Q&A Hero

Q: A detrital sedimentary rock can be radiometrically dated because the clasts formed at the same time as the rock.

Q: The first life on Earth developed during the Cambrian period.

Q: Hadean is an informal term used by many geologists to refer to the earliest interval of Earth's history.

Q: The oldest rocks on Earth date back to 4.28 billion years old and were found in western Australia.

Q: Carbon-14 dating is useful for paleontologists researching dinosaurs.

Q: All isotopes are unstable.

Q: The fossil record is biased toward preserving organisms with hard parts.

Q: In cast and mold fossilization, the cast is the hollow space in the rock made when a fossil is buried in sediment.

Q: By putting events in order, scientists can use the order to determine how long ago certain geologic events took place.

Q: Numerical dating is putting events in order from first to last.

Q: What is the ultimate source for naturally occurring carbon-14? A) Cosmic ray collisions and neutron capture involving nitrogen B) Dissolution of carbonate rocks C) Decay of unstable parent isotopes to create a stable carbon-14 D) Volcanic eruption and emission of greenhouse gases

Q: In radioactive decay, an unstable ________ isotope will decay into a stable ________ isotope. A) ion; carbon B) parent; daughter C) daughter; parent D) neutron; ionized

Q: A Devonian-aged limestone contains fossils of brachiopods and bryozoans. What do these fossils indicate about the environment during the Devonian period? A) Arid desert B) Coastal swamp C) Delta D) Shallow marine

Q: Assume that a modern rabbit dies and becomes fossilized. Which of the following groups of animals would represent an accurate fossil assemblage to find with that rabbit? A) Coral, brachiopods, and fish B) Squirrels, birds, and mice C) Trilobites, brachiopods, and clams D) Fish, birds, and coral

Q: Which of the following would make the best index fossil: olenellus (522-510 million years ago), flexicalymene (~490-418 million years ago), and phacops (~418-360 million years ago). A) Olenellus B) Flexicalymene C) Phacops

Q: The white granite of the Idaho Batholith near Boise, Idaho, contains dark gray xenoliths of metamorphic material. Which is older? How do you know? A) Granite; the principle of superposition B) Xenoliths; the principle of cross-cutting relations C) Granite; the principle of unconformities D) Xenoliths; the principle of inclusions

Q: The Mississippi River cuts through Silurian-aged dolomite between northwestern Illinois and eastern Iowa. Which is older? How do you know? A) Dolomite;the principle of superposition B) Mississippi; the principle of original horizontality C) Dolomite; the principle of cross-cutting relationships D) Mississippi; the principle of lateral continuity

Q: A neutron is a combination of a(n) ________ and a(n) ________. A) cation; isotope B) nucleus; electron C) electron; proton D) ion; isotope

Q: Which two conditions are the most important in order for an organism to become fossilized? A) Rapid death and oxygen-free environment B) Rapid burial and possession of hard parts C) Rapid mineralization and rapid desiccation D) Rapid decay and possession of soft tissues

Q: In what era is the Jurassic period? A) Precambrian B) Paleozoic C) Mesozoic D) Cenozoic

Q: The ________ period on the geologic time scale is a historic name that has now largely been replaced by the Paleogene and Neogene periods. A) Carboniferous B) Hadean C) Quaternary D) Tertiary

Q: ________ is a term used to define 88% of Earth's history prior to the start of the Paleozoic era. A) Quaternary B) Precambrian C) Paleogene D) Jurassic

Q: What does "-zoic" in the eras of the geologic time scale refer to? A) Life B) Water C) Rock D) Fossilization

Q: Which era are we currently in? A) Mesozoic B) Precambrian C) Paleozoic D) Cenozoic

Q: A deposit of volcanic tuff contains the isotope potassium-40, which is slowly decaying into argon-40. How might the apparent age of the sample be affected if the volcanic tuff is heated and remains heated for a long period of time? A) The rate of decay will speed up. B) The sample will appear older than it really is. C) The sample will appear younger than it really is. D) Heat will have no effect on the age of the sample.

Q: What is the effective maximum range for carbon-14 dating? A) 100,000 years B) 70,000 years C) 10,000 years D) 13,000 years

Q: What materials are best dated with carbon-14? A) Igneous rocks B) Volcanic rocks C) Organic materials D) Sandstones

Q: You are trying to determine the age of a lava flow using an isotope with a half-life of 1.5 million years. If the sample has gone through four half-lives, what is the age of the rock? A) 1.5 million years B) 6 million years C) 375,000 years D) 5 billion years

Q: What is the half-life of potassium-40? A) 1.3 billion years B) 704 million years C) 14.1 billion years D) 4.5 billion years

Q: For what reason might the nuclei of atoms break apart in radioactivity? A) There are too many neutrons in the nucleus. B) Electrons are being shared by two adjacent atoms. C) Forces that bind protons and neutrons together are weak. D) Protons are being exchanged between atoms.

Q: Which particle of an atom will determine the atomic number of an element? A) Proton B) Nucleus C) Neutron D) Electron

Q: You are an archaeologist researching artifacts left behind by Francisco Pizzaro's conquest of Peru in the 1530s. In order to confirm the authenticity of the leather artifacts, you are performing radiometric dating using an isotope pair that has a half-life of 250 years. In order for the artifacts to date back to the time of Pizzaro's conquest, approximately how much original radioactive isotope must be left in the artifacts? A) 50% B) 25% C) 75% D) 12.5%

Q: What is the definition of a half-life? A) The parent isotope half of a radiometric dating pair B) Half the time it takes for the parent isotope to decay to the daughter C) The time it takes for half of the parent isotope to decay to the daughter D) Half of the alpha particles necessary to decay at a steady rate

Q: ________ is a technique where the decay rate of radioactive isotopes is measured and used to determine the age of a geologic material. A) Electron Capture B) Radiometric Dating C) Ion Exchange D) Half-Life

Q: If 235U has 92 protons, how many neutrons does it have? A) 25 B) 92 C) 143 D) 235

Q: What is an isotope? A) An atom that has more or fewer neutrons than it should B) An atom that has more or fewer electrons than it should C) An atom that has double the protons of a stable atom D) A nucleus of an atom that has split during the decay process

Q: What is a fossil assemblage? A) A fossil that is geographically widespread but limited to a short span of geologic time B) A fossil that is very common and existed for a long period of geologic time C) A group of fossils used to establish the age of a rock unit D) Fossil organisms that have survived multiple geologic eras

Q: What is an index fossil? A) An organism that existed for a vast period of time and is representative of an era B) An organisms that is restricted to one small, geographic setting C) A trace fossil that defines a colony of organisms D) An organism that was geographically widespread but limited to a short span of geologic time

Q: ________ was the English engineer and canal builder who observed that sedimentary strata in widely separated areas could be identified by their distinctive fossil assemblages. A) Isaac Newton B) William Smith C) Charles Lyell D) Charles Darwin

Q: Which of the following best describes the principle of faunal succession? A) Rock layers will extend equally in all directions until they pinch out or reach the edge of a basin. B) Fossil organisms succeed one another in a specific and identifiable order. C) Only the most successful organisms will survive climatic extremes. D) Faults are younger than the materials they cut across.

Q: 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? A) Rock type B) Sedimentary structures C) Fossils D) Mineral content

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

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

Q: A worm burrow is an example of which type of fossilization? A) Mummification B) Cast and mold C) Carbonization D) Trace fossil

Q: When a shell is buried in sediment and subsequently dissolved, a cavity called a ________ is left behind. When this cavity is later filled with sediments, a ________ is created. A) mold; gastrolith B) trace; burrow C) mold; cast D) amber; carbonization

Q: Which of the following is an example of a trace fossil? A) A spider encased in amber B) Petrified wood C) Gastroliths D) A skeleton

Q: A black, organic residue of an ancient fern would be an example of which type of fossilization? A) Permineralization B) Mummification C) Replacement D) Carbonization

Q: ________ is the scientific study of fossils. A) Quaternary geology B) Volcanology C) Geomorphology D) Paleontology

Q: What is a fossil? A) Evidence of past life that can include skeletal as well as trace material B) Only the hard parts of a skeletal structure that have been preserved C) Mudcracks preserved in sedimentary rock D) A really old geologist

Q: When rocks are ________, several adjacent layers were deposited without interruption. A) included B) dissolved C) conformable D) cross-cut

Q: What is the definition of an inclusion? A) A fossil of an organism that existed for a short period of geologic time B) A fragment of one rock unit enclosed in another rock unit C) An unstable isotope decaying into a stable form D) A fault bisecting a layer of rock

Q: What scientific development made accurate numerical dating possible? A) Discovery of radioactivity B) Correlation of rock layers C) Development of radar D) Discovery of X-rays

Q: Which of the following is an example of a relative date? A) The Cenozoic era began sixty-five million years ago. B) A headstone in a cemetery has the date a person died. C) The Declaration of Independence was written in 1776. D) The Silurian period came before the Devonian period.

Q: Which of the following is an example of a numerical date? A) The Stone Age occurred before the Iron Age. B) John Adams was president of the United States after George Washington. C) A meteorite impacted the Earth sixty-five million years ago. D) Dinosaurs descended from reptiles, which descended from amphibians.

Q: A(n) ________ is a type of unconformity with parallel beds above and below the erosional surface. A) fossil conformity B) nonconformity C) disconformity D) angular unconformity

Q: Which scientist is credited with developing the law of superposition? A) James Ussher B) Charles Lyell C) James Hutton D) Nicholas Steno

Q: What is the definition of relative dating? A) Putting events in order from first to last B) Using radioactive materials to determine an age C) Counting tree rings to determine an age D) Calculating dates based on the theory of relativity

Q: What kind of temperature and pressure conditions will exist in a burial metamorphism environment? A) Low temperature and low pressure B) Low temperature and high pressure C) High temperature and low pressure D) High temperature and high pressure

Q: Which of the following environments would most likely produce metamorphism in fault zones? A) Great depth and low temperatures B) Shallow depth and low temperatures C) Great depth and high temperatures D) Shallow depth and high temperatures

Q: ________ metamorphism will occur when high-speed projectiles strike the Earth's surface. A) Fault zone B) Shock C) Subduction zone D) Contact

Q: Why is quartz a bad mineral to use to determine a metamorphic environment? A) Because it is not common in metamorphic rocks B) Because silicate minerals do not metamorphose C) Because quartz is stable over a wide range of metamorphic settings D) Because it can only be used in hydrothermal metamorphism

Q: Metamorphic facies derive their names from those metamorphic rocks specifically formed from a ________ parent. A) basaltic B) granitic C) shale D) obsidian

Q: ________ metamorphism will occur where two blocks of rock are grinding against each other. A) Impact B) Regional C) Hydrothermal D) Fault zone

Q: What is the source of water for hydrothermal metamorphism? A) Groundwater percolating from the surface B) Fluids coming off magma plutons C) Black smokers sucking seawater into the subsurface D) Groundwater from the surface and fluids from magma plutons

Q: ________ metamorphism is responsible for the emplacement of metallic ore veins. A) Contact B) Burial C) Hydrothermal D) Subduction zone

Q: Why will metamorphic rocks found in a contact metamorphism aureole be nonfoliated? A) Because the main agent of metamorphism is heat, which will result in intergrown crystals B) Because the pressures involved with contact metamorphism destroy foliated crystals C) Because the temperatures associated with this are too low to alter the rock D) Because the velocity of the hydrothermal fluids will carry foliated materials away

Q: Which of the following can be a parent rock for gneiss? A) Shale B) Granite C) Schist and phyllite D) Marble and shale E) Shale, granite, schist, and phyllite

Q: ________ can produce intricately folded rocks. A) Differential stress B) Confining pressure C) Heat D) Hydrothermal fluids E) Cold surface water

Q: Olivine can be converted to spinel through ________. A) directed pressure B) heat C) hydrothermal fluids D) confining pressure

Q: What is the most important factor driving metamorphism? A) Pressure B) Heat C) Hydrothermal fluids D) Orientation

Q: Can parent rock features such as sedimentary structures and fossils survive low-grade metamorphism? A) Yes, because the shells of the organisms are strong enough to withstand directed pressure. B) No, because the sediments and organic materials will be melted. C) Yes, because such features can withstand low temperatures and pressures but will be destroyed in higher metamorphic grades. D) No, because even low-grade pressure is too much for such delicate features.

Q: Along which type of tectonic boundary will greenschists and blueschists form? A) Transform B) Convergent C) Divergent D) Failed rift zone

Q: A(n) ________ facies is associated with a high-pressure, low-temperature environment. A) zeolite B) granulite C) blueschist D) eclogite

Q: Which of these mineral assemblages is characteristic of a greenschist facies? A) Potassium feldspar, biotite, and quartz B) Chlorite, epidote, and serpentine C) Hornblende D) Quartz and muscovite

Q: Which of the following is a metamorphic facies? A) Kaolinite B) Staurolite C) Eclogite D) Quartzite

Q: What is a metamorphic facies? A) A rock that forms at specific metamorphic conditions and can be used to determine the metamorphic style B) Textural transitions based on the direction and amount of pressure C) Zones of contact metamorphism along an intrusive igneous rock D) An assemblage of minerals that form in very similar metamorphic environments

Q: ________ are materials that are good indicators of the metamorphic environment in which they formed and can be used to distinguish between various zones of metamorphism. A) Index fossils B) Index minerals C) Blueschists D) Aureoles

Q: Which tectonic boundary is associated with regional metamorphism? A) Convergent B) Divergent C) Dip-slip D) Transform

Q: Which of the following materials is most closely associated with shock metamorphism and meteorite impact sites? A) Slate B) Blueschist C) Gneiss D) Tektites

Q: ________ is a widespread type of metamorphism typically associated with mountain building. A) Pyrometamorphism B) Burial metamorphism C) Shock metamorphism D) Regional metamorphism