Robert
Lopez
Read
Harden Chapter 3, and browse through her discussion on fossils (p. 45-54).
1)
Geologists
deal with two types of ages (i.e. time).�
What are they and how do they differ?
2)
Be
able to discuss and apply the four principles used to determine relative ages.
3)
Name
four primary structures in rocks that can be used to determine if beds have
been overturned (three found in sedimentary rocks and one in lavas)?� Be able to recognize these structures in
slides.
4)
How
are �dips� of inclined beds described (two features)?
5)
What
is an unconformity, and what does an angular unconformity indicate?
6)
What
is a disconformity?
7)
What
is a nonconformity?
8)
Work
out the relative ages (youngest to oldest) of the rock units, unconformities,
and faults shown in Harden, Fig. 3-1 and 3-2, and the exercise found at this link
form more practice on relative time diagrams (I will put at least on relative
time diagram on the exam).
9)
Know,
be able to use, and arrange in order the following terms from the geological
time scale (see Harden Fig. 3-3):�
Precambrian (Hadean, Archean, Proterozoic), Phanerozoic,� Paleozoic,�
Mesozoic,� and Cenozoic.� Also know the periods of the Mesozoic
(Triassic, Jurassic, and Cretaceous) and of the last four epochs of the
Cenozoic (Miocene, Pliocene, Pleistocene, Holocene).� Know the six absolute ages for the age of Earth, base of the
Paleozoic, base of the Mesozoic, base of the Cenozoic, base of the Miocene,
base of the Pliocene, base of the Pleistocene, and base of the Holocene).
10)
What
is absolute dating based on?� Be able to
define �atomic number of element� and mass number of an isotope.� What is an isotope?� Give some examples of isotopes.
11)
Be
able to explain the concept of half-life using the example of some given number
of parent atoms with a specific half-life (e.g. one hour).� Be able to calculate the ratio of parent to
daughter atoms after some given amount of time has passed.
12)
Name
examples of parent-daughter pairs used in absolute dating, and know the
approximate half-life of the parent isotope.
13)
How
does the C-14 isotopic system work? See Figure 3-4 page 45.
14)
What
is Rancho La Brea?� What is the California
State Fossil (Latin name)?� Go to the
following the Page
Museum for more on Rancho La Brea.
Geology
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Valley College
Robert
Lopez
1)
Relative time simply deals with the order
of events; no information on how long the events lasted or the length of time
between events.
2)
Absolute time assigns absolute age to
events, usually in �years before present�.�
1 Ma = one million years before present.
3)
Superposition: in any sequence of strata
not overturned, the order of deposition is bottom to top.
4)
Original horizontality:� water-laid sediments are deposited in strata that are horizontal.
(Note:� cross beds are within beds or
strata.)
5)
Use
of inclusions:� a rock or sediment containing fragments or
other rocks must be younger than the rocks it contains.
6)
Unconformity:� a break or gap in the stratigraphic record.� Also, a hiatus; i.e. a lapse in time.
7)
The
nucleus of an atom contains protons
(+ charge) and neutrons (no charge, or you can think of a neutron as having
both a + and � charge which balance each other).
8)
Atomic number:� an element is defined by its atomic number, that is the number of
protons in the nucleus of the atom. �All
atoms of an element have the same atomic number.
9)
Atomic weight (mass number) of an atom is
the sum of its protons and neutrons.�
For example, the most common atoms of oxygen contain eight protons and
eight neutrons, and thus have an atomic weight of 16.
10)
Isotopes: atoms of an element that
contain different numbers of neutrons, and consequently, have different atomic
weights or mass numbers.
11)
Radioactive Isotopes: isotopes that spontaneously
transform into either a more stable isotope of the same element or an isotope
of a different element.� Parent isotopes
decay to daughter isotopes.
12)
Half life: time needed for the number
of parent atoms to be reduced by one-half.