Chapter 9

Describe the formation of a nonconformity by putting the following in the correct order, with the first event on top and the most recent on the bottom.

- A nonlayered 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.

Different analytical dating methods can be used on the same rock. What types of information can be learned about a rock's history using these methods?

- Age when magma solidified & - How fast an igneous rock cooled through time.

The periods of the geologic timescale are named after regions in Europe. For example:

- Cambrian is derived from Cambria, & - Jurassic is derived from the Jura Mountains.

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

- Carbon-14 - K-Ar - Rb-Sr

Which of the following geologic features look like fossils but aren't because they form through inorganic processes?

- Dendrites & - Concretions.

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.

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

- Desert varnish & - Desert pavement

What geologic features cold cut across sedimentary rocks and therefore are younger than the rocks they cut across?

- Fractures. - Dikes. - Veins.

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

- Granite & - Nonlayered metamorphic rocks.

Why is burial necessary for fossil preservation?

- It doesn't allow the organism's remains to decompose or be scavenged.

Identify possible causes of the Great Dying, the mass extinction at the end of the Paleozoic.

- Large meteorite impact. - Outpouring of lava. - Formation of the supercontinent Pangeaea. - Major changes to ocean structure.

What events occurred at the beginning of the Cambrian Period, approx 542M years ago?

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

Which two dating can be used for correlation of the rock units shown in the diagram.

- Relative dating & - Isotopic dating

Order the events that form an angular unconformity 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.

Which statements explain why the rocks of the Grand Canyon do not represent all of geological time?

- Rocks from the first 2.8 billion years of Earth history are missing. - Unconformities record missing time.

Describe the formation of a disconformity by putting the following in the correct order, 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.

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

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

What does relative dating do to determine the order in which geological events occured?

- Uses common sense -Uses geological principles

Which of the following statements about James Hutton are correct?

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

Isotopes are different forms of an element that have different:

- atomic weights & - numbers of neutrons

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

- cross-cutting relations. - contact effects

Which of the following statements are true regarding the geologic timescale?

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

The oldest rocks in the Grand Canyon are:

- metamorphic, - plutonic, & - Precambrian.

The age of the Earth is estimated to be 4.55 B years. This is determined by dating:

- meteorites & - the Moon

The Grand Canyon exposes all 3 types of unconformities:

- the disconformity, - nonconformity, & the - angular unconformity.

Which of the following are important about fossils in the rock record?

- they document the evolution of life. - they are evidence of ancient life. - they can be used to date rocks.

Examine the image. Which numbered rock layer is the youngest?

1 lol

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

1. Deposition of sediments in layers. 2. Lithification into sedimentary rocks. 3. Erosion of rocks into a landscape.

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

1. Sedimentary layers are deposited horizontally. 2. Sedimentary layers are lithified. 3. The river cuts through the rock layers. 4. The canyons widen and tributaries form.

What is an uncomformity?

A buried erosion surface that's preserved beneath later deposits.

Because of their abundance and diversity during this time, what is the Cenozoic Era called?

Age of Mammals

The first organisms on Earth included:

Algae.

Isotopic dating is accomplished by assigning ages in years to rocks using what dating methods?

Analytical Dating Methods

Isotopic dating means that ages are assigned to rocks using what methods?

Analytical Methods.

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

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

Baking of rocks surrounding an igneous intrusion is called what?

Contact effects - Younger rocks can cause changes along their contacts with older rocks, providing information on relative ages.

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

Cross-cutting relations. - Principle 4 states that younger rocks or features can cut across any older rock or feature.

The dike is younger than the rocks it cuts across based on the principle of:

Cross-cutting relationships.

About 2B years ago, what had produced enough oxygen through photosynthesis to form a protective layer of ozone in the atmosphere?

Cyanobacteria

Evidence for the cause of dinosaurs' extinction at the end of the Mesozoic Era can be found at:

Decccan Traps, India. -The Deccan Traps resulted from a massive outpouring of basaltic lava that would have choked the atmosphere with sulfur dioxide. Chucxulub crater, Mexico - This crater is the impact site of a massive comet or asteroid.

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 Had birdlike hip structures and were herbivores. - Stegosaurus and Triceratops

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

Early Paleozoic. - Sea life such as corals, crinoids, mollusks, trilobites, and snails were abundant. Middle Paleozoic. - Fish became diverse and abundant 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.

T or F: A disconformity occurs above tilted rock layers.

False - An angular unconformity forms above tilted layers.

What type of fossil is short-lived, geographically widespread fossil species known to exist during a specific period of geologic time?

Index Fossil

A jellyfish is unlikely to become a fossil because:

It lacks hard parts.

The instrument that's used to measure the ratios of parent to daughter products in a rock or mineral is called a:

Mass spectrometer.

Which Era is known as the age of dinosaurs, after the best-known creatures of this age?

Mesozoic Era.

Use the mnemonic Cuddly Old Sheep Dogs Make Perfect Pets; They Just Crowd People Nearby Quiet Places to place in order some of the periods of the Paleozoic, Mesozoic, and Cenozoic Eras. Put the oldest period at the bottom and the most recent period at the top.

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

Isotopic dating of basement rocks in ___________ suggest Earth has a long history because the oldest rocks, from the area of the Canadian Shield, are more than 3B years old.

North America.

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.

The sedimentary rocks in the Grand Canyon that record the coming and going of the sea, as well as rivers and deserts, were deposited in what era?

Paleozoic Era

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 or preserved. Fish with fins and scales - impressions on lake bed Fossil fern - thin films of carbon on a rock surface

What dating is concerned with the order in which geological units were formed, rather than with their age?

Relative dating

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

Stratigraphy.

Match the principle of relative dating with its definition.

Superposition - the oldest rock is on the bottom. Cross-cutting relations - the fault is younger than the rocks it cuts across. Original horizontally - sediments and volcanic units are usually deposited in flat-laying layers. Inclusions - rocks may incorporate older pieces of rock. Contact effects - a baked zone forms next to a dike during intrusion

The end of the Paleozoic Era, marked by the extinction of about 70% of land species, is known as:

The Great Dying

What is subdivided into 3 eras since the end of the Precambrian?

The geological timescale

What principle tells geologists that the oldest rock layer int he diagram is on the bottom; therefore, it was deposited first.

The principle of superposition.

Preserved trackways and worm burrows in rock are examples of what?

Trace fossils.

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

Tributaries.

T or F: Scientists used various techniques to date the age of the Earth before the discovery of radioactivity.

True. - They did try with the technology available.

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

Two great mass extinctions.

"The present is the key to the past" is a phrase commonly used to summarize the geological concept of what?

Uniformitarianism

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

correlating

The principle of original horizontality means that flat-lying sedimentary rocks haven't been:

deformed

James Hutton inferred that the rocks below the contact at Siccar Points 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

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

Ancient rocks must be dated with isotopes with a ________ half-life

long

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

many rock layers; in a layer or two.

How old is the oldest known rock found on Earth?

nearly 4B years old.

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

older

William Smith established the principle of _________ succession from the information he gathered while surveying rocks along canals in England, Wales, and Scotland. There he collected fossils and noted which fossils were common in which layers?

the Principle of faunal succession. - The geologic map of England, Wales, and Scotland that William Smith created is infamous.

Early scientific attempts at determining Earth's age gave a number that was:

too young

The oldest ice cores in Antarctica have over _________ annual layers.

100k

Using radioactive decay to date a rock, a scientist finds that only 25% of the original isotope is remaining. How many half-lives have passed?

2

The discovery of radioactivity in the early 1900s allowed geologists to determine the age of Earth to be approx:

4.55 B years.