weathering and sedimentary rocks (LEC 4)

Question 1

most common external processes,
hint: weathering

Answer 1

weathering
erosion
mass wasting (movement of rock/soil downslope)

Question 2

what is weathering

Answer 2

breakdown of earth’s materials

Question 3

when rocks are broken down, particle size ____________ and surface area _____________
words: increases, decreases

Answer 3

decreases
increases

Question 4

what are the types of weathering

Answer 4

mechanical and chemical

Question 5

what is mechanical weathering chemical weathering

Answer 5

*physical breakdown of rocks without changing the composition
*breakdown of rocks by chemical reactions mainly reactions with air
or water and resulted in one or more new compounds

Question 6

examples of mechanical weathering

Answer 6

• frost action (freezing and thawing)
• pressure release (sheeting)
• biological activity

Question 7

important agents of chemical weathering:

Answer 7

• atmospheric gases (mainly oxygen)
• water (the most important agent)
• organic acids (produced by plants and decaying of organic matter)

Question 8

chemical weathering mechanisms (3)

Answer 8

1. dissolution
2. oxidation
3. hydrolysis

Question 9

sources of acids (3)

Answer 9

1) carbonic acid is produced from the CO2 in the atmosphere
2) sulphuric or nitrous acids are introduced in acid rains
3) various organic acids are released into soil as organisms decay

Question 10

oxidation reactions are very slow in dry environments, what speeds up the oxidation reactions

Answer 10

water

Question 11

factors affecting the chemical weathering rate (2)

Answer 11

rock characteristics
climate

Question 12

___________ silicate in the rock, increases its resistance to weathering
high silicate content results in low rate of chemical weathering

Answer 12

increasing

Question 13

high temperature = high/low weathering
dry climate = high/low weathering

Answer 13

high
low

Question 14

old rocks > small particles > sediments > SOIL

Answer 14

slay

Question 15

soil: parent materials can be either _________ (residual soil) or ________________ (transported soil)

Answer 15

bedrock; unconsolidated materials

Question 16

climate is the most influential parameter for soil formation
hot, wet climate = ______ layer of chemically weathered soil
cold, dry climate = ______ layer of mechanically weathered soil

option: thin/thick

Answer 16

thick
thin

Question 17

the optimum topography for soil formation is flat, why

Answer 17

because of low moisture content and high erosion in a steep slope will create poorly developed soil

Question 18

soil horizons are separated layers that
differ from one another in _____, _______, _______, and _______

Answer 18

colour, texture, structure, and composition

Question 19

define eluviation

Answer 19

when water percolates downward,
it carries FINE PARTICLES to a deeper zone

Question 20

soil colour is generally a reflection of its composition:
high organic matter = what colour?
high Fe = what colour?

Answer 20

black or brown
red or yellow color

Question 21

high particle size = high _________

Answer 21

leachate

Question 22

which rocks are the only rocks that contain fossils

Answer 22

sedimentary rocks

Question 23

calcite, iron oxide, silica, what are these?

Answer 23

the most common cements

Question 24

identification of cements:
________ = bubble with dilute HCl
________ = the hardest cement
________ = orange or dark red color

Answer 24

calcite
silica
iron oxide

Question 25

two main types of marines and their depths

Answer 25

shallow marine (less than 200 m depth) deep marine (more than 200 m depth)

Question 26

name the continental environments (3)

Answer 26

alluvial fan sand dunes playa lake

Question 27

name the transitional environments (3)

Answer 27

tidal flats beach delta

Question 28

sedimentary rocks are classified based on their composition into three main types:

Answer 28

*clastic (detrital) :pieces of rocks derived by mechanical or chemical weathering *chemical (crystalline): dissolved compounds in solution precipitate due to evaporation or oversaturation. *biological (bioclastic): remains of living organisms or plants or materials produced by organic (biological) precipitation

Question 29

three characteristics of clastic sedimentary rocks that can give us information about their deposition environment:

Answer 29

* particle size * sorting * roundness

Question 30

the final deposit reflects the combined influence of environmental energy and sediment availability

Answer 30

idk how to create a question from this....... LOL

Question 31

well sorted sediment (the grains in the sample are about same size) = deposited by _______ poor sorted sediment (the grains in the sample are different sizes (mixture of large and small sizes) = deposited by _______ options: water, wind

Answer 31

wind water

Question 32

main types of clastic sedimentary rocks (5)

Answer 32

* mudrocks * shale * sandstone * conglomerate * breccia

Question 33

mudrocks are the _____ common type of sedimentary stone, they form from sediments deposited in a quiet water environment (lakes, lagoons, deep-ocean basin)

Answer 33

most

Question 34

why is groundwater usually underlain by shale bed

Answer 34

shale consists of very small particles which result in microscopic pore spaces which don’t permit water to infiltrate, restricting the movement of groundwater through the shale rock

Question 35

types of sandstones (composition) (3)

Answer 35

* quartz sandstone * arkose * wacke

Question 36

main types of clastic sedimentary rocks

Answer 36

conglomerate and breccia

Question 37

precipitate can be inorganic or organic material: inorganic = _____________ organic = _____________

Answer 37

chemical sedimentary rock biological sedimentary rock

Question 38

examples of: chemical precipitates biological precipitates

Answer 38

*ex. halite, calcite, and gypsum halite: dissolved sodium and dissolved chloride, when concentrated enough, produce sodium chloride (halite). *fossil remains of plants and animals

Question 39

common chemical sedimentary rocks (4)

Answer 39

limestone dolostone chert evaporites

Question 40

_______ soluble minerals precipitate first options: more/less

Answer 40

less

Question 41

stages of coal formation: (accumulation of plant remains) > 1. plant material (plants remains) > (partial oxidation by bacteria) > 2. peat (soft brown materials) > (shallow burial increase in T&P) > 3. lignite (soft brown coal) > (deep burial, the water and volatiles are pressed out) > 4. bituminous [hard, more compacted black coal (rock)]

Answer 41

that was not a question :) but just memorize it like so: 1. remains → partial oxidation 2. p(EAT) → soft brown 3. l(IGNITE) → brown coal 4. bit[(L)uminous] → black coal

Question 42

carbon content in different coal stages

Answer 42

peat > lignite (carbon content = 25 to 35%) > bituminous (carbon content = 45 to 86%) > anthracite (carbon content = 86 to 97%)

Question 43

sedimentary structures are features formed from sediments during or shortly after deposition. common types of sedimentary structures:

Answer 43

* bedding * mud cracks * ripple marks

Question 44

bedding: beds or strata are layers of sediments accumulated in various depositional environments. three main types of bedding:

Answer 44

* parallel-bedding * cross-bedding * graded-bedding

Question 45

parallel-bedding: the layers are parallel and typically horizontal so what is cross-bedding

Answer 45

when the layers are inclined to horizontal

Question 46

what are graded-beds

Answer 46

when the particles within a single layer gradually change from coarse at the bottom to fine at the top

Question 47

what are mud cracks

Answer 47

when wet mud is exposed to air and dries up, it cracks

Question 48

what are ripple-marks

Answer 48

small waves of sand on the surface of a sediment layer by the action of moving water or air

Question 49

fossils are the remains or traces of prehistoric life now preserved in rock * fossils are generally found in _______ rock and rarely in _______ rock, but never in _______ rock

Answer 49

sedimentary metamorphic igneous

Question 50

define leaching

Answer 50

when water percolates downward, it carries dissolved INORGANIC MATTER to a deeper zone