Geology Ch. 9 Test

The statement is true because the term "Paleozoic" refers to a specific era in Earth's history, which lasted from about 541 to 252 million years ago. This era is characterized by the presence of ancient life forms, including early fish, amphibians, reptiles, and the first appearance of complex plant life. The prefix "paleo-" means ancient or old, and "zoic" refers to life, so the term Paleozoic literally means "ancient life." Therefore, it is accurate to say that the term Paleozoic describes the era of ancient life forms.

Rapid burial and possession of hard parts are necessary conditions for the preservation of plant or animal remains as fossils. This is because rapid burial protects the remains from being destroyed or decomposed by external factors such as scavengers, weathering, or erosion. Additionally, hard parts like bones or shells are more likely to survive the fossilization process compared to soft tissues. Therefore, both rapid burial and possession of hard parts increase the chances of plant or animal remains being preserved as fossils.

The law of superposition states that in a horizontal sequence of conformable sedimentary strata, each higher bed is younger than the bed below it. This means that the oldest rocks are found at the bottom, while the youngest rocks are found at the top. This principle is based on the observation that sedimentary layers are deposited in a chronological order, with each new layer being added on top of the previous layers over time. Therefore, the law of superposition helps geologists determine the relative ages of different rock layers and the fossils found within them.

The statement is true because in the Proterozoic era, which spanned from 2.5 billion to 541 million years ago, fossils are rare or absent. This makes it difficult to determine the age of rocks and geological events using traditional fossil dating methods. However, numerical age dating based on radioactivity provides a reliable way to determine the age of Proterozoic rocks and study the geologic history of this era.

The correct answer is "beds l and 3 are older than bed 4". This statement is true because it states that both bed 1 and bed 3 are older than bed 4. This is possible because in sedimentary rock layers, the oldest layer is usually found at the bottom, and each subsequent layer is younger than the one beneath it. Therefore, if bed 1 is the lowest bed and bed 4 is above it, it is logical to conclude that bed 1 is older than bed 4. Similarly, if bed 3 is also older than bed 4, the statement is true.

Marine sedimentary strata of the same age on different continents can usually be correlated by their fossil assemblages. This is because fossils found in sedimentary rocks provide evidence of the organisms that lived during a particular time period. By comparing the fossil assemblages in different sedimentary strata, scientists can determine if they are of the same age and therefore correlate them. This correlation is possible because many marine organisms have a wide geographic distribution and their fossils can be found in different parts of the world. Therefore, the statement is true.

The statement is true because the term Mesozoic does refer to life forms that are intermediate in complexity between early and much later, more modern-looking life forms. The Mesozoic era is commonly known as the Age of Dinosaurs and it lasted from about 252 to 66 million years ago. During this time, there was a significant diversification and evolution of various life forms, including dinosaurs, mammals, birds, and flowering plants. These life forms represented a transition from simpler early life forms to more complex and modern-looking organisms.

The explanation for the given correct answer is that the geologic time scale was indeed devised before numerical dating using radioactivity was invented. The geologic time scale is a system of chronological dating that classifies and organizes Earth's history into different time periods based on major geological and biological events. It was developed in the 19th century by geologists who relied on relative dating methods such as the law of superposition and fossil correlation. It was only in the early 20th century that the discovery of radioactivity and its application in radiometric dating allowed for more precise numerical dating of geological events.

Potassium-40 is a radioactive isotope that undergoes a process called radioactive decay. During this decay, it transforms into argon-40, which is a stable daughter product. This transformation occurs over time as the radioactive isotope loses particles and energy. Therefore, it is correct to say that potassium-40 has argon-40 as a daughter product.

The statement is true because the Paleocene is indeed the oldest epoch of the Tertiary period. The Tertiary period is divided into several epochs, with the Paleocene being the first one. It began approximately 66 million years ago and lasted for about 9 million years. During this epoch, there were significant changes in climate and the diversification of mammals. Therefore, the statement is correct.

Correlation refers to the investigative process by which geologists identify and match sedimentary strata and other rocks of the same ages in different areas. This process involves comparing the characteristics and composition of rocks in different locations to determine their relative ages and establish connections between them. By correlating rocks, geologists can gain insights into the geological history of an area and understand how different rock formations are related to each other.

A disconformity is a type of unconformity where there is a break in the rock record, but the layers or strata above and below the unconformity are parallel to each other. This means that the rock layers were deposited horizontally, and then there was a period of erosion before more layers were deposited on top. Therefore, the statement that a disconformity is an erosional unconformity with parallel beds or strata above and below is true.

An angular unconformity is a type of erosional contact between tilted, older strata below and horizontal, younger strata above. This means that the layers of rock below the unconformity were tilted or folded before being eroded, and then new layers of rock were deposited horizontally on top of the eroded surface. This creates a distinct angular relationship between the older and younger strata, forming an angular unconformity.

An angular unconformity is characterized by tilted strata below the unconformity, indicating a period of deformation or tilting of the rock layers. The bedding in the younger strata above the unconformity is parallel to the unconformity, suggesting that deposition resumed after the period of tilting. This type of unconformity represents a gap in the geologic record where erosion and uplift occurred before new layers were deposited.

The Cambrian period began approximately 540 million years ago. This period is known for the appearance of complex, invertebrate life forms, which are commonly found as fossils in marine strata from this time period.

Most scientists today accept that the age of the Earth is approximately 4.5 billion years. This estimation is based on various scientific methods, such as radiometric dating of rocks and minerals, which provide evidence for the Earth's age. These methods involve measuring the decay of radioactive isotopes and calculating the time it takes for them to reach their present state. The consensus among scientists is that the Earth formed around 4.5 billion years ago, making this answer the most widely accepted.

The principle of faunal succession is the idea or concept that ancient life forms succeeded each other in a definite, evolutionary pattern and that the contained assemblage of fossils can determine geologic ages of strata. This principle is based on the observation that different fossil assemblages are found in different layers of rock, and by comparing these assemblages, scientists can determine the relative ages of the rocks. It is a fundamental principle in stratigraphy and is used to establish the relative ages of rocks and the fossils they contain.

Nicolaus Steno made the first clear statement of the law of superposition in the 17th century.

The correct answer is "surface of erosion separating younger strata above from older strata below." An unconformity is a geological feature where there is a gap in the rock record due to erosion or non-deposition. In this case, the unconformity is characterized by a surface of erosion that separates younger layers of rock above from older layers of rock below.

The term "zoic" in the context of the geologic time scale refers to life and living things. This suggests that the era being referred to is characterized by the existence and development of various forms of life on Earth.

Petrification refers to the process of fossilization where the internal cavities and pores of the original organism are filled with precipitated mineral matter. This process replaces the organic material with minerals, preserving the original structure of the organism.

Uranium-238, uranium-235, and thorium-232 are all radioactive isotopes that undergo radioactive decay over time. This decay process involves the transformation of the parent isotopes into different, stable daughter isotopes. In this case, the correct answer is lead, as uranium-238 and thorium-232 decay into various isotopes of lead, while uranium-235 decays into isotopes of thorium and protactinium before eventually reaching lead through a series of decay steps.

The feldspar and quartz contents of a granite would not directly contribute to working out the sequence of geologic events in an area because the composition of minerals within a rock does not provide information about the relative timing or order of events. Instead, it is the physical relationships between different rock units, such as inclusions of sandstone in a granite pluton or an unconformity between a granite and sandstone, that can help determine the sequence of geologic events.

The correct answer is eon, era, period, epoch. This is the correct order of decreasing lengths of time in the geologic time scale. Eons are the longest divisions of time, followed by eras, periods, and then epochs, which are the shortest divisions.

Paleophrenology is not the study of fossils and ancient life forms. It is a term that does not exist in the field of science. The correct answer is false because there is no such study or field called paleophrenology.

The Mississippian and Pennsylvanian periods are combined into the Carboniferous period in Europe and elsewhere.

The half-life of carbon-14 is 6000 years, meaning that after 6000 years, half of the original carbon-14 in a sample will have decayed. Since the sample of charcoal was formed 15000 years ago, three half-lives have passed. This means that (1/2)^3 or 1/8th of the original carbon-14 would remain today. Therefore, the correct answer is between one-fourth and one-eighth.

The ratio of parent to daughter isotopes in a radioactive decay process is 0.40. This means that for every 0.40 parent isotopes, there are 0.60 daughter isotopes. Since the parent isotopes are decreasing over time due to decay, and the ratio is less than 1, it indicates that some decay has occurred. Therefore, at least one half-life has elapsed since the material was 100% parent atoms. However, since the ratio is less than 0.50, it suggests that less than two half-lives have passed. Therefore, the answer is between 1 and 2 half-lives.

Radon-222 is a radioactive daughter of the U-238 decay series that can accumulate to unhealthful levels in poorly ventilated uranium mines and home basements. Radon-222 is a colorless and odorless gas that is formed as uranium-238 undergoes radioactive decay. It is a known carcinogen and prolonged exposure to high levels of radon-222 can increase the risk of developing lung cancer. Therefore, it is important to regularly test for radon levels and take necessary measures to mitigate its concentration in indoor spaces.

The statement is false because an angular unconformity occurs when older, tilted layers of rock are eroded and then younger, horizontal layers are deposited on top of them. In this case, the strata above the angular unconformity were not tilted before erosion, but rather were deposited horizontally after the erosion of the older strata.

The statement is false because correlation of rock units between continents or widely separated areas is not accomplished solely by using physical features such as color, texture, and thickness of units. It also involves the study of fossils, paleomagnetism, and other geological evidence to determine the age and relationship of rock units across different areas.

An essential characteristic of an index fossil is that the organism only lived for a short period of geologic time. This is because index fossils are used to identify and correlate the age of rock layers. By knowing the specific time range in which an organism existed, scientists can use the presence of that fossil in a rock layer to determine the relative age of the rocks. If the organism lived for a long period of time, it would not be as useful for dating purposes.

The correct answer is one millionth. This is because the recorded history of man, which stretches back 4600 years before the present, is a very small fraction compared to the total geologic time, which spans billions of years.

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After three half-lives, only one-eighth (not one-ninth) of the original radioactive parent isotope remains, while seven-eighths (not eight-ninths) has decayed into the daughter isotope.

The statement is suggesting that the granite intruded the sedimentary beds because pebbles of granite are found in sandstone and conglomerate that are resting on the granite. However, the correct answer is False. This means that the statement is incorrect and the granite did not intrude the sedimentary beds.

Iridium has been implicated in the extinction of the dinosaurs at the end of the Cretaceous Period.

If the sandstone contains pebbles of the granite, it indicates that the granite was present and eroded before the sandstone was formed. This suggests that the granite is older than the sandstone.

Sedimentary rocks are generally difficult to date using radiometric methods because they are formed from the accumulation of sediments over time, which can contain a mixture of different ages of minerals and fossils. Radiometric dating is more commonly used for dating igneous rocks, which are formed from solidified lava or magma, as they contain isotopes that can be accurately measured to determine their age. Therefore, the statement that most sedimentary rocks are readily dated by radiometric methods is false.

When a radioactive isotope decays by electron capture, the electron combines with a proton in the nucleus. This results in the atomic number of the daughter isotope being one less than the parent. This is because the atomic number represents the number of protons in the nucleus, and when an electron combines with a proton, it effectively reduces the number of protons by one. The mass number of the daughter isotope remains the same, as the decay process does not involve any changes in the number of neutrons in the nucleus.

Carbon-14 is actually produced in the Earth's atmosphere when cosmic rays interact with nitrogen atoms. It is not produced by cosmic rays reacting with iron atoms in the Earth's core.

In beta particle emission, a neutron in the parent nucleus is converted into a proton, resulting in an increase in the atomic number by one. However, the mass number remains the same because the mass of a neutron and a proton is approximately the same. Therefore, the correct answer is "The atomic number of the daughter isotope is one more than the parent; the mass numbers are the same."

U-238, Rb-87, and C-14 are all long-lived, radioactive isotopes. U-238 has a half-life of about 4.5 billion years, Rb-87 has a half-life of about 49 billion years, and C-14 has a half-life of about 5730 years. K40, on the other hand, is not a very long-lived isotope. It has a half-life of about 1.25 billion years, which is shorter compared to the other isotopes mentioned. Therefore, K40 is the correct answer as it is not a very long-lived, radioactive isotope.