Geology 1121 Ch10 Quiz

What is geologic time?

span of time since earths formation

What are the two ways to classify a rocks age?

relative and numerical

What is relative time?

what happened first, the age of a rock based on the age of other things around it (between 4 MYA and 22 MYA)

What is numerical time?

the physical age of an event/rock (84.4 MYA)

What is the principle of uniformitarianism?

the present is the key to the past

What is geologic history?

series of events organized by relative age

What is the law of inclusion?

any rock fragments that are included in rock must be older than the rock in which they are included

What is the law of fossil succession?

different specie of fossil organisms appear in order in strata, once a fossil species disappears in strata, it never reappears higher in sequence

What is an unconformity?

gap of time in geologic record, separates old rocks from young

What is a disconformity?

a type of unconformity where parallel sedimentary rocks are above and below erosional site

What is stratigraphy?

the study of strata

What are strata?

layers of rock

What is the law of original horizontality?

sediments deposited horizontally/flat by gravity

What is the law of superposition?

strata on top are younger than those on bottom

What is the law of continuity?

sediment spreads are in all directions, layers match up across erosion sites like rivers

What is the law of cross-cutting relations?

any feature that cuts across another in younger

What is the law of baked contacts?

rock around a contact site in baked or heated by the site

What is a nonconformity?

intrusive igneous or metamorphic rock below erosional site which is covered by sedimentary rock

What is angular unconformity?

separates angled layers below erosional surface from horizontal layers above

What is a geologic column?

composite statoscopic chart showing earths entire history

What is the order for geological time subdivisions?

eon, era, period, epoch

What happened in the hadean eon?

inferno earth, creation of the earth and moon

What happened in the archean eon?

beginning of living things, erosion, magnetic field, very little o2 in atmosphere

What happened in the proterozoic eon?

longest eon, protists, fungi, supercontinents, more o2 in atmosphere

What happened in the phanerozoic eon?

visible life, explosion of life, dinosaurs, homosapiens, hominids

What eons does Precambrian include?

hadean, archean, proterozoic

What is an era?

interval of geologic time subdividing the pherozoic eon

What are the 3 eras?

paleozoic, mesozoic, cenozoic

What does the paleozoic era mean?

ancient life

What happened in the mesozoic era?

dinsaurs, middle life

What does the cenozoic era mean?

our era, recent life

What is a period?

interval in geologic time subdividing eras

When do periods start?

cenozoic era

What was the cambrian explosion?

rapid and remarkable diversification of life

What in an epoch?

interval in geologic time subdividing periods of the cenozoic era

What happened in the pliocene epoch?

ice age

How are names for geologic time intervals chosen?

based on rocks, appearance of fossils, and major events like mass extinction

What is geochronology?

science of dating geologic events in years

What are radioactive atoms?

unstable atoms that spontaneously decay in reaching a stable state

What happens while a radioactive atom decays?

energy is released

What is a parent atom?

the atom that decays

What is the daughter atom?

the atom that is produced

What is half life?

time required for ½ the original parent atoms to decay into daughter atoms

Radioactive decay is _______.

exponential

How many half lives can you typically measure?

5

How do we calculate numerical age of geologic material?

measuring the ratio of parent-daughter atoms

What do appropriate radioactive atoms depend on?

sample material (atoms in sample), sample age

C-14 is present in ______ fossils but not _____ fossils

young, old

238U-206Pb can determine the age of what type of material?

oldest

14C-14N can determine the age of what type of material?

young fossils

When does numerical age start in regards to igneous fossils?

when magma or lava cooled

When does numerical age start in regards to metamorphic fossils?

temp at which minerals in the rock became stable

When does numerical age start in regards to sedimentary fossils?

age cannot be determined, you must use cross-cutting relationships

What is the geological time scale?

the intervals of geological time with numerical ages assigned to eons, eras, periods, epochs