Geotime

Beta (β) decay: [For example, 234Th90 → 234Pa91]

decay: When an atom undergoes beta decay, a neutron in the nucleus of an unstable atom is converted into a proton and an electron. The electron is then emitted. During this process, the atomic mass number remains the same and the atomic number increases by 1.

A(n) __________ exhibits sedimentary layers that are parallel to each other above and below an erosive surface. Hints angular unconformity conformable succession disconformity intrusive contact nonconformity

disconformity

Which organism from the video is the least useful for relative dating? Hints sycamore leaf scallop dinosaur fern

scallop

The sedimentary layers above an erosive surface are __________ relative to all rocks present below the surface. Hints dipping eroded younger the same age older

younger

After four half-lives of decay, what is the ratio of radioactive parent isotope to stable daughter isotope? Hints 1:15 1:31 1:3 1:7 1:1

1:15

What is the accepted age of the Earth? 1 million years 4.6 billion years 10,000 years 4.6 million years

4.6 billion years

What are the characteristics of an index fossil? Hints preserved as a mold limited to a short span of geologic time but widely distributed geographically limited found only in shale large enough to see without a hand lens

limited to a short span of geologic time but widely distributed

Two isotopes of uranium, 238U and 235U, have the same number of ___, but different numbers of ___. Hints protons; neutrons neutrons; electrons electrons; protons neutrons; protons protons; electrons

protons; neutrons

An isotope sample initially weighing 500 grams decays to produce a daughter element. What is the amount of parent element remaining after two half-lives? Hints 62.5 grams 250 grams 125 grams 1000 grams 500 grams 150 grams [Assuming the half-life of a sample is 4 months, then in 4 months there will be 0.5 gram of the parent element left and 0.5 gram of the daughter element will be produced; In month 8 (which is two half-lives), there will be only 0.25 gram of the parent element and 0.75 gram of the daughter element; that is, one-fourth of the parent sample (in red) is left; And month 12, there is only one-eighth of the parent element.]

125 grams

Each isotope has a unique half-life. The half-life of an isotope is the time taken for half of the starting quantity to decay (with a ratio of 1:1). After two half-lives, there will be one-fourth of the original parent sample and three-quarters would have decayed to the daughter product (with a ratio of 1:3). After three half-lives, the ratio becomes 1:7, and so forth. A graph showing months on the x-axis and the amount of parent/daughter on the y-axis. The graph uses four pie charts to demonstrate how parent elements and daughter elements change with each half life for a sample in increments of 4 months. The graph, for instance, shows that assuming the half-life of a sample is 4 months, then in 4 months, there will be 0.5 gram of the parent element and 0.5 gram of the daughter element will be produced. In month 8 (which is two-half-lives), there will be only 0.25 gram of parent element left and 0.75 gram of daughter element; that is, one-fourth of the parent sample (in red) is left, and in month 12, there is only one-eighth of the parent element. You attend a geology lab where you are asked to estimate the age of a fossil. The ratio of parent to daughter elements in the fossil sample is 1:7. You know that fossils are the remains of living organisms, which have some amount of C-14 isotope. The C-14 isotope, which has a half-life of 5730 years, begins to decay as the organism dies. What would be your estimation of the fossil's age? 2865 17,190 5730 11,460 40,110 22,920

17,190 [[[[Correct]]] When a living organism dies, it stops taking in new carbon. The ratio of C-12 to C-14 at the moment of death is the same as every other living organism, but the C-14 decays and is not replaced. The C-14 has a half-life of 5730 years, whereas the amount of C-12 remains constant in the sample. By looking at the ratio of C-12 to C-14 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of a fossil.

If one half-life has lapsed, what is the radioactive parent to stable daughter isotope ratio? Hints 13:87 75:25 6:94 50:50 25:75

50:50

If a rock contains ten different kinds of fossils, which of the following must be true? Hints All ten organisms evolved at the same time. All ten organisms went extinct at the same time. All of the fossils are useful in constraining relative age. All of the organisms had to be alive when the rock was deposited. These organisms give the minimum age of the rock.

All of the organisms had to be alive when the rock was deposited.

Carbon-14 dating Egyptian mummies volcano ash wood piece granite gneisses

All organic materials contain carbon and are dated using C-14.... -Egyptian mummies -wood piece

What characteristic most directly DISTINGUISHES an angular unconformity from a nonconformity? Hints Angular unconformities represent missing time, whereas nonconformities do not. Conformities represent missing rock layers. Angular unconformities separate rock layers along nonparallel surfaces. Nonconformities separate two different rock types, whereas angular unconformities form only between strata of the same rock type. Nonconformities separate parallel rock layers of the same rock type.

Angular unconformities separate rock layers along nonparallel surfaces.

Five layers of rock are cut by two faults. Both faults cut through all five layers of rock. Fault A breaks through to the surface, whereas fault B does not. Which of the following statements about faults A and B is most accurate? Fault A is younger than fault B, and both are older than the five layers of rock. Faults A and B are about the same age, and both are younger than the five layers of rock. Fault A is younger than fault B, and both are younger than the five layers of rock. Faults A and B are about the same age, and both are older than the five layers of rock.

Fault A is younger than fault B, and both are younger than the five layers of rock.

What is the principle of cross-cutting relationships? Geologic features that cut through rocks must form at roughly the same time as the rocks that they cut through. Geologic features that cut through rocks must form before the rocks that they cut through. Geologic features that cut through rocks must form after the rocks that they cut through.

Geologic features that cut through rocks must form after the rocks that they cut through.

Electron capture: [For example, 59Ni28 → 59Co27]

In this form of radioactive decay, the nucleus of an atom absorbs an inner atomic electron and converts a proton into a neutron. During electron capture, the atomic mass number remains the same but the atomic number decreases by 1.

What is stratigraphic correlation? Putting events in order from first to last Matching up rocks of similar age in different regions Matching up continental coasts based on matching shapes Dividing up rock layers into new ones based on mineral content

Matching up rocks of similar age in different regions

The Jurassic Period lies in the _____ Era, which was dominated by large terrestrial vertebrates, or _____. Hints Mesozoic; dinosaurs Proterozoic; mammals Paleozoic; trilobites Oligocene; horses Cenozoic; humans

Mesozoic; dinosaurs

Which of the following statements regarding radioactive decay is true? Hints A mineral starts out with a parent:daughter isotope ratio of 75:25. More parent isotopes accumulate over time. The nucleus of a radioactive particle is not affected. The number of half-lives decreases over time. More daughter products accumulate over time.

More daughter products accumulate over time.

Which of the following statements about relative and absolute age dating is most accurate? Relative age dating places rocks and events in chronological order but does not provide information about absolute age. Relative age dating provides information about absolute ages but does not place rocks and events in chronological order. Relative age dating places rocks and events in chronological order and can provide information about absolute age. Relative age dating does not provide information about absolute ages, nor does it place rocks and events in chronological order.

Relative age dating places rocks and events in chronological order but does not provide information about absolute age.

What is the principle of original horizontality? Metamorphic rocks are close to horizontal when eroded. Sedimentary rocks are close to horizontal when deposited. Metamorphic rocks are close to horizontal when deposited. Sedimentary rocks are close to horizontal when eroded.

Sedimentary rocks are close to horizontal when deposited.

Why is the geologic time scale more detailed in the Phanerozoic than in previous eons? Hints The Phanerozoic Eon is more detailed because of the presence of organisms with hard parts and the rapid increase in biodiversity. Rocks that were formed in the Precambrian were destroyed by processes of the rock cycle. Humans did not exist until the very last part of Earth history. The Phanerozoic Eon is more detailed because of numerical ages obtained from the breakdown of radioactive isotopes.

The Phanerozoic Eon is more detailed because of the presence of organisms with hard parts and the rapid increase in biodiversity.

A radioactive element undergoes decay via the loss of two alpha particles to form a stable daughter isotope. Following the decay, what would the atomic number of this newly created stable isotope be? Hints The atomic number of the daughter isotope would be 16 units less than the original parent isotope. The atomic number of the daughter isotope would be two units less than the original parent isotope. The atomic number of the daughter isotope would be four units more than the original parent isotope. The atomic number of the daughter isotope would be four units less than the original parent isotope. The atomic number of the daughter isotope would be eight units less than the original parent isotope.

The atomic number of the daughter isotope would be four units less than the original parent isotope.

A fault (F) breaks three layers of sedimentary rock (S). An igneous intrusion (I1) has broken through the bottommost layer of rock. A second igneous intrusion (I2) has moved up the fault and pooled on top of the uppermost layer of rock. Which event would be considered the youngest? The intrusion of I2 is the youngest event. We can know this because I2 sits on top of all other rocks. Deposition of the three sedimentary layers, S, is the youngest event. We know this because the fault underlies the igneous rocks. Faulting of rock along F is the youngest event. We know this because all three layers of sedimentary rock have been broken. The intrusion of I1 or I2 is the youngest event. Without more information, we cannot know which igneous rock is youngest.

The intrusion of I1 or I2 is the youngest event. Without more information, we cannot know which igneous rock is youngest.

Using a calendar year as an analogy to the geologic time scale, when do the oldest anatomically modern humans appear on Earth? Hints The oldest human fossils show up at about eleven minutes to midnight on December 31st. The oldest human fossils show up when animals and plants move out of the sea and onto land in late November. The oldest human fossils are found in late March, which represents the Precambrian on the geologic time scale. The oldest human fossils show up between December 15th and 26th in the Mesozoic Era. The oldest human fossils appear in mid-November, which is the beginning of the Phanerozoic Eon.

The oldest human fossils show up at about eleven minutes to midnight on December 31st.

What is the best definition of fossil range? Hints The variety of organisms that occur together in a rock unit. The total number of organisms alive at one time in the geologic record. The time when an organism goes extinct. The period of time when an organism first and last appears in the sedimentary record. The geographic area over which an organisms thrives.

The period of time when an organism first and last appears in the sedimentary record.

How is the geologic time scale related to the fossil record? Hints The fossil record is not related to the geologic time scale. The Precambrian was defined using fossil organisms. Radiometric dating of organisms was used to build the time scale. The time scale is only built on times when organisms went extinct. The periods of the time scale were constructed based on ranges of fossil organisms.

The periods of the time scale were constructed based on ranges of fossil organisms.

In the field you encounter a sequence of sedimentary rocks that has a dike running through them. A normal fault crosses the entire sequence, cutting off part of the dike near the surface. Which scenario best describes your observations? (All scenarios list events from oldest to youngest.) Hints The relative ages of the sequence are as follows: dike > normal fault > sedimentary rocks. The relative ages of the sequence are as follows: normal fault > dike > sedimentary rocks. The relative ages of the sequence are as follows: sedimentary rocks > dike > normal fault. The relative ages of the sequence are as follows: sedimentary rocks > normal fault > dike. The relative ages of the sequence are as follows: normal fault > sedimentary rocks > dike.

The relative ages of the sequence are as follows: sedimentary rocks > dike > normal fault.

Radioactive decay in mineral shows that two half-lives have elapsed, giving an age of approximately 1.4 billion years. Using the table in the video as a reference, what is the correct radioactive parent and stable daughter isotope pair? Hints K40, Ar40 Th232, Pb208 U235, Pb207 Rb87, Sr87 U238, Pb206

U235, Pb207

Name the epoch, period, era and eon in which we currently live. Hints We live in the Cretaceous Period of the Mesozoic Era and Phanerozoic Eon. We live in the Archean Eon, which is part of Precambrian time. We live in the Cambrian Period at the beginning of the Phanerozoic Eon. We live in the Holocene Epoch of the Quaternary Period, which is part of the Cenzoic Era and Phanerozoic Eon. We live in the Eocene Epoch of the Paleogene Period, which is part of the Cenzoic Era and Phanerozoic Eon.

We live in the Holocene Epoch of the Quaternary Period, which is part of the Cenzoic Era and Phanerozoic Eon.

Alpha (α) decay [For example, 238U92 → 234Th90]

When an atom undergoes alpha decay, it gives off an alpha particle made up of two protons and two neutrons that come directly from its nucleus. During this process, the atomic mass decreases by 4 and the atomic number decreases by 2. The atomic mass of both parent and daughter elements is a superscript to the left of the elements and the atomic number is a subscript to the right. For example, 238U92 → 234Th90

What is the principle of superposition? Within a sequence of rock layers formed at Earth's surface, rock layers in the middle of a sequence are older. Within a sequence of rock layers formed at Earth's surface, rock layers lower in the sequence are older. Within a sequence of rock layers formed at Earth's surface, rock layers higher in the sequence are older.

Within a sequence of rock layers formed at Earth's surface, rock layers lower in the sequence are older.

What does the term unconformity mean? Hints an extra rock layer that represents a period of deposition a missing rock layer in a sequence that represents a period of erosion or nondeposition a missing rock layer in a sequence that represents a period of deposition an extra rock layer that represents a period of erosion

a missing rock layer in a sequence that represents a period of erosion or nondeposition

Which of the following includes all common types of radioactive decay? Hints atomic number, beta particle emission, electron capture alpha particle emission, beta particle emission, half-life alpha particle emission, beta particle emission, radioactive parent isotope alpha particle emission, beta particle emission, electron capture alpha particle emission, stable daughter, electron capture

alpha particle emission, beta particle emission, electron capture

How is the atomic number of an atom determined? Hints counting the number of atoms of an element in a mineral counting the number of protons circling the nucleus counting the number of protons and neutrons in the nucleus counting the number of neutrons in the nucleus counting the number of protons in the nucleus

counting the number of protons in the nucleus

Following the deposition of a sequence of sedimentary rocks, which event is the first to occur to produce an angular unconformity? Hints deformation deposition weathering intrusion erosion

deformation

Which is an example of radioactivity that occurs when a neutron is converted to a proton and an electron is emitted from the nucleus? Hints electron capture nuclear fission emission of a beta particle magmatic fractionalization emission of an alpha particle

emission of a beta particle

What is the category name for the largest division of time used on the geologic time scale? Hints Eon Period Epoch Era

eon

Which of the following is a common feature that all unconformities exhibit? Hints dipping rocks erosive surface folded rocks igneous rocks intrusions

erosive surface

The principle of ________ states that organisms succeed one another in a definite, determinable order that can be used to recognize a specific time period. fossil succession superposition correlation lateral continuity

fossil succession

When correlating rock between widely separated areas or between continents, what feature(s) do geologists rely on the most to link distant rock units of similar age? Fossils Mineral content Sedimentary structures Rock type

fossils

U-235 dating Egyptian mummies volcano ash wood piece granite gneisses

inorganic materials are dated using any radioactive element, such as uranium, rubidium, potassium, and thorium, except carbon. -volcano ash -granite -gneisses

What term describes an erosional surface bounded above by flat-lying sedimentary rocks and below by igneous or metamorphic rocks? Hints disconformity nonconformity paraconformity angular unconformity inclusion

nonconformity

Which process is not a common form of natural radioactive decay? Hints emission of alpha particles electron capture nuclear fission emission of beta particles

nuclear fission

Which of the following characteristics is the most desirable for constraining the relative age of rocks? Hints organisms with overlapping ranges and geologically short lifespans organisms that do not overlap in range organisms that overlap in range and are geologically long-lived organisms that are soft-bodied and microscopic in size organisms that span long periods of geologic time

organisms with overlapping ranges and geologically short lifespans

The fact that sedimentary rocks are almost always deposited in a horizontal position reflects which law or principle of geology? Hints superposition uniformitarianism fossil succession inclusions original horizontality

original horizontality

Which material, principle, or process enables a method of numerical dating? Hints inclusions superposition cross-cutting fossils radioactivity

radioactivity

Which principle or law of geology states that in a sequence of undeformed sedimentary rocks, each bed is older than the one above? Hints uniformitarianism original horizontality superposition evolution cross-cutting relationships

superposition

Which principle of relative age dating is important for determining the relative age of igneous rock that has intruded into overlying rock? the principle of intrusive relationships the principle of original horizontality the principle of superposition the principle of cross-cutting relationships

the principle of cross-cutting relationships

While working in the field, you encounter an outcrop in which sandstone, shale, and limestone have been intruded by a basaltic dike. You know that the basaltic dike is younger than the sedimentary rock by applying which law or principle? Hints the law of superposition the principle of cross-cutting relationships the principle of fossil succession the principle of inclusions the principle of original horizontality

the principle of cross-cutting relationships

Which of the following is an accurate description of a nonconformity? Hints younger horizontal sedimentary rocks overlie an erosive surface, with older parallel sedimentary rocks present below an igneous intrusion that causes sedimentary layers to uplift and erode horizontal sedimentary rocks that have been laid down without interruption younger sedimentary strata overlie uplifted and weathered igneous or metamorphic rocks younger, relatively flat-lying sedimentary rocks overlie older, tilted sedimentary rocks

younger sedimentary strata overlie uplifted and weathered igneous or metamorphic rocks