1st Mid Term

The topmost horizon in most humid region forest soils is the A horizon

False

which of the following soil horizons would likely be found in a densely vegetated redwood forest

O and B horizons

the two soil horizons common in humid, forested areas derived from deep, sandy granitic alluvium are

O and E horizons

organic matter accumulation is most pronounced in the

O horizon

the process by which earthworms, ants move soil up and down in the soil profile is called

Pedoturbation

Eluviation of clay, iron, and other minerals is the principal process responsible for the formation of an E horizon

True

Glacial Till is deposited by melt waters flowing out from the front of glaciers

True

Hydrolysis involves the splitting of water into its H and OH components while hydration attaches intact water molecules to a compound

True

Igneous rocks are formed when molten magma cools and solidifies

True

if you wanted to find a soil where physical weathering dominated over chemical breakdown you would be most apt to find it in

a desert region of Arizona

Soil iron-bearing minerals are chemically reduced by

a permanently high water table at the soil surface

complete oxidation of iron in soils can result in

a red, orange, or brown soil color

If you were to avoid the least favorable location for agriculture, which of the following sites would it be?

a steep colluvial hill slope

Marine sediments are typical parent materials in coastal plain areas

True

Most of the water in our freshwater rivers has come in contact with and has been affected by soils

True

Organic deposits are most common in areas where water flow over the soil surface is restricted and where wetlands form

True

Residual parent materials have formed in a place and have not been transported from one area to another

True

Secondary clay sized minerals are recrystallized products of the chemical breakdown and or alteration of primary minerals

True

The O horizons of a soil are dominantly organic horizons occuring above the mineral horizons

True

The soil A horizons are more apt to be cultivated during agriculture than the E horizons

True

If you were to choose the most favorable location for agriculture which of the following sites would you choose?

an alluvial stream terrace

the presence of rocks such as shale and sandstone indicate the existence of

ancient seas

soils formed on landslide deposits have parent materials which are

colluvial

the mixed angular gravel, rock and soil found at the foot of a slope is typical of what type of parent material

colluvial

Soils highest in a mixture of coarse sand gravel would be formed in _____ parent material

colluvial conglomerate

the loss of soluble salts from soils occurs mainly by

solution weathering and leaching

in the northern hemisphere, soil development is most likely the least on slopes which are

south facing

two landforms upon which one would expect to find alluvium include

stream terraces and floodplains

transformation of gneiss into mica, quartz, and feldspar crystals in an example of

physical weathering and disintegration

Among the following weathering processes which one is most likely to produce iron oxide minerals

reduction and oxidation of augite

climate is a soil-forming factor that results in

regional soil differences

a layer of soil formed by natural processes of soil development is called a

soil horizon

most of the different nutrients essential for growth are supplied to plants directly from the

soil solution

the arragement of primary soil particles into aggregates which are separated by surfaces of weakness is called the

soil structure

which of the following statements is not correct

tropical forests protect the soil from excessive weathering

Soils developed in wind blown parent materials such as loess are generally of poor agriculture value

False

Subsoil is typically equivalent to the O horizon

False

The dark brown and black humus found in many soils does not mix well with clay minerals so there is very little contact between these two soil components

False

Climate influences not only the rate of weathering but the type of native vegetation in an area

True

which of he following horizon sequences would be most characteristic of an "old soil"

(from top down) A, E, Bh, Bt, C

effect of climate soil formation. Select the set of profiles that best shows the effect of climate on soil development as one moves from the east to west across the US

(left side) t, w (right side) O, B, C, E

which of the following essential elements is made available to plants in significant quantities by the weathering of quartz

(none of the above) Si, O, Mg, Ca

which of the following pH values represents the most acidic condition

1.0

the total surface area of a clay soil is about

10,000 times greater than a sandy soil

in the USDA classification system, the size range of sand is

2.0 mm to .005 mm

load of 10 ft.^3 topsoil, how many m.^3 of the volume would be solid material?

5 m^3

in a typical mineral soil in optimal condition for plant growth, approximately what percentage of the pore space would be filled with water and what percentage filled with air?

50% water and 50% air

which of the following pH values represents a neutral condition

7.0

in a given soil, the horizon with the highest organic matter content is generally the ___ horizon

A horizon

topsoil is generally equivalent to which soil horizon?

A horizon

which horizon of a soil profile is most changed from the parent material

A horizon

which of the following soil horizons would likely have the highest percentage of organic matter

A horizon

A soil is developing on a floddplain area of Brizzolara Creek on the Cal Poly campus that is still occasionally flooded. Although the climate is warm here, there is not much rainfall. The vegetative cover is sparse grasses and small forbs. Which of the following is most likely the horizon scenario?

A, C

a soil is developing on the steep south facing slope of Bishop Peak. The native vegetation of this semi-arid location in annual grasses. The parent material is residuum weathered from the underlying igneous rock. Which of the following is the most likely horizon scenario.

A, C

which of the following gases tends to be about ten times more concentrated in the soil atmosphere than in the above-ground atmosphere

CO2

subsoil is generally equivalent to which soil horizon?

B horizon

the last horizon to form as a soil profile develops is the

B horizon (or E horizon if one exists)

in which of the following horizons has the process of illuviation most likely occured

B horizons

which of the soil horizons would more likely be found in a desert than under a rainforest

Bk

hydrolysis

Breaking down complex molecules by the chemical addition of water

silicate clay accumulation is most common in the

C horizon

A soil developed in transported parent materials will likely have properties related to the properties of the bedrock located below the C horizon

False

A, B, C, and E horizons are found in all soils

False

Sandstones are examples of metamorphic rocks

False

An example of chemical weathering of minerals is

Hydrolysis of orthoclase and olivine

shale tends to weather to soils that are

Relatively fertile and fine textured

CHemical weathering is accelerated by water, oxygen, and organic and inorganic acids moving down through decomposed rock

True

most of the water flowing in rivers passed through a soil profile or over soil surfaces before reaching the flowing river waters

True

soil air usually has a higher carbon dioxide content than the air in the atmosphere

True

where in the US would you expect peat deposits to be located

Upper Peninsula Michigan

Agrillic horizons are characterized by

accumulation of silicate clays

the H concentration of a soil solution having a pH of 4 is called

acid

the presence of extrusive igneous rocks indicates the past existence of

active volcanic lava flows

mineral transported by wind from the receding glaciers and deposited on developing soils in the great plains. what type of process is this with regard to the soils developing on the great plains

addition

parent materials transported by water and gravity are called, respectively,

alluvial and colluvial

material deposited by moving fresh water is called

alluvium

the most widely distributed and extensive of all parent materials is

alluvium

transported soil parent materials moved by water and ice, respectively are called

alluvium and glacial

Leoss is a wind deposited soil parent material that originally was

alluvium in large flood plains

a mottled soil condition is caused by

alternating oxidizing and reducing conditions

glacial till is a term used to describe parent materials that

are a heterogenous mixture of mineral debris droppedby receding glaciers

Eolian parent materials are transported

by atmospheric winds from their points of origin

Which of the following conditions would result in the least soil development and weathering assuming that all other soil forming factors are equal

cold dry climate with tundra vegetation

the most common mineral in limestone is

calcite

Examples of Ca-bearing minerals that decompose by carbonation and solution are

calcite and dolomite

which of the following statements is correct

calcium carbonate accumulation is more prominent in arid than in humid regions

the downward leaching of calcium carbonate in soils is accomplished by

carbonation and solution

most chemical weathering processes are promoted by the presence of

carbonic acid

the oxygen found in minerals is

chemically bound to other elements

secondary minerals are most prominent in what fraction of soil

clay

Soils developed from colluvial parent material are usually

coarse, stony, with fast drainage

the water in the soil typically differs from pure water because the soil water

contains organic compounds, contain mineral nutrients, and is restrained in its flow by attraction to particle surfaces

Primary minerals in igneous rocks form during the

cooling and solidification of magma

on a stable upland landscape with little erosion or deposition, one would expect to find

deep residual soils

among the following processes of weathering which one is a physical weathering process

disintegration of feldspars by freezing and thawing

E soil horizons are defined as zones of

eluviation

the downward movement of material (humus, iron oxide, clay) out of the soil surface horizon is called

eluviation

transported soil parent materials moved by wind and ice, respectively are called

eolian and glacial

soils highest in silt would be formed in _____ parent material

eolian loess

functions of soil include:

filtering rain/other water, recycling of organic wastes, supporting bridges/manmade structures, providing habitat for microorganisms that help provide plant nutrients

parent materials derived from weathered basalt results in

fine textured soils containing K, Mg, and Fe

Alluvial soils are most often found on

floodplains and lakeshores

the lower case letter to designate a B horizon with evidence of prolonged periods of water saturation is

g

what mineral is most resistant to weathering under humid temperature conditions

gibbsite

the metamorphic rocks, gneiss and slate, are derived from

granite and shale (respectively)

compared to silt, clay-sized soil particles are characterized by

greater attraction for water

the A horizon of a limestone-derived soil is more acidic than the parent material due to

higher carbonic acid levels

the Bk horizon of a calcareous shale-derived soil has a higher pH than its parent material due to

higher carbonic acid levels in the topsoil

Physical weathering of rock causes

partical size breakdown

Extrusive igneous rocks form under conditions of____than those that exist below the earths surface

higher oxygen levels and lower pressures

the layers of contrasting material found when one digs a hole in a soil are called?

horizons

information about conditions at 2-4 meters deep in a soil is most helpful for understanding

how best to design a building foundation

the reaction : orthoclase + HOH --- K + OH + kaolinite clay is an example of

hydrolosis

among the following processes of weathering which is not physical?

hydrolysis

among the following weathering processes which one is most likely to produce clay-sized minerals

hydrolysis

which set of weathering mechanisms would you expect to be at work in the tropical rain forest of Brazil?

hydrolysis, oxidation, carbonation (formation of carbonic acid) and plant roots

granite is an example of an

igneous rock

Secondary minerals are not found in

igneous rocks and the atmosphere

B horizons are defined as zones of

illuviation

compacting the soil results in which set of changes in percent by volume of its constituents

increase in mineral material and decrease in air filled pored space

increasing the organic matter content of a soil is likely to

increase the soils water holding capacity

granite tends to weather to soils that are

infertile and coarse textured

the element most often involved in oxidation reactions as minerals weather is

iron

sediment deposits in the bottom of fresh water lakes are called

lacustrine

colluvial soils are most often found on

landslides, hill slopes, foot slopes

an eolian deposit of silt-sized materials is called

leoss

soils on south aspects in the Northern Hemisphere generally have _____ than the soils on adjacent north aspects

less vegetative cover and warmer temps

soils developed from accumulated organic material have which of the following characteristics

light porous and productive

eolian parent materials would be mainly located on

loess plains and sand dunes

soil organic matter

makes up approximately 5% of the volume and 1-6% of the weight of a surface soil, and is a major source of N, P and S for plants

Parent materials transported by ocean water and gravity are called respectively

marine and colluvium

residual parent materials are best described as

materials formed by weathering of rocks and minerals in a place

quartz is the last mineral to crystallize from magma as it cools. It is evidence of the rule of thumb that

mineral that form under low pressure and temp are more resistant to weathering

alluvial fans are usually characterized by _____ soils

nearly level

in the Northern Hemisphere, soil development is most likely greatest on slopes that are

north facing

Typically, the older the soil, the greater the

number of different soil horizons

typically the younger the soil, the fewer the

number of different soil horizons

the two common products of hydrolysis weathering of a primary mineral are

nutrients in solution and secondary minerals

soils found on stable mesa summits are usually ____ than soils found on steep hillslopes

older and deeper

as one travels from the northern redwood national park into the California Central Coast, precipitation decreases. One can expect that soil

organic matter content is higher in the forest topsoils

as one travels from the mojave desert into the sierra nevada mountains precipitation increases. One can expect that soil

organic matter content is higher in the mountains

rock exfoliation is caused by changes in

oxidation

in aerobic respiration by microbes, _____ is absorbed and _____ is released

oxygen , carbon dioxide

The unconsolidated and chemically weathered mineral or organic matter from which the solum of the soil is developed by natural processes of development is called

parent material

Metamorphic rocks can best be characterized as

rocks formed by heat and pressure alterations of pre-existing rocks

igneous rocks can be best characterized as

rocks formed when molten magma solidifies

The following is a list of common sedimentary rock types

sandstone, shale, limestone

the most common rock type presently on surface of the land is

sedimentary

the elements added to the soil solution by mineral weathering can be

taken up by plants or leached

the amount of different sizes of mineral particles in a soil defines the soil

texture

the percentages of sand silt and clay in a soil define the soil's

texture

time 0 in soil formation is defined as

the beginning of edaphic conditions

mechanical weathering processes result in

the disintegration of rocks due to different expansion of minerals

physical weathering processes may result in

the disintegration of rocks due to differential expansion of minerals

a soil profile consists of

the set of layers seen in a vertical cross section of a soil

Aspect is a component of which soil forming factor

topography or relief

during the development of a soil from loess parent material, rainwater containing organic acids dissolves carbonates from the loess and moves them down to a zone of accumulation. in order of their occurance, the two processes described are examples are examples of what soil forming processes

transformation / translocation

calcium carbonate in a soil horizon dissolves in the rain water passing through the soil, moves down through the soil profile into the groundwater. This is an example of which soil forming process

translocation (or loss)

igneous, sedimentary, and metamorphic are three

types of rocks

which of the following is not considered one of the five major factors influencing soil formation?

valence state

the presence of basalt indicated the existence of ____ in the past

volcanic activity

Which of the following conditions would result in the greatest soil development, assuming that all other soil forming factors are equal

warm, humid climate

which of the following is true about the hydrolysis reaction

water changes the chemical composition of minerals, making them less resistant to further weathering

the steeper the topography, usually the___ the soil

younger and shallower