The system is fragile: evidences of collapse in extinctions
UNIFORMITARIANISM (_____________, _______________)
The physical processes have occurred through time under the influence
of the ______of _________. The same laws are ________ today.
______________: the present enables understanding of the past.
Problems for Actualism:
A LITTLE HISTORY....
_______________: rocks formed by successive flooding of supernatural
origin.
_________________: (Werner) minerals deposited from a vast sea thar frequently flooded the continents.
Naturalists XVIII & XIX centuries: the Earth is very old and geologic processes have been working for long periods of time: endless time.
Modern Geology:
____________ _____________ (the mind)
____________ _____________ (the communicator)
(and also Arnold (The Terminator) Swartzenegger, gov. CA...
just kidding, erase this last line)
TOOLS
Rock: aggregate of ________________________________
Mineral: naturally occurring inorganic solid element or compound with definite composition and internal crystalline structure.
Three rock groups:
IGNEOUS (plutonic & ______________________)
SEDIMENTARY (fragmental or ________________) and
also biogenic
Fundamental structure: _________________
METAMORPHIC (transformed by _______ and/or ________
from previously existing rocks, without _______________)
Crystalline rocks are __________________________________
Rocks are classified into Rock units for the study of
geologic history. The following list orders them from the least to the
most inclusive unit:
Member
_______________ :
the fundamental rock unit (lithostratigraphic unit)
Group
___________________
GEOLOGIC TIME: CONCEPTS AND PRINCIPLES
Geologic time: deep time
Relative dating _______________________________
Radiometric dating or absolute dating ________________________________
Principles of Relative Dating
UNCONFORMITIES: ________________of erosion or non-deposition
representing a ____________ amount of _______.
A comformable sequence has no depositional break
Types of unconformities
Disconformity: ________________ beds difficult to identify.
Angular unconformity: beds above & below the unconf. form_____________.
Meaning?
Nonconformity: sed. rocks on erosional surface cut on _________________ or ___________ rocks
CORRELATION
Why?: to show ___________________________of rock units in different
areas.
How? surface
lateral continuity, key beds
subsurface core samples
cuttings
geophysical methods
for age correlation use Guide fossils or index fossils
Fossil: remains or ____________ of ancient living organisms
Guide fossil attributes:
__________________
distinct
short ________________
_____________________ studies units of rock according to their geometric relations, composition, origin, age & fossil content.
Time-rock or chronostratigraphic units: unit of
rocks
formed __________________________, however their age (in y.) is not given.
Time units or geochronologic units: the ___________________
in time when the time-rock units were formed.
Biostratigraphic units: units of rocks that have
formed at the same time as indicated by____________________.
(Based on fossil ranges).
Range is the vertical interval through which the fossil
is _____________ in the strata
Zone: basic biostratigrafic unit defined on the
range of a fossil or assemblage of fossils
The Geologic Time Scale is divided in time units
(geochronological units):
http://www.geo.ucalgary.ca/~macrae/timescale/timescale.html
Eons
________
Periods
__________
Age
Corresponding time-rock units (chronostratigraphic units):
Erathem
System
Series
Stage
Mnemonic device for the Geologic time scale:
http://www.pseudonumerology.com/6.htm
ABSOLUTE DATING METHODS
________________: An unstable atomic nucleus is spontaneusly transformed
into an atomic nucleus of a different element.
Methods of decay
• Alpha decay (2p &2n)
• Beta decay (a fast electron from the nucleus)
• Electron capture
Describing the decay rate ___________ isotope
Daughter _________
____________ ____________- Is the time it takes to _________ _________of the parent atoms to decay to the daughter elements.
Age calculation based on __________ _______________
and knowing the half life of the
parent
Uncertainties: Radiometric dating best to determine the ages
of _______________ rocks.
Problems
Cross check: measure two different parent/daughter ratios in the same mineral
Long lived isotopic pairs
Uranium-lead: lunar samples, intrusive rocks, meteorites
Thorium-lead: (separated minerals analyzed)
Potassium-argon: fine grained volcanics (whole rock analyzed)
Other methods • fission track dating ( 40000/
1 mya)
• carbon 14 dating (to date once living material< 70000 y)
• tree-ring dating (time scale extending to 14000 y.a.)
Geologic time scale (units) Eons > Eras > Periods > Epochs
Pieced together by geologists ________________ the use of radiometric
dating
Radiometric ages for the boundaries between the units added later.