WorksheetsWeathering and Soil Formation: Rocks and Petrology
Total questions: 117
Worksheet time: 59mins
What does petrology primarily study?
The movement of tectonic plates
The study of rocks concerned with composition, structure, and origin
The atmosphere’s layers and weather patterns
The chemistry of ocean water
Which statement best distinguishes intrusive from extrusive igneous rocks based on cooling history?
Intrusive rocks cool fast at the surface; extrusive rocks cool slowly underground
Both intrusive and extrusive rocks cool at the same rate but in different seasons
Intrusive rocks cool slowly from trapped magma; extrusive rocks cool rapidly from lava
Extrusive rocks do not solidify from molten material
Which texture correctly matches an igneous rock description?
Phaneritic: fine-textured due to lack of crystal growth
Aphanitic: coarse-textured with large visible crystals
Porphyritic: larger crystals (phenocrysts) surrounded by a finer groundmass
Vitreous: coarse-textured due to trapped gas bubbles
Sedimentary rocks primarily form through which sequence of processes?
Melting, crystallization, and foliation
Weathering, transport, deposition, then compaction and cementation
Metamorphism followed by melting and eruption
Compaction, melting, and rapid cooling
What is the key difference between sedimentation and lithification as defined in the material?
Sedimentation occurs after lithification
Sedimentation refers to weathering, transport, and deposition; lithification refers to compaction and cementation into rock
Both terms describe the same process
Lithification includes only weathering and transport
Which metamorphic rock correctly corresponds to its pre-existing rock?
Sandstone → Marble
Limestone → Quartzite
Shale → Slate
Granite → Schist
According to the list of abundant elements in Earth’s crust, which pair correctly shows the two most abundant and their approximate percentages?
Oxygen ~46.6% and Silicon ~27.72%
Silicon ~46.6% and Oxygen ~27.72%
Aluminum ~27.72% and Iron ~8.13%
Calcium ~5.00% and Sodium ~3.63%
Which statement best describes primary minerals?
They form from weathering of pre-existing minerals and are a source of clay fraction.
They form from crystallization of igneous rocks and are a source of sand and silt fractions.
They are exclusively clay minerals formed in soils.
They originate only from biological activity.
Which of the following is listed as a primary mineral example?
Kaolinite
Hematite
Olivine
Halite
In Bowen's Reaction Series, which branch includes Olivine, Pyroxene, Amphibole, and Biotite and is characterized by high magma temperature and low silica?
Residual phase
Continuous series
Discontinuous series
Secondary series
Which process is NOT a type of physical weathering described?
Exfoliation
Freeze–thaw
Oxidation
Abrasion
During chemical weathering, hydrolysis primarily results in which outcome?
Loss of electrons from minerals only
Attack of water causing changes in mineral composition or structure and decomposition
Removal of oxygen from minerals only
Cracking of rocks due to temperature changes
Which example correctly pairs a chemical weathering process with its description or result given in the notes?
Oxidation—gain of electrons by minerals
Reduction—removal of oxygen and gain of electrons
Hydration—destroys chemical structure of minerals
Carbonation—rocks or minerals with hydrochloric acid
Which statement about biological weathering is supported by the material?
It includes root wedging that widens cracks as roots grow and animal burrowing such as by piddocks.
It only involves microorganisms dissolving minerals in water.
It is synonymous with carbonation.
It consists solely of abrasion by wind-driven sand.
According to the five factors of soil formation, how does climate influence weathering and leaching?
Higher temperature slows biochemical reactions, reducing weathering.
Higher precipitation decreases leaching of soluble substances.
Higher temperature increases reaction rates, leading to faster weathering, and higher precipitation increases weathering and leaching.
Climate has little effect on soil formation compared to other factors.
Which role do microorganisms primarily play in soil formation according to the material?
They cause soil mixing through bioturbation
They help in decomposition of organic matter
They serve as the parent material for soil
They increase erosion on backslopes
In comparing grassland and forest soils, which statement is correct?
Grassland soils have a thin surface A horizon
Forest soils have a darker A horizon due to more organic matter
Grassland soils have a thick surface A horizon
Forest soils have no O horizon formation
Which hillslope position is most prone to flooding?
Summit
Shoulder
Backslope
Toeslope
Which transport agent matches the term aeolian in the context of parent material?
Water
Wind
Gravity
Ice
Which statement best defines the A horizon?
Layer of organic matter at various decomposition stages
Zone of eluviation where clay and oxides are leached
Mineral horizon in the topsoil where organic matter coats minerals causing darkening
Unweathered parent material
What key difference distinguishes the E horizon from the B horizon?
E is the zone of illuviation while B is the zone of eluviation
E is light colored due to leaching, while B is an accumulation zone of leached materials
Both are considered outside the zone of pedogenesis
E contains hard bedrock while B is unweathered parent material
Which horizon lies outside the zone of pedogenesis and consists of partially weathered parent material?
O horizon
C horizon
A horizon
B horizon
Haploidization refers to processes that do which of the following?
Differentiate initial materials into many horizons such as by illuviation and eluvia tion
Accelerate weathering to form hard bedrock
Inhibit, decelerate, or disturb horizon development, such as by erosion and pedoturbation
Create only organic horizons like Oi, Oe, and Oa
According to Simonson’s model, which set of processes drive soil formation?
Addition, removal, transformation, translocation
Weathering, erosion, deposition, cementation
Primary succession, secondary succession, climax
Oxidation, reduction, hydrolysis, carbonation
Which term under Addition refers to the accumulation on the soil surface of organic litter and associated humus to a depth of less than 30 cm?
Cumulization
Littering
Melanization
Enrichment
Which process is defined as the general term for washing out or eluviating soluble materials from the solum?
Erosion
Leaching
Illuviation
Lessivage
Which Transformation process involves the release of minerals (inorganic) of organic matter through decomposition?
Humification
Ripening
Mineralization
Synthesis
Salinization, alkalization/solonization, and dealkalization/solodization are categorized under which general process?
Addition
Removal
Transformation
Translocation
Which description best matches gleyization?
Chemical migration of silica out of the soil solum concentrating sesquioxides
Release of iron from primary minerals with progressive oxidation causing brownish to reddish colors
Reduction of iron under anaerobic waterlogged conditions producing bluish to greenish gray colors with mottles and concretions
Washing in suspension of fine clay down cracks and other voids
Which type of pedoturbation refers specifically to soil mixing by the action of clay shrinking and swelling?
Faunalturbation
Floralturbation
Argilliturbation
Cryoturbation
What is the smallest volume of soil that should be recognized as a soil individual?
Soil horizon
Polypedon
Pedon
Saprolite
Which statement best defines soil texture?
Arrangement of soil aggregates into horizons
Relative proportion of sand, silt, and clay in a soil
Amount of organic matter present in the topsoil
Degree of soil compaction due to machinery
According to the particle fraction table, which size range corresponds to silt in the USDA system?
> 2 mm
2 – 0.05 mm
0.05 – 0.002 mm
< 0.002 mm
A soil sample feels gritty when rubbed and is non‑sticky when moist. Which soil separate does this most likely indicate?
Sand
Silt
Clay
Gravel
Which chemical is commonly used as a dispersing agent to separate soil particles in the hydrometer method?
Lime
Calgon (Sodium hexametaphosphate)
Gypsum
Aluminum sulfate
Which pairing correctly matches a texture group comparison?
Coarse‑textured soils have low permeability
Fine‑textured soils have good drainage
Coarse‑textured soils have high bulk density
Fine‑textured soils have high water‑holding capacity
Which statement about aggregate stability and the slake test is most accurate?
Aggregate stability refers only to resistance against tillage tools
The slake test measures the stability of soil aggregates in water; stable macropores allow water movement without breaking aggregates
Aggregate stability is unrelated to wind erosion
The slake test is performed in dry air to prevent swelling
Which soil structure type is correctly matched with its typical occurrence or property?
Granular—forms in B horizon; very slow permeability
Blocky—common in A horizon; influenced by humus
Prismatic—forms in B horizon; moderate water permeability
Platy—forms due to good natural aggregation; rapid permeability
Which statement best defines bulk density (B.D.) of soil?
Ratio of mass of soil solids to the volume of soil
Mass of water per volume of pores
Ratio of pore space to total soil volume
Mass of soil solids per mass of water
Which is a listed effect of high bulk density in soils?
Improved porosity
High soil compaction and potential waterlogging
Increased organic matter
Enhanced soil aggregation
According to the notes, which factor lowers bulk density by improving soil aggregation?
Excessive tillage
Greater profile depth
Organic matter addition
Coarse soil texture
What is the typical particle density (PD) for mineral soils given in the material?
1.0 g/cm³
2.65 g/cm³
2.00 g/cm³
3.10 g/cm³
Which formula expresses percent pore space (porosity) in terms of bulk density and particle density?
% Pore space = (bulk density / particle density) × 100
% Pore space = 1 − (bulk density / particle density) × 100
% Pore space = (particle density − bulk density) × 100
% Pore space = (bulk density × particle density) / 100
Which pair correctly matches a water movement term with its description?
Infiltration: downward movement through soil layers by gravity
Percolation: entry of water via the soil surface
Infiltration: downward entry of water via the soil surface
Percolation: upward capillary movement
Which condition corresponds to the upper limit of available water for plants?
Saturation (0 bar)
Field Capacity (1/3 bar)
Permanent Wilting Point (15 bar)
Hygroscopic coefficient (31 bar)
How does soil moisture tension (SMT) change as moisture content decreases?
SMT decreases
SMT remains constant
SMT increases
SMT first increases then decreases
Which factor tends to slow infiltration according to the material?
Dry soil moisture content
Sandy (coarse) texture
Clayey (fine) texture
Well-aggregated soil structure
Available water is defined as the difference between which two moisture conditions?
Saturation and field capacity
Field capacity and permanent wilting point
Permanent wilting point and hygroscopic coefficient
Saturation and hygroscopic coefficient
According to the summary of water potential and tension, which situation makes water extraction difficult?
Low soil moisture tension
High soil moisture tension
High water potential in plant than soil
Water moving from higher to lower potential
Which soil behavior pairing with moisture content is stated in the table?
Dry: sticky and plastic
Wet: friable
Super saturated: viscous
Dry: viscous
Which list shows the Atterberg limits included in the material?
Liquid, Plastic, Friable, Hard
Liquid, Plastic, Elastic, Brittle
Liquid, Sticky, Plastic, Hard
Plastic, Viscous, Friable, Hard
What does the Munsell color chart describe soil color based on?
Hue and brightness only
Hue, Value, and Chroma
Value and saturation only
Chroma and texture
In the Munsell system, which term refers to the lightness or darkness of soil color and runs from 0 (pure black) to 10 (pure white)?
Hue
Chroma
Value
Tint
Which statement best describes soil colloids?
They are large sand-sized particles with low reactivity
They are very fine particles with high surface area and are chemically reactive
They are only organic in nature and non-reactive
They are visible to the naked eye and have no effect on soil properties
Which are the basic structural units of silicate clays?
Silica tetrahedron and aluminum octahedron
Calcium cube and magnesium prism
Iron hexagon and sodium pyramid
Carbon ring and hydrogen sheet
Kaolinite is categorized as which type of crystalline silicate clay and which property is typical of it?
1:1 non-expanding; low CEC and low surface area
2:1 highly expanding; high swelling and shrinkage
2:1 limited expanding; highest CEC
2:1 non-expanding; potassium ions dominate the interlayer
In montmorillonite, substitution of which ion by magnesium leads to a net negative charge?
Silicon is replaced by potassium
Aluminum is replaced by magnesium
Iron is replaced by calcium
Magnesium is replaced by aluminum
Which source of negative charge in clays is permanent and especially important for 2:1 layer silicates?
Isomorphous substitution within the crystal lattice
Ionization of exposed hydroxyl groups
Protonation of hydroxyl groups
Adsorption of organic acids from humus
What role do potassium ions (K+) play in illite (a 2:1 non-expanding clay)?
They cause high swelling by repelling sheets
They act as binding agents in the interlayer, holding tetrahedral sheets together
They substitute for aluminum in the octahedral sheet to create negative charge
They increase pH-dependent charges by deprotonation
Which statement about cation exchange in soils is correct?
It is an irreversible process that consumes cations
It is the movement of anions only in the soil solution
It is the reversible adsorption of cations on charged sediment surfaces and is stoichiometric
It occurs only in organic soils and not in clays
Which statement best defines Cation Exchange Capacity (CEC) in soils?
The total positive charges within the soil
A measure of the soil’s ability to hold and exchange positively charged ions
The percentage of soil organic matter
The mass of clay per 100 g of soil
Which soil property combination generally results in higher CEC?
Sandy texture with low organic matter
Clayey texture with high organic matter
Kaolinitic clay with low pH
Sandy loam with neutral pH
According to the table, what is the computed CEC (in me/100 g soil) from the listed exchangeable cations H+, Al3+, Na+, K+, Mg2+, and Ca2+?
12
18
23
27
Percent Base Saturation (%BS) is defined as the percentage of CEC occupied by which group of ions?
Anions such as NO3− and HPO42−
Hydrogen ions only
Basic cations such as Ca2+, Mg2+, K+, and Na+
Aluminum ions only
Using the provided example, what is the calculated percent base saturation if the sum of exchangeable bases is 1.5 + 2.5 + 6.0 + 9.0 and CEC is 23?
65.2%
78.3%
82.61%
90.0%
Which statement about soil pH is correct?
Acidic soils are dominated by OH− below pH 7
Neutral soils have pH 0
Alkaline soils are dominated by OH− above pH 7
pH equals log[H+]
Which of the following is a pool of acidity in soils?
Carbonate alkalinity in soil solids
Active acidity: H+ dissolved in soil solution
Base saturation: Ca2+ on exchange sites
Hydroxide ions in soil solution
Which source would most directly increase soil acidity according to the material?
Lime application
Crop removal and excess nitrogen fertilizers
High base saturation
Neutral pH water irrigation
Which statement best defines Relative Neutralizing Value (Calcium Carbonate Equivalent, CCE) as presented?
It measures the soil’s ability to carry electrical current.
It compares a liming material’s neutralizing ability to pure CaCO3.
It indicates the amount of exchangeable sodium in soil.
It is the percentage of organic matter in a soil sample.
Based on the table of liming materials, which has the highest Relative Neutralizing Value (RNV or CCE)?
CaCO3 (Calcium carbonate)
Ca(OH)2 (Slaked or Hydrated lime)
CaMg(CO3)2 (Dolomitic limestone)
CaO (Burned or Quick lime)
A soil with pH less than 7 and potential aluminum toxicity most likely falls under which problem soil category?
Saline soil
Acidic soil
Sodic soil
Saline-sodic soil
Which characteristic distinguishes saline soils from sodic soils according to the material?
Saline soils have high soluble salts; sodic soils have high exchangeable sodium.
Saline soils have pH above 9; sodic soils have pH below 5.
Saline soils show black surface crusts; sodic soils show white crusts.
Saline soils occur only in humid regions; sodic soils occur only in arid regions.
What is soil electrical conductivity primarily used to indicate in the field?
Soil texture class
Soil salinity
Soil organic matter content
Soil bulk density
How does flooding typically affect soil pH in acidic versus alkaline soils, according to the notes?
It decreases pH in both acidic and alkaline soils.
It increases pH in both acidic and alkaline soils.
It increases pH in acidic soils and decreases pH in alkaline soils.
It has no effect on pH but increases redox potential.
What product is primarily formed when methanogens use carbon dioxide as the terminal electron acceptor in highly reduced soils?
CO2
NO3−
SO42−
CH4
Which soil texture characteristic near beaches most directly makes maintaining a flooded rice field difficult?
High clay content causes waterlogging
Sandy composition causes rapid drainage
High organic matter retains too much water
Peat layers cause capillary rise
Rice generally prefers which soil pH range for optimal growth?
3.0 to 4.0
4.5 to 5.0
5.5 to 7.0
8.0 to 9.5
Why can low Cation Exchange Capacity (CEC) in coastal sandy soils hinder rice growth?
Low CEC increases nitrogen fixation by microbes
Low CEC reduces the soil’s ability to hold and exchange essential cations like Ca, Mg, K, and Na
Low CEC prevents soil aeration
Low CEC raises soil pH to optimal levels for rice
Which factor best explains why salinity near beaches can inhibit rice seed germination and plant growth?
Rice is tolerant to high salt levels
Sea spray and tidal action lower salt concentrations
Proximity to seawater elevates soil salt concentrations, and rice is sensitive to salt
High salinity increases nutrient availability
Which function is NOT listed as a role of soil organisms?
Decomposition
Nutrient cycling
Soil structure formation
Photosynthesis of leaves
Photoautotrophs are classified by which combination of energy and carbon sources?
Light for energy and carbon dioxide for carbon
Inorganic compounds for energy and organic compounds for carbon
Organic compounds for both energy and carbon
Light for energy and organic compounds for carbon
Which domain is characterized by prokaryotic cells without peptidoglycan in their cell walls and often inhabits extreme environments?
Eukarya
Bacteria
Archaea
Protozoa
Gram-negative bacteria are identified by which gram stain result and cell wall structure?
Purple stain; thick peptidoglycan layer, no outer membrane
Pink/red stain; thin peptidoglycan layer with outer membrane
Purple stain; thin peptidoglycan layer with outer membrane
Pink/red stain; thick peptidoglycan layer, no outer membrane
Actinomycetes are especially known for decomposing which resistant material?
Cellulose from plant cell walls
Chitin from insect exoskeletons
Lignin from woody plants
Starch from seeds
Which feature is associated with algae in soil and aquatic habitats?
Lack of photosynthesis and presence of flagella only
Presence of heterocyst (specialized cell) and photoautotrophic nature
Obligate anaerobic metabolism
Exclusively marine habitat with no freshwater members
Which pairing of bacterial oxygen requirement and description is correct?
Obligate aerobes: cannot survive in the presence of oxygen
Facultative anaerobes: use oxygen when available but can switch to anaerobic metabolism
Microaerophiles: require no oxygen at all
Aerotolerant: require high oxygen levels (20–100%)
Which type of earthworm lives in permanent burrows and drags surface leaf litter down into them?
Epigeic
Endogeic
Anecic
Parasitic
Soil organic matter includes decomposed or decomposing plant and animal material, microorganisms, and substances synthesized by soil organisms. Which of the following is NOT listed as one of its four components?
Living organisms (soil biota) <5%
Fresh residue ~10%
Stable OM (humus) 33–50%
Sand particles 33–50%
Which component of humus has the highest molecular weight and is darkest in color, and is insoluble in both acid and alkali?
Fulvic acid
Humic acid
Humin
Lignin
A lower C/N ratio in organic matter generally indicates which outcome?
Slower rate of decomposition
Faster rate of decomposition
No change in decomposition rate
Inhibition of microbial activity
During which composting stage do thermophiles replace mesophilic microorganisms to break down complex carbon sources, typically at 65–50°C?
Mesophilic stage
Thermophilic stage
Cooling stage
Maturation stage
Which process converts atmospheric nitrogen (N2) into a usable form primarily as ammonia (NH3) or related compounds?
Nitrification
Denitrification
Nitrogen fixation
Ammonification
In nitrification, which bacteria convert NO2− to NO3−?
Nitrosomonas
Nitrobacter
Azotobacter
Rhizobium
According to Mitscherlich's Law, what happens as nutrient levels approach sufficiency in the soil?
Growth response to added nutrient increases sharply
Each additional unit of nutrient gives progressively smaller growth increases
Plant growth stops regardless of added nutrient
Toxicity symptoms immediately appear
Which nutrient level is defined as adequate for optimal growth and results in healthy foliage and robust yields?
Deficient
Sufficient
Excess
Toxic
A plant shows chlorosis of older leaves, stunted growth, poor fruit and seed development, and overall reduced vigor. Which deficiency is most likely?
Nitrogen deficiency
Iron deficiency
Calcium deficiency
Sulfur deficiency
Which symptom best indicates phosphorus deficiency in plants?
Interveinal chlorosis on younger leaves
Dark green or purplish leaves, especially on older leaves
Leaf tip burn and marginal scorch on young leaves
Water-soaked lesions on stems
Potassium-deficient corn is most likely to show which field problem during the growing season?
Lodging late in the season due to poor stalk strength
Purple coloring of upper leaves only
Leaf tips sticking to the next lower leaf
Blossom end rot in fruits
Magnesium deficiency first appears as which pattern on corn leaves?
Uniform yellowing of the youngest leaves
Yellow to white interveinal striping of the lower corn leaves
Dark green banding along the margins of new leaves
Brown necrosis at the very tips of new leaves only
Which deficiency primarily shows symptoms in new leaves because the element is relatively immobile in plants?
Nitrogen
Potassium
Calcium
Magnesium
A plant exhibits interveinal chlorosis along the length of the upper leaves that become pale green to nearly white. Which nutrient is deficient?
Iron
Zinc
Copper
Boron
Which symptom is most characteristic of manganese deficiency in plants?
Olive green newly emerged leaves that may be slightly streaked
Purpling of stems with necrotic spots
Bronzing of leaves with iron plaques
Water-soaked lesions on older leaves
Sulfur deficiency is often confused with nitrogen deficiency. Which feature helps distinguish sulfur deficiency?
Yellowing is more pronounced on younger upper leaves
Yellowing appears first on the oldest lower leaves
Leaves develop interveinal purple coloration
Leaf margins curl downward while remaining dark green
Which soil and pH conditions favor copper deficiency according to the material?
Organic soils with high soil organic matter and high soil pH (above 7.5)
Acid sandy soils with low organic matter and low pH
Heavy clay soils with neutral pH
Waterlogged soils with low redox potential
A plant shows interveinal, light striping or a whitish band beginning at the base of the leaf and extending toward the tip, with the midrib and margins remaining green. Which nutrient is most likely deficient?
Zinc
Boron
Sulfur
Manganese
Which symptom is commonly associated with boron deficiency?
Leaves have small dead spots and are brittle
Purple coloration on older leaves only
Severe rolling of leaves with water-soaked lesions
Shortened internodes with dark green leaves
According to the fertilizer computation example, how many kg/ha of complete fertilizer (15-15-15) are needed to meet a 90-90-90 recommendation?
600 kg/ha
300 kg/ha
900 kg/ha
150 kg/ha
Using the provided example, approximately how many 50-kg bags of complete fertilizer (15-15-15) are required to meet the 90-90-90 recommendation?
12 bags
9 bags
6 bags
3 bags
For a fertilizer recommendation of 90-0-0, how many 50-kg bags of urea (46-0-0) are needed per hectare, based on the example?
About 4 bags
About 2 bags
About 6 bags
About 8 bags
How many tons of chicken manure (3-2-2) are needed to supply the limiting nutrients for a 90-90-90 recommendation, according to the example?
4.5 tons
3.0 tons
6.0 tons
1.5 tons
Which list shows the correct order of the six main hierarchical levels in the USDA Soil Taxonomy from highest to lowest?
Order, Suborder, Great Group, Subgroup, Family, Series
Series, Family, Subgroup, Great Group, Suborder, Order
Order, Great Group, Suborder, Subgroup, Series, Family
Family, Series, Subgroup, Suborder, Great Group, Order
Which soil order is described as recently formed soils with little or no evidence of pedogenic horizon development?
Inceptisols
Entisols
Alfisols
Mollisols
In the Philippines, which soil orders are explicitly noted as not found due to their defining conditions?
Gelisols, Aridisols, Spodosols
Ultisols, Oxisols, Histosols
Alfisols, Andisols, Vertisols
Mollisols, Inceptisols, Entisols
Which characteristic best distinguishes Andisols from many other soil orders?
Presence of permafrost
High base saturation in B horizons
Dominance of short-range-order compounds and high phosphorus-fixing capacity
Very low organic carbon content
A farmer in a dry region with limited water availability is most likely managing which soil order that forms in arid regions with limited change in parent material due to dryness?
Aridisols
Gelisols
Spodosols
Histosols
Which soil order is commonly utilized for rice production due to shrinking and swelling dark clay soils dominated by montmorillonite?
Vertisols
Ultisols
Oxisols
Spodosols
A soil is described as low-base status with finer-textured subsoils formed in acidic parent materials, commonly called “low activity clay,” and dominated by kaolinite. Which soil order fits this description?
Mollisols
Ultisols
Alfisols
Oxisols
