Geology Homework 7

slot canyon

A __________ is formed when vertical incision by a stream is the primary process, with relatively minimal mass wasting.

False

The steepest, stable, slope angle possible in unconsolidated, granular materials (e.g., sand and gravel) is called the angle of retention.

rockslide

Which of the following mass movements is most likely to occur in a geologic setting where the rock strata are inclined?

mountain slopes become less steep, nearer the angle of repose valleys become shallower valleys become wide features

Which of the following results from mass wasting? Choose all that apply.

granite

Which of the following rocks would most likely experience sheeting?

A subterranean pluton is exposed at the surface, releasing confining pressure.

Which of the following scenarios best describes how sheeting will develop in an igneous rock?

intense ground shaking during an earthquake

Which of the following scenarios could trigger a mass wasting event? Choose all that apply.

Mudflows deposit talus slopes.

Which of the following statements concerning mudflows is NOT true?

The slide that dammed the Madison River originated from the slopes along the south bank of the river.

Which of the following statements is most strongly supported by your analysis of the landscape around the Madison River placemark?

Erosion and weathering have the same definition and can be used interchangeably.

Which of the following statements regarding weathering and erosion is NOT true?

lahar

Which of the following types of slides is shown in the Slide image layer?

Soils and shallow bedrock were very wet and locally saturated.

Which of the following was a major factor leading to the Gros Ventre, Wyoming, slide?

a sinking building

Which of the following would be physical evidence of permafrost melting?

reactions that occur when rain mixes with carbon dioxide to form carbonic acid

Which one of the following is NOT an example of a mechanical weathering process?

dry sand

Which one of the following materials has the maximum, sustainable, slope angle, as determined by the angle of repose?

solifluction

Which one of the following operates primarily in areas of permafrost?

It involves a major change in the mineral composition of the weathered material.

Which one of the following statements concerning mechanical weathering is NOT true?

E (corner)

Which part of the rock in Figure 2 will get chemically weathered the most quickly?

A block or blocks of unconsolidated regolith slide downhill along a curved slip surface.

Which statement best describes slumping, a mass wasting process?

talus slope

Which term best describes an accumulation of angular rock fragments at the base of a steep, bedrock slope or cliff?

to protect the pipeline against damage due to thawing ground and to keep the crude oil hot and fluid

Why was the Alaskan pipeline built above ground and insulated?

The trunks become tilted in the downhill direction due to creep, but continue to grow toward the sun.

Why would trees be J-shaped?

Mass wasting

________ denotes the downslope movement of soils and regolith.

Scarp

________ denotes the exposed, crescent-shaped rupture surface at the head of a slump.

Gravity

________ is the basic force that moves or accelerates soil and regolith down a slope.

broken retaining wall

A __________ is a common result of creep.

geologic age

All of the following are factors affecting mass wasting EXCEPT for ________.

Mass wasting does not require a transporting medium.

As an erosional process, how is mass wasting unique from wind, water, and ice?

Water expands as it freezes, causing the crack walls to be pushed apart.

Assume that water filling a crack in a rock undergoes cycles of freezing and melting. Which of the following statement is TRUE?

The area of the former reservoir was filled by a series of landslides.

Based on the evidence seen at the Vajont Dam placemark, which of the following statements provides the best explanation for the presence of an unused dam?

Deforestation at the site of the landslide may have contributed to decreased slope stability.

Based on the information gathered in the Landslide image layer, which of the following factors is the most likely contributor to slope failure at this location?

True

Bedding planes and fractures can both act as slip surfaces for rockslides.

True

Calcite, a major component of some monumental and building stones, slowly dissolves in weakly acidic waters.

They were living along rivers and deltas on the edge of an inland sea.

During the late Cretaceous, the Bisti Badlands were home to numerous animals including turtles, crocodiles, and even dinosaurs. What type of environment were they living in?

becomes an earthflow

During wet weather or times when snow is melting, sometimes the downhill toe of a slump ________.

True

Earthflows and slumps generally involve movement of unconsolidated or weakly consolidated soil and regolith.

True

Feldspars commonly decompose during weathering to clay minerals, silica, and soluble constituents.

talus slopes

Frost wedging is the major weathering process contributing to the formation of which regolith material?

just above the highest piece of sandstone seen in the soil

A geologist wants to locate a horizontal coal bed on a soil-covered slope where soil creep is active. A distinctive sandstone bed underlies the coal bed. On the basis of weathered sandstone fragments in the soil, where is the coal bed?

differential weathering

A hoodoo with a cap rock of sandstone and shale below is an example of __________.

True

A scarp is the exposed portion of the rupture surface beneath a slump block.

True

Chemical weathering in bedrock below the land surface often begins along joints and sheeting fractures.

chemical

Clay minerals formed from gabbro or diorite bedrock illustrate which kind of weathering?

one set of widely spaced, sub-horizontal fractures

Consider a steep highway cut made by removing slightly weathered to fresh, fractured, granite bedrock. Which of the following situations is most stable against rockslides?

It will decrease as the slope angle is lessened.

Consider a weathered rock or soil particle lying on a slope. How will the gravitational force pulling the particle downward along the land surface vary with the inclination of the slope?

mass wasting by the gradual downhill movement of sediment, influenced by freeze-thaw or wet-dry cycles

Creep is __________.

The downslope movement of sediment and rock under the direct influence of gravity.

Define mass wasting.

During the freeze, a soil particle moves at a right angle away from the surface, and thawing causes the particle to fall back to a slightly lower level.

Describe how a soil particle moves downhill during the freeze-thaw process.

(From left to right) Triggered by curved oversteepened slopes - Triggered by large amounts of water and steep slopes - Triggered by repeated freezing and thawing of soils on gentle slopes - Triggered by ice wedging or plant activities on steep slopes

Drag the appropriate labels to their respective targets.

(Left) Head scarp (Left) Side scarp (Right) Debris deposit (Left) Rupture surface

Drag the appropriate labels to their respective targets.

Plant roots exert outward pressures as they grow.

How can plants physically weather a rock?

Water expands in volume when freezing, exerting pressure on a container.

How can the creation of ice result in physical weathering?

Water migrated along fractures in the rock, where it froze and wedged the rock apart.

How did weathering destroy New Hampshire's Old Man in the Mountain?

The soil expands and contracts, lifting particles and dropping them a slight distance downslope.

How do freezing, thawing, wetting, and drying contribute to soil creep?

Water lowers the strength and cohesion.

How do the strength and cohesion of clay-rich regolith or soil change with the addition of water?

Physical weathering will fracture a rock, which leaves more area for chemical weathering to attack.

How will physical and/or chemical weathering contribute to create rounded shapes during spheroidal weathering?

the Hawaiian Islands

In what region would climate be expected to have the greatest influence on the rate of weathering?

in moist, temperate climates

In which area would weathering by frost wedging probably be most effective?

steep terrain

In which of the following conditions are rapid mass-wasting processes most likely to occur? Choose all that apply.

True

Lahars are essentially mudflows associated with volcanoes and volcanism.

False

Like most other liquids, water decreases in volume when it freezes.

North

Now that you have oriented yourself, it is time to investigate how the landslide affected the landscape. Using the Gigapan image and Google Earth, determine the general direction in which material was transported during the landslide.

rock avalanche

Of the following, which one would most likely be triggered by an earthquake?

canyons to widen

Over time, mass wasting causes __________.

True

Oxidation of iron is an important chemical weathering process for ferromagnesian silicate minerals like olivine and biotite.

False

Quartz weathers readily to aluminum-rich clay minerals.

A - C - B

Rank the rocks from fastest weathering to slowest weathering.

Peridotite - Gabbro - Diorite - Granite

Rank the rocks from fastest weathering to slowest weathering.

External geologic events such as earthquakes or volcanoes can trigger sudden mass-wasting events. Mass wasting can occur gradually over time or in sudden catastrophes.

Select the two options that are true.

True

Sheeting is mainly a process of mechanical weathering.

False

Slump describes the very slow, downhill movement of soil and regolith.

True

Solifluction is an important mass wasting process in areas of permafrost.

True

Solifluction occurs during the warmer summer months.

South

To break down and understand the Madison Landslide, you first need to orient yourself. Using the Gigapan image and Google Earth, determine which direction (N, S, E, W) you must be facing to see the red star as depicted in the image below.

The ferromagnesian minerals in the gabbro and basalt are subject to oxidation and chemical breakdown.

Under similar warm, moist climatic conditions, why would basalt and gabbro generally have higher chemical weathering rates than rhyolite and granite?

Corners have the most surface area and provide three directions from which chemical weathering can attack.

Using the choice you made for Part C, explain why that part of the rock would chemically weather the most quickly during spheroidal weathering.

D, A, C, B

Using what you know about spheroidal weathering, put the images in Figure 1 in order from the start of spheroidal weathering to the finish.

True

Very fine-grained, iron oxide particles account for nearly all red, yellow, and brown soil colors.

volume increase

What changes are occurring in the igneous pluton that would result in sheeting?

weathering

What is the broad term that refers to the response of Earth materials to a changing environment?

dust-sized grains of iron oxides

What mineral particles are the dominant coloring agents in reddish, brownish, and yellowish soils?

the edges and corners

What portion of an angular, fracture-bounded granitic block shows the highest rate of weathering?

shale

What rock type is the easiest for a river to cut through?

warm temperatures; very moist

What two factors speed up rates of chemical reaction and weathering in rocks and soils?

perpendicular

When sheeting develops in an igneous pluton, fractures will develop in an orientation __________ to the direction of expansion.

sheeting fractures

Which of the following best describes sets of fractures in relatively fresh bedrock, such as granite, which are roughly parallel to the land surface?

cold in the winter, warm in the summer, and with moderate precipitation

Which of the following climates would have the greatest degree of ice wedging?

The Colorado River erodes downward, then mass-wasting processes move material from high to low areas, then the Colorado River transports material downstream.

Which of the following correctly states the role of rivers and mass wasting in the formation of the Grand Canyon?

Earthflows often occur on hillsides in humid areas after times of heavy rain or snowmelt.

Which of the following describes an earthflow?

heat and cold actions of organisms wet and dry freeze and thaw

Which of the following is a process of weathering? Choose all that apply.

slow and subtle movement of material

Which of the following is associated with creep?

limestone caverns

Which of the following is created through the process of chemical weathering?

calcite

Which of the following is/are most susceptible to chemical weathering by dissolution?