Geology 12 Chapter 4 review
Four changes that occurred at the beginning of Phanerozoic
1. number of species with shells dramatically increased. 2. individual organism preserved as fossil increased 3. species preserved as fossils increased 4. average size of individual organisms increased.
Two ways to measure Geologic and how there different
Abosolute Time which means the order which the event occurres and the amount of time that passed since they occurred. And Relative Time which means order which the event s occurred and inorder for an event to affect a rock, the rock must first exist.
Cenozoic
Age of Mammals
Mesozoic
Age of Reptiles
Paleozoic
Age of fish and amphibians
Major events that occurred during Arhcean
Earth crust forms
What geological events are recorded by a Disconformity. What can we inferred about the timing of this type of event
Layers above below are a disconformity are parellel (under water deposition) created by uplift & erosion followed by deposition.
Major events that occurred during Proterozioc
Life begins in the sea.
three Hypotheses that explain mass extinction
Meteorite impact Volcanic eruptions Atmospheric-Ocean-Continent system interactions
two different types of correclation of rock units
Methods by which the age relationship between various strata of earths crust are established. determined in two ways one by physical correlation and two fossil correlation.
explain the principle of cross-cutting relationships and how it can be used to determine age relationships among sedimentary rocks
Rocks must first exist before anything can happen to it and for example, a basalt dyke cutting across layers of sandstone.
events recorded by NonConformity
Sedimentary rock overlies igneous rock, so time gap could be around 1 million years.
What geologic event is actually measured by radiometric age determination of an igneous rock or mineral
The time that passed since granite cooled below 350C during uplift and ersosion.
what geoligical evetns are recorded by angulare unconformity. What can be inferred about the timing of this type of event
an Unconformity is a buried erosional or non-depositional surface separating two rocks masses of different ages, indicating that sedment deposition was not continuous. In general the older layer was exposed to erosion for an interval of time before deposition of the younger.
stable isotope
atoms of the same element with different number fo neutons
Major events that occurred during Hadean
earth forms
radioactivity
elements decay at a constant rate and have a built in calendar.
Principle of faunal succession
fossil organisms succeeded one another through time in a definite recognizable order. therefore ages of sedimentary rocks can be recognized from their fossils, plus index fossils can be used to date units of rock.
what to look for when panning for Gold
look for heavy mafic minerals. which is typically dark colored and oftern with to red tinges.
Unstable isotope
over time the nuclei spontaneously decays.
parent and daughter isotopes
parent isotopes decay while daughter isotope accumulates in the rock.
why some radioactive isotopes useful for measuring realatively young ages, whereas others are useful measuring older ages.
radiocarbon dating is the most powerful method of dating late Pleistoncene and Holocene artifacts.
example of how the principle of Origional Horizontality might be used to determine the order of events affecting a sequence of folded sedimentary rock
sediment accumulates in horizontal layers and we can infer tectonic forces caused tilting or folding the the sedimentary.
Principles of superpostion allow us to determine the relative ages of a sequence of folded sedimentary rocks/
sedimentary rock is oldest at the bottom and this is true of tectinic forces havent turned them upside down.
Conformable relationship in sedimentary rock
sedimentary rocks deposited without interruption.
half -life of an isotope
the time it takes for half the atoms in a radioactive samle to decompose.
tools of correlation
time correlation which equal index fossils and radiometric dating. and two Litholigic correlation - key beds.
How does Gold deposits form
transported through the earths crust dissolved in warm to hot salty water.