Geology exam 3-- part 1

Compaction is a very important part of the lithification process for which of the following sediments?

mud

Which of the following sedimentary features would typically be found in shales but not in sandstones?

mud cracks

What is the main difference between a conglomerate and a sedimentary breccia?

Breccia clasts are angular; conglomerate clasts are rounded.

What is the chemical formula for dolomite, the major mineral in dolostones?

CaMg(CO3)2

Which of the following describes the correct order for relative solubility of minerals in sedimentary rocks?

Evaporate minerals are more soluble than calcite and quartz.

Which of the following locations is a likely place to find a braided stream?

Flowing from the terminus of a glacier

Which of the following scenarios represents the best nonstructural approach to flood control?

Managing a floodplain to limit development in sensitive areas

What will happen to the water level in the stream if the water table is below the level of the stream channel?

The stream will lose water to the groundwater system.

Which statement concerning sedimentary rocks is not true?

They were originally deposited at depth below the bottom of the sea.

________, a common mineral found in igneous rocks, is the most abundant mineral in detrital sedimentary rocks.

quartz

Flint, chert, and jasper are microcrystalline forms of ________.

quartz (SiO2)

What are the chief constituents of detrital sedimentary rocks?

quartz and clay

How will channel velocity change along the longitudinal profile of a stream?

Velocity will start low and gradually increase toward the mouth due to increasing discharge downstream

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

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

Which of the following regions would you expect to exhibit the highest rates of weathering?

a tropical rainforest

Which part of a stream's sediment load moves the slowest?

bed load

A ________ stream consists of a complex network of converging and diverging channels that weave around channel bars.

braided stream

Which detrital sedimentary rock is made up of gravel-sized, angular fragments?

breccia

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

calcite

Detrital grains of which mineral(s) are extremely rare in detrital sediments? Why?

calcite; it is soft and relatively soluble

What material is coal primarily made of?

carbon

Which type of limestone consists mainly of tiny, marine fossils composed of calcite?

chalk

Clay minerals, silica (SiO2), and dissolved potassium bicarbonate in the soil water are products of which process?

chemical weathering of orthoclase feldspar

Which of the following factors has the greatest influence on soil formation?

climate

Studies of deep-sea sediment cores have contributed greatly to scientific knowledge of ________.

climatic changes during the last four million years

Which of the following sedimentary rocks would you expect to have originally been deposited by fast-moving streams?

conglormate

A lake is found in which type of sedimentary environment?

continental

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

in moist; temperate climates

Which of the following would retain the most detailed impressions of fossilized organisms?

very fine-grained volcanic ash deposited in an ancient lake

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

warm temperatures; very moist

What is infiltration?

water soaking into the ground

What are the three main zones of a river system from highest to lowest?

zone of sediment production, zone of transportation, and zone of deposition

What is the geologic definition of a stream?

A channelized body of water flowing down gradient

Why are urban areas susceptible to flash floods?

A high percentage of the surface area is covered with cement, asphalt, and other impervious materials

What is the longitudinal profile?

The cross-sectional area from the headwaters to the mouth

What is base level?

The downward limit of erosion.

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

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

What is a stream's longitudinal profile?

a cross-sectional view of a stream from the headwaters to its mouth

Which of the following is not a type of limestone?

arkose

________ sandstone contains abundant feldspar, suggesting that the sand was derived by weathering and erosion of granitic bedrock.

arkosic

According to the hydrologic cycle, once precipitation has fallen on land, what paths might the water directly take?

evaporation/transpiration runoff into a river infiltration into the ground runoff into the sea

As stream velocity slows, the smallest particles get deposited first.

false

Boulder conglomerates suggest deposition by strong winds in a desert.

false

Chalk, coquina, and ancient coral reefs are primarily composed of microcrystalline quartz.

false

Clastic particles in a sedimentary breccia are rounded and are about the same size as fine-grained sand.

false

Ferromagnesian minerals (like olivine and pyroxene) that crystallize at high temperatures in Bowen's reaction series are generally much less susceptible to chemical weathering than quartz.

false

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

false

Mud cracks in a shale or mudstone indicate that the mud or clay was deposited in deep waters of an offshore marine environment.

false

Point bars are locations where erosion occurs whereas cutbanks are locations where deposition occurs.

false

Quartz weathers readily to aluminum-rich clay minerals.

false

The chemical sedimentary rock, conglomerate, is composed of gravel-size, rounded, calcite oolites.

false

________ are flat areas along streams that are created by the deposition of alluvium and is subject to periodic inundation.

floodplains

During what periods would streams see the greatest erosion and transportation of sediment?

floods

________ is not a common cementing agent for sandstones.

fluorite

Coal beds originate in ________.

freshwater coastal swamps and bogs

What mechanical weathering process produces talus slopes?

frost wedging

Which one of the following is an important, mechanical weathering process for enlarging fractures and extending them deeper into large boulders and bedrock?

frost wedging

In which part of a stream's course would one typically find bedrock channels?

headwaters

Which characteristic is absolutely necessary for a sedimentary rock to have potential as a possible reservoir rock for oil or gas?

high porosity

Which of the following minerals would break down most quickly in a chemical weathering process?

hornblende

The ________ describes the path water takes as it moves between the land, the ocean, and the atmosphere.

hydrologic cycle

What two chemical constituents cannot form by chemical weathering of the feldspar minerals?

insoluble iron oxides and soluble magnesium bicarbonates

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

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

Potassium feldspar chemically weathers to produce _____ in great quantities.

kaolinite

Nonclastic textures are common in which of the following sedimentary rocks?

limestones

According to scientists and engineers, which of the following is the best type of flood control?

limiting the amount of development within a flood plain

Which of the following beds would be easiest for a stream to erode?

lined with silt

Which type of sediment undergoes the most compaction as it lithifies to sedimentary rocks?

marine mud

Which term best describes those processes that move weathered rock materials and soils downslope?

mass wasting

Physical breakdown of rock into smaller pieces is called ______.

mechanical weathering

Where is the zone of sediment production in a stream?

near the headwaters

When does the deposition of solid particles occur?

only when the fluid transporting the sediments slows down or when glacial ice melts

What is the main criterion for classifying detrital sedimentary rocks?

particle size

What type of drainage pattern develops on highly jointed bedrock?

rectangular

Would you call the loose, unconsolidated, surface material on Mars regolith or soil?

regolith

Which term describes a soil formed by weathering of the underlying bedrock?

residual

Which of the following sedimentary features can each be used to determine paleocurrent directions?

ripple marks and cross stratification

What is the ultimate base level?

sea level

Which one of the following is not a chemical sedimentary rock or evaporite?

shale

Oolitic limestone is most likely to form in what type of depositional environment?

shallow, clear, marine waters with vigorous current activity

A cherty limestone would contain which major constituents?

silica; calcite

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

talus slope

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

talus slopes

Transpiration moves water from _______.

the biosphere to the atmosphere

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

the edges and corners

Which one of the following statements best describes erosion?

the process by which weathered rock and mineral particles are removed from one area and transported elsewhere

Which of the choices below is not a factor that causes infiltration and runoff to vary from place to place and from time to time?

time of the day

Which of the following applies to the basic constituents of halite, gypsum, and sylvite?

transported as dissolved ions; deposited by evaporation

A feldspar-rich sandstone is called an arkose.

true

Abundant moisture and warm temperatures result in high rates of chemical weathering.

true

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

true

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

true

Clay and muddy sediments lithify to form shales and mudstones.

true

Decomposition of pyrite is an important factor in generating acidic mine drainage.

true

Detrital sedimentary rocks are classified according to clastic particle size; chemical sedimentary rocks are named according to the most abundant minerals.

true

Detrital sedimentary rocks have clastic textures.

true

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

true

Many limestones are of biochemical origin.

true

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

true

Peat is thought to be the original material from which coals are formed.

true

Quartz is quite resistant to weathering and is an important component of sands in riverbeds and on beaches.

true

Sheeting fractures and exfoliation domes commonly develop in areas with highly fractured bedrock.

true

Sheeting is mainly a process of mechanical weathering.

true

The Nile River in Africa is a stream.

true

The mineral dolomite, which is the major mineral of the sedimentary rock dolostone, is a carbonate of calcium and magnesium.

true

Water is gradually expelled from compacting clay and mud sediments.

true

Which of the following best describes bedded gypsum and halite?

vaporates; chemical, sedimentary rocks