Numeric and Relative Dating - Essay Example

GEOL 1022: ASSIGNMENT Answer all the following questions Distinguish between numeric and relative dating. Numerical dating establishes how many years ago a given event took place. This dating method is based on the decay of naturally occurring radioactive elements. On the other hand, relative dating places historical events in their correct order but fails to provide numerical estimates of how many years ago the events took place.2. If sedimentary layers (beds) are steeply inclined in an exposure (outcrop) of rock, what principle allows you to assume that the beds were tilted after they were deposited?

Principle of Superposition - basically each layer (strata) of rock is younger than the layer below it. However, since the strata are steeply dipping, one would need to determine which way is up as the strata could be overturned. 3. How do index fossils allow us to determine the relative ages of rock strata? The principle of faunal succession is one concept that makes it easy to use index fossils to determine the relative ages of rock strata. This principle states that different fossil species always appear and disappear in the same order and that once a fossil species goes extinct, it disappears and cannot reappear in younger rocks (Prothero & Buell, 2007).

In this principle, if an unidentified fossil is found in the same rock layer as an index fossil, the two species must have existed during the same period of time. If the same index fossil is found in different areas, the strata in each area were likely deposited at the same time. Thus, the principle of faunal succession makes it possible to determine the relative age of unknown fossils and correlate fossil sites across large discontinuous areas. 4. Is there one place on Earth where we can see the complete geologic column?

Critical evaluation of this geological concept reveals a lot of assumptions and misconceptions which rule out the possibility of the existence of this feature. Though faunal succession has been supported to be a reality, close examination indicates that even with the ten systems superposed, the column has never been observed (Prothero & Buell, 2007). Research establishes that index fossils rarely overlie each other, especially in the same locality. In that respect, even in places where Phanerozoic systems have been employed, this column’s existence is still considered hypothetical.5. What is meant by the term correlation, and why are fossils such powerful tools in correlating strata over great distances?

Correlation is the concept of piercing together separated outcrops of informational content. In this technique, information obtained from two outcrops is integrated and the resultant time interval is greater than for each of them. The sequence of fossils through the rock layers is a powerful tool since the fossils representing each age are always consistent, whereas the rock layers change across distances (Prothero & Buell, 2007). This makes it easy to use them in mapping distinctive formations of the fossils hence making fossils such powerful tools in correlating strata over great distances.6. What kinds of rocks—igneous, sedimentary, or metamorphic—are best for radiometric dating? Why? Of the three basic rock types, igneous rocks are most suited for radiometric dating.

Igneous rocks can readily be melted with extreme heat and pressure hence suitable for radiometric dating which works on the idea that when rocks are in liquid form, their radiometric clock resets (Prothero & Buell, 2007). Although sedimentary rocks cannot be dated using this technique, laws of superposition and crosscutting relationships can be applied to place absolute time limits on layers of sedimentary rocks crosscut and estimate their age. 7. During the process of radioactive decay, a hypothetical atom lost two protons and two neutrons from its nucleus.

The original atom had an atomic number of 10 and an atomic mass of 28. Do the following: What is the new atomic number of the atom (after that loss)? Original atomic number (protons) = 10Atomic mass (Protons + Neutrons) = 28Neutrons = 18Therefore new atomic number will be = 8 What is the new atomic mass number of the atom (after that loss)? New atomic mass number = 248. If radioactive decay began with 400,000 parent isotopes, how many would be left after three half-lives? 200,000 b. 50,000 c. 100,000 d. 25,0009. The half-life of a radioactive isotope is 500 million years.

Scientists testing a rock sample discover that the sample contains three times as many daughter atoms as parent isotopes. What is the age of the rock? 5500 million b. 1,000 million years c. 1,500 million years d. 2,500 million years10. If a radioactive element has a half-life of 16 million years, what fraction of the original amount of parent material will remain after 96 million years? What percentage will that be? N (number of half-lives) = Total time/ Half-life N = 96/16 = 6 Final amount= (½)n = (½)6The fraction of the original amount of parent material will remain after 96 million years = 1/64