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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)
_____________ 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
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
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
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
what can cause the overturning or disruption of beds so much that the principle of superposition cannot be used
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
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)
the discovery of william smith who realized that fossil species succeed one another through the layers in a predictable order
several different fossil species in na rock layer (more useful than a single fossil)
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)
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
atoms of a given element that have different numbers of neutrons but the same number of protons
________________ is the spontanious nuclear change of isotopes with unstable nuclei
a radioactive change where the atomic number is reduced by 2 and the atomic mass is reduced by 4 (ex uranium(238) to thorium)
a radioactive change which involves the release of an electron from the nucleus (ex. Th (234)to Pa(234))
a radioactive change whereby a proton in the nucleus captures an orbitting electron- the proton becomes a neutron
(ex Potassuium becomes Argon)
the rate of proportional decay - the time it takes for a given amount of a radioactive isotope to be reduced by one-half
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