Geology Reading Quiz #12 (Deep Time)

Choose the proper listing of names to fit the following three descriptionsâ Age of Mammals, Age of Dinosaurs, and longest geologic time period.

Cenozoic, Mesozoic, Precambrian

Charcoal (burned wood) that was used to make prehistoric drawings on cave walls in France was scraped off and analyzed. The results were 4 mg carbon-14 (parent isotope) and 60 mg nitrogen (daughter isotope). The half-life of carbon-14 is 5,730 years. How old are the cave drawings?

22,920 years

A radioactive isotope of the element potassium decays to produce argon. If the ratio of argon to potassium is found to be 7:1, how many half-lives have occurred?

3 half-lives

On the diagram shown, several surfaces between rock layers are identified by letters. Choose the answer below that correctly identifies the unconformities.

C and E

List the four time divisions from oldest to youngest?

Precambrian, Paleozoic, Mesozoic, Cenozoic

A corpse with flesh intact, found in the Alps in 1991, was dated by the carbon-14 method and showed a parent-daughter isotope ratio of approximately 1:1, with slightly more parent material than daughter material. The half-life of carbon-14 is 5,730 years. What is the age of the body?

The age could logically be 5,300 years.

The four columns in this diagram represent fossil-bearing sedimentary rock layers at four different sites. The sedimentary layers are continuous except at the zigzag lines, which represent unconformities. Compare the sites, determine the relative ages of the fossils, and then identify the FALSE statement.

The reptile fossils are the second-youngest fossils shown.

A hominin (human family) skull was found in a shale layer between two fine-grained igneous rock layers. There were no baked zones on the rocks above the igneous layers. The skull had been 100% fossilized and changed to stone; there was no original skull material left. On the basis of this information and the diagram, decide which of the following statements is FALSE.

The skull should be dated by the carbon-14 method, since this is the method used for organic material older than 1 million years.

Which of the following statements is FALSE? a. Scientists can date any radioactive material back only three half-lives; after this there's not enough parent material left to measure. b. Carbon-14 dating is used to date organisms, not minerals. c. Isotopic dating relies on the parent-daughter ratio. d. The "radiometric clock" starts when a radioactive mineral cools below its closure temperature.

a. Scientists can date any radioactive material back only three half-lives; after this there's not enough parent material left to measure.

Which of the following statements is FALSE? a. A formation is the name of a rock layer identified by such factors as rock type and approximate geologic age. b. An unconformity is a break in the rock record that indicates the area was underwater for millions of years. c. The generally accepted age of Earth is 4.54 billion years. d. Varieties of an element that differ only in the number of neutrons are called isotopes.

b. An unconformity is a break in the rock record that indicates the area was underwater for millions of years.

Which of the following is TRUE? a. Geologists learned how to determine numerical age long before they could determine relative age. b. Specifying the age of one feature with respect to another is called its relative age. c. Saying that a fossil is 4 million years old reports its relative age. d. Specifying the date on which an event took place is an example of relative age.

b. Specifying the age of one feature with respect to another is called its relative age.

Identify the FALSE statement. Radiometric dating a. can begin only when the isotopes cool enough to lock into the crystal lattice. b. can be used only if there is some uranium present in the rock. c. of sedimentary rock dates the time of crystallization of the sedimentary minerals, not the time of sedimentary rock formation. d. of metamorphic rock tells when the high temperatures of metamorphism cooled below the closure temperatures of the minerals involved.

b. can be used only if there is some uranium present in the rock.

Which of the following statements is FALSE? The principle of a. superposition says in a sequence of sedimentary beds, the youngest is on top. b. original continuity says sedimentary layers began as continuous expanses of sediment c. inclusions says rock containing inclusions is older than the inclusions. d. cross-cutting relations says the feature doing the cutting is younger than the feature it cuts.

c. inclusions says rock containing inclusions is older than the inclusions.

What method is used to determine the age of materials is a radiometric dating technique?

carbon dating

The boundary surface between two stratigraphic formations is called a

contact

An area of slightly dipping sedimentary rock layers has large inclusions and is intruded by an igneous dike. Apply the basic principles for determining relative ages and identify the FALSE statement. a. The sedimentary layers started out lying flat. b. The oldest sedimentary layer is the bottom layer. c. The igneous intrusion "baked" (metamorphosed) the sedimentary rock it touched. d. The dike is older than the sedimentary rock layers it cuts across.

d. The dike is older than the sedimentary rock layers it cuts across.

Which of the following is NOT a method to determine numerical age? a. carbon-14 dating b. radioactive decay of uranium to lead c. analyzing growth ring patterns in trees d. cross-cutting relations

d. cross-cutting relations

In 1815, William Smith correlated strata from many locations and plotted it on paper to show the spatial distribution of rock units on Earth's surface. This document was the first modern:

geologic map.

You should be able to number the events in the accompanying figure in the proper order of occurrence. If the first (oldest) event is number 1, and the last (most recent) is number 8, which occurred fifth in the sequence?

intrusion (batholith G)

Uniformitarianism

is illustrated by scientists' seeing pillow lava form only underwater, then theorizing that pillow lava found high in the mountains today did nevertheless form underwater.

Geologists estimate that the age of the Earth is 4.54 billion years old, based on

isotopic dating of meteorites thought to be from primitive solids of the early Solar System.

If you equate all Earth history to one calendar year, the history of our species (Homo sapiens) would occupy:

the last hour before midnight on New Year's Eve.