chapter 5 learnsmart
calcium ions, silica, bicarbonate ions
Which of the following are products of chemical weathering of Ca-feldspar that are supplied to groundwater?
solution
______________ weathering is a form of chemical weathering where rocks and minerals are dissolved by slightly acidic water
calcite
caves are features that form when flowing groundwater dissolves limestone, which is composed mostly of the mineral...
acids
chemical compounds that give off hydrogen ions when they break down in water
b horizon
clay-rich layer stained red by hematite and limonite
tropical
climate where chemical weathering is most intense
preferential chemical weathering of the ultramafic rocks
diamonds are brought to the surface in kimberlite pipes. the diamonds are widely distributed in the pipe but are concentrated by...
texture
Soil ___________ refers to the proportion of different sized particles, such as sand, silt, and clay
flat or gently sloping uplands where erosion is at a minimum and drainage is good
what is the optimal topography for soil formation?
rills
what is the term used for tiny channels cut into soil by running water?
quartz
what mineral is most resistant to chemical weathering?
regolith
what term do geologists use instead of "soil," which is the common usage term, to refer to the loose, unconsolidated material that covers the earth's surface?
feldspar
when ____________ is exposed to carbonic acid, clay minerals commonly form
paleosol
when a soil is buried and preserved, it can be useful for determining past climates and topography. this type of soil is called...
hardpan
when mineral-rich water deposits sillica and iron compounds in the B layer, a _______ sometimes forms
spheroidal
when rock has been rounded by weathering from an initially blocky shape, the process is called ___________ weathering
parent rock, slope, rainfall, temperature
which of the following are factors that affect the rate of soil formation?
temperature, slope, presence of water, rock type
which of the following are factors that affect weathering?
crop rotation, construction of windbreaks, terracing
which of the following practices can help protect soil from erosion?
ferromagnesians
which of these mineral groups is the most susceptible to oxidation of iron?
subsoil, zone of accumulation
which of these names are also commonly used for the b horizon in soil?
e horizon
pale, sandy layer, leached of clay and elements such as iron and calcium
sheet joints
the parallel fractures shown in this image break the rock into sheets, which can then lead to exfoliation. they are known as _____________ _____________ and they form due to the pressure release
o horizon
uppermost layer; consists entirely of organic material
they are carried away by groundwater or streams
what happens to the soluble products of feldspar weathering?
highly decomposed plant matter found in the O horizon
what is humus
a vertical cross section through soil
what is soil profile?
loam
what is the name for a soil that contains equal amounts of sand, silt, and clay sized particles?
sheet erosion
what is the name for the removal of soil particles by water flowing over the landscape?
e horizon
what is the name of the pale, sandy horizon in the soil profile shown here?
gullies
with continued erosion, rills can deepen into larger channels known as...
clay
a __________ mineral is a hydrous aluminum silicate with a sheet-silicate structure
profile
a soil ___________ describes soil horizons along a vertical cross section through a soil
residual soil
a soil that develops from weathering of the bedrock beneath it is called a...
composed of quartz, feldspar, and clays, sandy in texture, good for plant growth
a soil that develops on weathering granite is likely to be...
pressure release
a type of weathering that occurs when the rocks overlying a body of rock formed at depth are removed, causing the underlying rock to expand and crack
soil
although weathering processes typically work to destroy rock, they also create valuable products such as ____________, which is necessary for agriculture
arid
an alkali soil forms when evaporation of soil water in a ____________ climate leads to heavy buildup of salts that can be toxic to vegetation.
unloading
batholiths form at great depths in the earth's crust. when uplift and erosion remove the overlying rock burden, this is commonly referred to as...
coarse, fine
because they can absorb more rainwater, resulting in less surface runoff and sheet erosion, __________ grained soils erode at a slower rate than __________ grained soils
framework, sheet
feldspars differ structurally from clay minerals in that feldspars are ___________ silicates and clay minerals are ___________ silicates
composition and appearance
how are soil horizons distinguished from one another?
water in the coil freezes and expands, pushing the ground surface upward
how does frost heaving move rocks and soil vertically?
c horizon
incompletely weathered parent material
frost wedging
is the process whereby rock is pried apart by water freezing in cracks and expanding
rock and mineral fragments - anchoring for plant roots clay - attraction of water molecules and nutrients humus - release of weak acids and production of nutrients pore spaces - circulation of air and water
match the components of soil with the roles they play: rock and mineral fragments, clay, humus, pore spaces
aridisols - soils formed in dry climates histosols - wet, organic soils oxisols - heavily weathered verisols - clay-rich
match the following are soil orders with the corresponding descriptions: aridosols, histosols, oxisols, verisols
mechanical
mountain peaks, where there are steep slopes, plentiful precipitation, and freezing and thawing, are sites of the most intense ___________ weathering
chemical weathering on land
much of the dissolved material that makes seawater salty is produced by...
thick, but waterlogged and rich in incompletely decayed inorganic material
on flat bottomlands, soil tends to be...
carbon dioxide
rainwater becomes more acidic as it trickles though soil because soil gas contains ____________, which dissolves in the water, producing carbonic acid
humid, arid
rock chemically weathers much faster in ___________ climates than in ___________ climates
temperature changes, interaction with water, contact with air
rocks exposed on the earth's surface are constantly being changed by environmental factors such as..
sulfuric
strong acid emitted during many volcanic eruptions
frost action
the mechanical effect of freezing water on rocks is known as...
in equilibrium with the physical conditions at the earth's surface
the minerals that form as the products of chemical weathering are...
water
the most important component in weathering, erosion, and transportation is...
carbon dioxide
the most important natural source of acid for chemical weathering is ___________ ___________ dissolved in water
topsoil
the o horizon and a horizon, both rich in organic matter, are often referred to together as...
wind, ice, and water
the primary agents of transportation are...
mechanical weathering increases the surface area exposed to the atmosphere and groundwater
why can mechanical weathering of rock accelerate the rate of chemical weathering of the rock?
gentle rain can infiltrate the soil producing less sheet runoff, gentle rain produces less splash erosion
why does gentle rain over a long period of time produce less soil erosion that heavy rain over a short period of time?
oxygen is abundant in the atmosphere, oxygen is chemically active
why does oxygen combine with minerals or elements within minerals that are exposed at the earth's surface?
carbon dioxide is produced by the decay of organic matter in the soil, organisms in the soil such as worms respire carbon dioxide
why does soil gas contain a higher concentration of carbon dioxide than the atmosphere?
it is extremely abundant
why is carbonic acid the most effective agent of chemical weathering?
arid and semiarid
wind erosion is a particular problem in which types of climate?
substitute easily for cations in minerals changing their composition
acids are effective agents of chemical weathering because the hydrogen ions they give off...
temperate
climate can affect the intensity of mechanical weathering. frost action is most effective in __________ climates, where abundant water repeatedly freezes and thaws
differential weathering
different rock types tend to weather at different rates, with some more resistant than others. this is commonly described as...
rocks subjected to mechanical weathering do not change in composition while rocks undergoing chemical weathering do change in composition, mechanical weathering involves breaking rock apart whereas chemical weathering involves the breakdown of minerals in the rock
identify the ways in which mechanical and chemical weathering can be differentiated from one another?
thin or nonexistent
on steep slopes, where gravity moves material and water downhill and vegetation is thin, soils tend to be...
erosion
once weathering processes break down a rock into loose particles, the particles are removed by the process of...
a horizon
organic material mixed with mineral matter
climate
perhaps the most important factor affecting soil thickness and character is...
salt crystal growth in cracks, burrowing of animals below the surface, extreme changes in temperature, growth of plant roots in cracks
pressure release and frost action are important mechanical weathering processes. which of the following are also mechanical weathering processes?
twelve, horizons
soil is classified into one of __________ orders depending on the characteristics of the __________ in the soil profile
a horizon
the _________ __________ is a dark-colored soil layer that is rich in organic matter and high in biological activity
b horizon
the ___________ ___________ is often clay-rich and stained red or brown by hematite and limonite, which form from iron leached out of the overlying soil by downward percolation water
b horizon
the ____________ _____________ is often clay-rich and stained red or brown by hematite and limonite, which form from iron leached out of the overlying soil by downward percolation water
exfoliation
the process whereby sheets of rock slip off the granite body along the sheet joints is called...
silica, calcite
the products of chemical weathering dissolved in groundwater can precipitate to form cement, which binds loose particles together. what are the two most common cements?
oxidation
the reaction 4Fe+3 + 3O2 -> 2 Fe2O3 is an example of the chemical weathering process known as...
laterites
the thick, red soils that forms from deep chemical weathering in tropical climates are called...
topsoil
the two uppermost, organic-rich, layers
extreme temperature changes
this rock is the mojave desert has been broken apart by...
poor drainage of water
too much clay in soil leads to...
they can contain minerals from a greater variety of parent materials
transported soils are generally made up of a greater variety of constituents than residual soils because __________, making them more fertile
hematite, limonite
which of the following are common oxidation products of iron-bearing minerals?
they tend to be thicker, they have well-developed horizons
which of the following are commonly characteristics of soil that have been weathering for a long period of time?
dissolution of calcite when exposed to slightly acidic rainwater, oxidation of iron bearing minerals that are exposed to the atmosphere, rusting of an iron nail exposed to air, breakdown of feldspar to clay due to exposure to groundwater
which of the following are examples of chemical weathering?
soil characteristics, vegetation, climate, slope
which of the following are factors that affect the rate of soil erosion?
time, slope, climate, living organisms, parent material
which of the following are factors that determine the type of soil that forms?
fertile, thick, well-formed horizons
which of the following are features of soils formed in temperate climates such as in europe and the eastern united states?
supply of dissolved ions to the oceans, concentration of metals such as aluminum, removal of carbon dioxide from the atmosphere, creation of soil
which of the following are positive effects of weathering?
clay minerals, soluble ions
which of the following are products of chemical weathering of feldspar?
soluble ions, silica, iron oxides, clay materials
which of the following are products of chemical weathering of ferromagnesian minerals, such as pyroxene or olivine?
they promote the decomposition of plant material, some bacteria fix nitrogen in the soil making it available for plant uptake
which of the following are reasons why microorganisms such as bacteria, fungi, and protozoa aid soil formation?
iron oxides, quartz, clay
which of the following are solid products of chemical weathering?
decomposition of organic material produces acid which increases chemical weathering of rocks, organisms provide organic material to the soil, plant roots break up underlying bedrock, burrowing animals mix the soil
which of the following are ways in which living organisms play a role in soil formation?
plant roots bind soil particles, leaf canopies protect soil from the impact of raindrops, vegetation can reduce wind velocity
which of the following are ways that vegetation can reduce soil erosion?
wind, raindrop impact, surface-water runoff
which of the following can cause soil erosion?
soil
which of the following is a valuable product of weathering?
calcite
which of the following minerals is completely dissolved by chemical weathering?
c horizon
which portion of the soil profile consists of incompletely weathered parent material and marks the boundary between the developing soil and the underlying unweathered rock or sediment?
b horizon
which soil layer is shown here, marked with a red arrow
mechanical
which type of weathering: cracks in rock are widened due to expansion of water when it freezes to ice
chemical
which type of weathering: minerals exposed to acidic rain or groundwater are completely dissolved
chemical
which type of weathering: oxygen in the atmosphere combines with iron in ferromagnesian minerals to form oxides such as hematite
mechanical
which type of weathering: rock that formed at depth and is exposed at the surface due to unloading undergoes expansion and cracking
the bonds between iron, or magnesium, and oxygen are relatively weak
why are ferromagnesian minerals susceptible to chemical weathering?
rainwater that trickles down through the soil becomes more acidic and attacks the minerals in rock beneath the soil
why is bedrock beneath a layer of soil often found to be chemically weathered?
