________ states that a disrupted pattern is older than the cause of the dispruption

intrusive contact

rock which intruded after orginal rock layer was formed


contacts representing buried erosion surfaces-a surface or contact that represents a gap in the geoligic record with the rock layer above the contact being considerably younger than the rock beneath

tectonic forces

what can cause the overturning or disruption of beds so much that the principle of superposition cannot be used

contact metamorphosed

the tilted layers immediately adjacent to granite bodies are ____________________ a result of intrusion of hot granite magma


the principle of _______________ states that fragments included in a host rock are OLDER than the host rock


in a ________________ the contact representing missing rock strata seperates beds that are parallell to one another (probably the older rock eroded away

angular uncomformity

an __________________ is a contact in which younger strata overlie an erosion surface on tilted or folded layered rock (implies- deposition, lithofication, uplift, erosion)


a _____________ is a contact in which an erosion surface on plutonic or metamorphic rock has been covered by younger sedimenary or volcanic rock (generally indicates deep or long erosion before subsequent burial)


__________________usually means determining time equivalency of rock units (within a region, continent)

physical continuity

this type of correlation traces physically the course a rock unit


correlation by rock type is more reliable if a very ____________sequece of rock or involved

continental drift

what theory uses correlation of rock type as its proof

key bed

a very distinctive layer can be used to correlate rocks over great distances (volcanic ash)


these are common in sedimentary rock and their presence is important for correlation

faunal succession

the discovery of william smith who realized that fossil species succeed one another through the layers in a predictable order


______________ speciallize in the study of fossils


this type of fossil is from a short lived - geographically widespread species

fossil assemblage

several different fossil species in na rock layer (more useful than a single fossil)

standard geologic time scale

a world wide relative time scale - based on fossil assemblage


how many eras are in the geologic time scale


which era in the standard geologic time scale means "old life"

middle life

the mesozoic era means __________________ this was the time of the dinosaurs


which ephoch in time are we in


all the horizantal rock in the grand canyon are ________________

sedimentary deposits

layers of _____________________ can be counted to determine how long lakes existed


the oldest rock found on earth is a ______________ from northwestern canada (dated 4.03 billion years old)

zircon crystal

the oldest mineral is a ____________ from australia which is 4.4 billion years old


if we can determine the ________ of a particular radioactive element and its decay products in a mieral we can calculate how long ago that mineral crystallized

isotopic dating

determinig the age of a rock through its radioactive elements


atoms of a given element that have different numbers of neutrons but the same number of protons

radioactive decay

________________ is the spontanious nuclear change of isotopes with unstable nuclei


what is produced with radioactive decay

geiger counter

what measures the energy in radioactive decay

alpha emission

a radioactive change where the atomic number is reduced by 2 and the atomic mass is reduced by 4 (ex uranium(238) to thorium)

beta emission

a radioactive change which involves the release of an electron from the nucleus (ex. Th (234)to Pa(234))

electron capture

a radioactive change whereby a proton in the nucleus captures an orbitting electron- the proton becomes a neutron
(ex Potassuium becomes Argon)

half life

the rate of proportional decay - the time it takes for a given amount of a radioactive isotope to be reduced by one-half


how many billions of years is potassiums (K)'s half life


how may years is carbon 14's half life


because of the short half life of C14 it is only accurate back to about _______________


what type of rocks are best for dating


what type of rocks are difficult to date reliably


who, in 1866, calculated backwards that the entire earth must have been molton 20-40 million years ago (age found wrong by radioactivity and heat energy)

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