Geology 1001 Chapter 9

Uniformitarianism can be stated as __________.

"the present is the key to the past"

Drag events so that they are in the correct order, from oldest at the bottom (6) to youngest at the top (1).

1) deposition of layer one. 2) deposition of later two. 3) deposition of layer three. 4) formation of an unconformity at six. 5) intrusion of granite at five. 6) formation of rocks at four.

Describe the formation of a non-conformity with the first event on top and most recent on the bottom.

A non-layered rock is formed at depth. The nonlayered rock is uplifted to the surface. The nonlayered rock is weathered and eroded. Conditions change, and the eroded surface is buried by sediments. The sediments lithify.

These figures show three types of unconformities. Drag the name for each type of unconformity to the correct figure.

Angular unconformity; Nonconformity; Disconformity

Which of the following statements about James Hutton are correct?

Argued that the time required for geologic processes was much greater than currently perceived. Reasoned that ancient geologic features can be explained by present geologic processes. Considered to be the father of geology. Realized that the layers of sedimentary rock are products of sediment removal and deposition. Worked in Scotland.

The periods of the geologic timescale are named after regions in Europe. For example ___________ is derived from Cambria, and ________ is derived from the Jura Mountains.

Cambrian Jurassic

Trilobites first appeared on Earth during the _________.

Cambrian Period

Archaeology uses this specific isotope to determine the age of bones, wood, and charcoal, preserved at a site.

Carbon-14

In which of the following time periods were mammals the dominant type of life?

Cenozoic

Which is the last step in formation of a typical landscape?

Erosion

Choose the rock types that might exist immediately below a nonconformity.

Granite Nonlayered metamorphic rocks

Which statements are true regarding the geologic timescale.

It was first created using relative dating and correlation. It is based on data from fossils.

Dinosaurs are the best-known creatures of the _____ Era.

Mesozoic

Select the correct eras that are used in the geologic time scale from the choices below.

Mesozoic Paleozoic

The age of Earth is estimated to be 4.55 billion years. This is determined by dating ________.

Meteorites The Moon

Rocks contain evidence that which of the following processes occurred throughout Earth's history?

Mountains were uplifted and eroded. Different types of creatures lived and became extinct. The seas advanced and retreated.

Use the mnemonic to place in order some of the periods of the Paleozoic, Mesozoic, and Cenozoic Eras.

Neogene (most recent) Cretaceous Jurassic Triassic Devonian Cambrian (oldest)

Choose the process that is NOT included in the creation of an disconformity.

Nonlayered rocks are uplifted to the surface.

In which of the following time periods did coral, clams, fish, plants, and insects become abundant?

Paleozoic

Select the correct eras that used in the geologic timescale from the choices below.

Paleozoic & Mesozoic

Match the resulting fossil with its method of preservation.

Petrified wood - Organic matter replaced by silica or pyrite. Insect in amber - Organic matter trapped in tree sap. Dinosaur bones - Hard parts buried and preserved. Fish with fins and scales - Impressions on a lake bed. Fossil fern - Thin films of carbon on a rock surface.

Choose the organism and the process responsible for oxygenating earths atmosphere.

Photosynthesis Cyanobacteria

Match the description of a group of dinosaurs with the correct examples. Had birdlike hip structures and were herbivores.

Stegosaurus and Triceratops.

How did Earth's oxygen-rich atmosphere develop from a carbon dioxide-rich atmosphere?

Through photosynthesis by cyanobacteria.

isotopes that decay slowly are used to date

ancient rocks

Baking of rocks surrounding an igneous intrusion is called _____ effects.

contact

Because all the rock layers in the photograph are horizontal sedimentary rocks, this unconformity is called a _____________.

disconformity

The impressions of fossil shells in this photograph probably indicate that the rock was deposited

in the sea

A _________ fossil is a very short-lived, geographically widespread fossil species known to exist during a specific period of geologic time.

index

The principle of inclusion states that the clasts within a conglomerate are __________ than the conglomerate.

older

The fossil fern in this photograph probably indicates that the rock was deposited

on land

This figure shows the geologic timescale. Drag the label for each period to its correct position on the geologic timescale.

on left: Neogene, Paleogene, Jurassic, Triassic, Permian on right: Cretacious, Pennsylvanian, Mississippian, Devonian, Silurian, Ordovician, Cambrian

Geologists can tell that folded sedimentary rocks have been deformed by the principle of _________ _________.

original horizontality

The oldest known rock found on Earth is dated at _____ years old

over 4 billion

Studies of Archean sedimentary rocks indicate that this gas was absent from Earth's atmosphere for most of the Archean.

oxygen

An impact crater is ____ if it is relatively small, while a(n) ____ crater is larger and has a central peak.

simple; complex

Which fossils provide information as to the mode of formation of an oxygen-rich atmosphere by about 2 billion years ago?

stromatolites

Stratigraphy is the ___________.

study of sequences of rocks, including the rock types, fossils, and inferred environments

The principle of ______________ tells geologists that the oldest rock layer in the diagram is on the bottom; therefore, it was deposited first.

superposition

Of the following numbered units, which is the youngest?

unit 9

In a desert environment, desert _______ and desert __________ can be used to determine the relative age of the land surface because they become more developed with time.

varnish; pavement

isotopes can be used to date _____, which can be found in fractures in granite.

water

What factors are the most critical in determining whether a fossil is preserved?

whether the creature had hard parts and how fast it was buried

The dike is ____ than the rocks it cuts across based on the principle of ____ - ____ relationships.

younger; cross-cutting

Place the isotopes in order, from the system best for dating the youngest materials on the top to the system best for dating oldest materials on the bottom.

Carbon-14 (best for young materials) K-Ar Rb-Sr (best for old materials)

The first humans appeared before 3000,000 years ago in the ____ Era.

Cenozoic

Order the four chapters in Earth history from youngest at the top to oldest the bottom.

Cenozoic Mesozoic Paleozoic Precambrian

Match each geologic era with its meaning in the fossil record.

Cenozoic - Recent life. Mesozoic - Middle life. Paleozoic - Ancient life.

Which materials can be dated with carbon-14 technology at archeology sites?

Charcoal Bones Wood

Evidence for the cause of the dinosaurs' extinction at the end of the Mesozoic era can be found at _______.

Chicxulub crater, Mexico Deccan Traps, India

Which of the principles of relative dating would be useful in determining the age of the orange granite?

Contact effects Cross-cutting relations

What defines the boundaries between each of the three eras in the geologic timescale?

two great mass extinctions

Buried erosion surfaces that represent large intervals of time are called ____________.

uncomformities

Isotopes are different forms of an element that have different _____ (check all that apply)

Number of neutrons Atomic Weights

If a rock started with 1,000 atoms of a parent but now contains 250 atoms, how many half lives have passed?

2 half lives

The geologic contact observed by James Hutton at Siccar Point is now called a(n) _____ by geologists because it represents an ancient erosion surface.

unconformity

Match the age-dating term on the left with its correct definition on the right.

Relative dating Uses geologic principles and common sense. Isotopic dating Uses analytical methods and assigns numbers.

Isotopic dating is accomplished by assigning ages in years to rocks using __________ dating methods.

analytical

The sedimentary rocks numbered 4 to 7 can be ordered using the principle of ___________.

superposition

Drag the figures so that they are in the correct order, arranged from oldest at the top (1) to youngest at the bottom (5). Move your cursor over position in the right column to get hints about that event.

1) deposition of a lower tan layer. 2) deposition of a middle grade layer in swampy environments. 3) deposition of the uppermost layer. 4) a time of no deposition and formation of a river. 5) erosion of a canyon.

Place the isotopic systems in order, from the system best for dating the youngest materials on the top to the system best dating hte oldest materials on the bottom.

1. Carbon-14 (best at dating youngest materials) 2. K-Ar 3. Rb-Sr (best at dating oldest materials)

Before radioactive decay occurs, there exist 200 parent atoms. After one half-life, there would be _____ parent atoms and _____ daughter atoms.

100 100

Match the isotopic system elements that could be used for dating with the correct geologic example.

Carbon-14 Charcoal incorporated into recent sediment. K-Ar A volcanic eruption. U-Pb A solidification of a granite.

Which principle of relative can be used to determine when the minerals associated with the granite intrusion in the diagram formed?

Cross-cutting relations

Which principle can be used to determine the relative age of an igneous intrusion called a dike?

Cross-cutting relations.

Indicate the typical sequence of formation for sedimentary rock landscapes, beginning with the first even at the top and the last event at the bottom.

Deposition of sediments in layers (first) Lithification into sedimentary rocks Erosion of rocks into a landscape

Determine the sequence of events that created the rocks shown by putting the following in order, with the oldest (and first) event on the bottom and the most recent event on the top.

Deposition of tan fossil-bearing layer. Land surface eroded, forming igneous pebbles. Cross-cutting dike intruded. Green shale and gray limestone deposited horizontally.

Observed changes (evolution)

Development of stronger front fins in Paleozoic fish occurred, as compared to fish fossils found in older rock layers.

Match the time period within the Paleozoic Era with examples of the forms of life that existed on Earth.

Early Paleozoic An explosion of life with hard parts occurred. Middle Paleozoic Fish became abundant and diverse in the ocean. Late Paleozoic Amphibians and reptiles evolved on land.

Match the geologic term related to lateral changes in rock type with its meaning in the list shown

Facies change Different sediments are desposited due to a change in the environment. Erosion Missing rocks are marked by an unconformity. Restricted event A deposit is of limited aerial extent. Change in thickness River deposits become thinner at the edge of a valley.

True/False: A disconformity occurs above tilted rock layers.

False; an angular unconformity occurs above tilted rock layers.

Evolutionary theory

Favorable genetic mutations occurring in a species are more successful in small, isolated populations than in large populations.

The principle of faunal succession states that ____.

Fossils species change upward from older layers of sedimentary rock to younger layers. Fossil species show a systematic change with time.

What geologic features could cut across sedimentary rocks and therefore than the rocks they cut across?

Fractures Dikes Veins

The discovery of ____ allowed geologists do use isotopes to finally determine the age of Earth with accuracy.

Radioactivity

Identify possible causes of the great dying, the great extinction at the end of the Paleozoic.

Large meteorite impact Outpouring of lava Formation of the supercontinent Pangea

Geologic events occurred to trap oil and gas in an anticline.

Layers of sedimentary rocks are deposited horizontally. (first event) Rocks are folded into an anticline. Oil and gas are trapped by the fold. (last event)

Which unconformity is produced when an eroded surface of an igneous or metamorphic rock is buried by layers of sandstone and conglomerate?

Nonconformity

To what does the term evolution refer?

Observed changes in the fossil record; One or more theories that help explain observed changes; As a general term to describe how something, such as a landscape, has changed over time. **All of these choices are correct.**

How does an angular unconformity form?

Older rocks are tilted, eroded, and overlain by younger rocks.

Which principle of relative dating can be used at Siccar Point in Scotland to determine that the rocks below the unconformity were tilted to vertical before erosion occurred?

Original horizontality

Which are principles of relative dating?

Original horizontality Cross-cutting relations Superposition

The oldest rocks and minerals on Earth's surface have been found in Canada, Greenland, and Australia and are from the _________.

Precambrian

Which chapter of geologic history is the earliest and represents 90% of geologic time?

Precambrian

Which of the following is the earliest (oldest) chapter of geologic time?

Precambrian

Which events occurred at the beginning of the Cambrian Period, approximately 542 million years ago? (Select all that apply.)

Rapid evolutionary change Explosion in the amount of diversity of life Evolution of more organisms with hard parts

Order the events that form an angular conformity from the first event at the top to the last event at the bottom.

Rocks are deposited horizontally. Rocks are folded. Uplift occurs, and folded rocks are eroded. Horizontal rocks are deposited over eroded tilt beds.

Place the events that formed the landscape shown in the correct sequence, from the first event at the top to the last event at the bottom.

Sedimentary layers are deposited horizontally. Sedimentary layers are lithified. The river cuts through the rock layers. The canyons widen and tributaries form.

Describe the formation of a disconformity with the first event on top and the most recent event on the bottom.

Sedimentary rocks are formed in horizontal layers. The rocks are exposed at the surface. Weathering and erosion occurs. Younger sedimentary rocks are deposited in horizontal layers.

Which principle is used to determine the age of rocks by ordering them from oldest on the bottom to the youngest on the top?

superposition

Match the principle of relative dating with its definition.

Superposition - The oldest rock is at the bottom. Cross-cutting relations - The fault is younger than the rocks is cuts across. Original horizontality - Sediments and volcanic units are usually deposited in flat-lying layers. Inclusions - Rocks may incorporate older pieces of rock. Contact effects - A baked zone forms next to a dike during intrusion.

Which of the following is NOT a way in which fossils can be preserved?

They can be replaced by hard materials, such as silica; They can be buried and decay, leaving a cavity in the rock; They can be preserved in ancient tree sap; They can be too small to see but can build diagnostic features in the rocks. **All of these are ways a fossil can be preserved.**

Which of the following types of data could be used by geologists to estimate the age of past Earth events?

Tree rings Ice cores Lake varves

_____ may form as erosion by a river further downcuts and widens a canyon, making a more intricate canyon formation.

Tributaries

An igneous dike will bake the surrounding rock, indicating that the dike is older than the surrounding rock.

True

This photograph shows an upper unit with fragments and a lower unit with tilted layers. Which of the following statements is true?

The upper unit is younger because it is on top; The upper unit is younger because it contains pieces of the underlying unit; The lower unit is older because it was tilted and eroded before deposition of the upper unit. **All of these choices are correct.**

Which are important about fossils in the rock record?

They are evidence of ancient life. They document evolution of life. They can be used to date rocks.

True of False: Scientists use various techniques to date the age of the Earth before the discovery of radioactivity.

True

You can use both superposition and contact effects to determine that the light-colored volcanic rock is younger than the underlying unit.

True

Match the description of a group of dinosaurs with the correct examples. Diverse group of carnivores and herbivores with hip structures similar to lizards.

Tyrannosaurus rex and Apatosaurus.

What type of feature is represented by the boundary between geologic units 2 and 3?

Unconformity

Match the type of geologic hazard with the method that can be used to date when it last occurred.

Volcanic eruptions Using isotopic methods, such as Ar-Ar dating. Earthquakes Using cross-cutting relations to determine the age of the fault. Flooding Using the amount of soil development and carbon-14 dating on terraces.

Which of following geologic events is the youngest? (picture in 9.14 of textbook)

accumulation of the oil and gas

Where are the oldest rocks in the column of sedimentary rocks normally found?

at the bottom

Early Earth would have been inhospitable to many life-forms today because the _____________.

atmosphere lacked oxygen

The discovery of radioactivity in the early 1900s allowed geologists to determine the age of Earth to be approximately 4.6 _____ years.

billion

An unconformity is a(n) ____.

buried erosion surface that is preserved beneath later deposits

When a geologist attempts to match up two different sections of rock according to time, he or she is __________ the rocks.

correlating

Geologists match rock units using rock types, isotopic ages, and fossils. This type of geologic matching is know as ___________.

correlation

In geology, determining time equivalency in rocks is called ________.

correlation

The mineralized granite intrusion shown can be dated by its relative age using the principle of _____-_____ relations

cross, cutting

When an igneous dike cuts across sedimentary strata, the principle of __________ relations can be used to determine the relative age.

cross-cutting

Which principle of relative age dating can be used to determine when the river formed on the landscape?

cross-cutting relations

About 2 billion years ago, ____ had produced enough oxygen through photosynthesis to form a protective layer of ozone in the atmosphere.

cyanobacteria

Which of the following features look like fossils but are not?

dark minerals that grow in branching patterns

James Hutton inferred that the rocks below the contact at Siccar Point were vertical gray sandstone and shale and the rocks above were gently dipping red sandstone and conglomerate. Therefore, the histories of these rocks were ____.

different

Fossils change through a section of rocks because ____.

different species were alive during different periods of time

The term half life represents the time it takes

for half of the parent atoms to decay into daughter atoms.

If a creature has hard parts and is rapidly buried after death, it is more likely to become a(n)

fossil

If has hard parts and is rapidly buried after death it is more likely to become a _____

fossil

This figure has rock units and geologic features that are assigned letters that are not in any particular order. From the geologic relations, what is the oldest unit?

granite (unit G)

Groundwater can be dated using _________.

isotopes

Dating using radioactive isotopes that decay over time is called ________ dating.

isotopic

When geologists assign actual numbers to the age of rock unit, they determine the ____ age.

isotopic

Finding several species of fossils, rather than just one, in the same rock layer is more useful to geologists because

it indicates the sediments must have been deposited at the same time when all the species were present

Unit C is present in the left column but not the right column because

it was not deposited or was eroded away.

The Cenozoic Era is called the age of __________ because of their abundance and diversity during this time.

mammals

Fossils of species that lived on Earth for a long time period are often found in _________, whereas fossils of species that lived for a shorter time are often found _________.

many rock layers; in a layer or two

The instrument that is used to measure the ratios of parent to daughter products in a rock or mineral is called a _______.

mass spectrometer

When several species of fossils are found in adjacent layers, the time of formation of each rock layer can be assigned to a ____________ span of time.

narrow

An isotope refers to any element that has the same number of protons but a different number of ________.

neutrons

River terraces are _____ than the age of the modern river channel.

older

The tree eras of the geologic timesale are divided into units called _____

periods

A hypothesis that explains how new organisms or new characteristics can appear suddenly in the fossil record is called

punctuated equilibrium

Isotopic dating allows scientists to assign numeric ages to rock using the natural ___ decay to certain isotopes.

radioactive

Both _________ dating and ______ dating can be used for correlation of the rock units shown in the diagram.

relative isotopic

Rocks around the world contain evidence that ____ have advanced and retreated, and ____ have been uplifted and eroded.

seas; mountains

Organisms with soft body parts only are rarely preserved as fossils; they may leave behind indirect evidence of their existence as _____ fossils.

trace

Preserved trackways and worm burrows in rock are examples of __________.

trace fossils

True/False: Cross-cutting relations can be used to determine that the Colorado River cut through the Grand Canyon after sedimentary rocks formed.

true