Historical Geology Exam Review

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The record of Earth’s past is primarily made up of __.

rocks.

The principle stating that geological processes observed today have also happened in the past is called __.

Uniformitarianism.

In an undisturbed sequence of rock layers, the __ rock layer is at the bottom and the younger layers are above.

oldest.

Relative dating places __ in chronological order without providing an exact age.

rock layers.

The principle that states layers are generally deposited in a __ position is known as the Principle of Original Horizontality.

horizontal.

When faults cut through rock layers, the fault is __ than the rock it cuts through.

younger.

Geologists use __ fossils to correlate the age of rock layers.

index.

An unconformity where rock layers vanish due to erosion is called a __.

disconformity.

Petrified remains are organisms that __.

turn to stone.

Molds reflect the shape and surface markings of an organism, while __ are created in the hollow spaces of a mold.

casts.

Fossils that provide indirect evidence of prehistoric life, like footprints, are called __ fossils.

trace.

The Geologic Time Scale breaks Earth's history into units based on the __ record.

rock.

The __ Era was known as the age of reptiles and saw the rise of dinosaurs.

Mesozoic.

The __ Era, which began 65 million years ago, is referred to as the age of mammals.

Cenozoic.

The process of determining the absolute age of rocks is referred to as __ dating.

absolute.

The unstable parent isotopes decay into stable __ isotopes.

daughter.

The __ is the amount of time required for half of the nuclei in a sample to decay.

half-life.

Fossils that help correlate rock layers must be widespread, abundant, and live for a __ time.

short.

A layer of sediment preserved in an unchanged manner, such as a mammoth in permafrost, is an example of __ remains.

preserved.

The __ unconformity occurs when layers of sedimentary rock form over tilted older rocks.

angular.

Radiometric dating is a technique used to date materials by comparing the abundance of a radioactive isotope to its _ products.

decay

The process of using radiometric dating to determine the age of a sample requires measuring the concentration of _ isotope and its _ products.

radioactive, decay

What is the maximum age limit for reliable Carbon-14 dating?

The maximum age limit for reliable Carbon-14 dating is about 50,000 years.

In radiometric dating, a sample's age can be calculated by knowing the amount of _ isotope present.

parent

What is the significance of a mineral's closure temperature in radiometric dating?

Closure temperature is the temperature below which isotopes are no longer free to move, marking the start of radioactive decay.

The ratio of parent isotopes to daughter isotopes in a sample is crucial for determining its _ using radiometric dating.

age

What does the term 'radiocarbon dating' specifically refer to?

Radiocarbon dating refers to the method of dating organic materials using Carbon-14 isotopes.

As they decay, radioactive isotopes produce stable _ isotopes over time.

daughter

The reliability of radiometric dating increases with the _ of the sample and the type of isotope used.

age

What can cause discrepancies in radiometric dating results?

Contamination, isotopic fractionation, and incorrect initial conditions can cause discrepancies.

The age of the Earth is estimated to be approximately _ billion years based on radiometric dating techniques.

4.5

Fossils are preserved remains or signs of _ that lived in the past.

organisms

The Law of Superposition states that in undisturbed sedimentary rock layers, the _ layers are at the bottom and the _ layers are at the top.

oldest, youngest

_ is the principle that geological processes happening today have also occurred in the past.

Uniformitarianism

Fossils help in relative dating by allowing scientists to identify the _ of rock layers based on the fossils they contain.

relative ages

_ fossils are used as indicators of specific time periods for comparing the ages of rock layers.

Index

Relative dating determines the sequence of events and the _ ages of rock layers without giving exact dates.

relative

The principle of _ states that layers of sediment are initially deposited horizontally due to gravity.

original horizontality

Fossil occurrence is important in understanding Earth's history because it shows the evolution of _ and ancient environments.

life

An _ is a gap in the geological record caused by erosion or the lack of deposition of sediment.

unconformity