Appendix 1 Answers to Chapter Review Questions

Steve Earle

Answers for Chapter 1 Review Questions

  1. It is hypothesized that the Earth’s moon formed at around 4.5 Ga, when a Mars-sized planet smashed into the Earth and blasted a moon-sized part of the Earth into orbit around the Earth. That material, which included some of the incoming planet and some of the Earth’s early crust and mantle, eventually coalesced into the moon.
  2. Some parts that are included on Figure 1.2.1 but not on Figure 1.2.2 include (a) water from volcanic eruptions goes into the atmosphere and hydrosphere, (b) water from the atmosphere is incorporated into rocks during weathering, and (e) water from the ground is used by plants.
  3. The main role of the sun in powering ocean currents is via wind. The sun heats Earth surfaces differentially and this leads to convection in the atmosphere which creates wind. The energy of the wind is then transferred to the oceans creating both waves and currents.
  4. The key process is through weathering of rocks. Formations of mountains leads to increased rates of erosion and that enhances the rate of chemical weathering. The most important chemical weathering process—hydrolysis of silicate minerals—consumes carbon dioxide from the atmosphere. Volcanoes are mountains and volcanic eruptions add water and carbon dioxide to the atmosphere.  Mountains influence vegetation patterns and vegetation consumes carbon dioxide.
  5. Volcanic eruptions contribute CO2, SO2, and H2O to the atmosphere (along with a number of minor gases). Volcanic eruptions also cycle rock material from the mantle and lower crust to the upper crust and to surface. Volcanic mountains are also susceptible to erosion and weathering as outlined in the answer to question 4.
  6. Humans have changed Earth systems by: (i) cutting and burning forests, (ii) growing crops and cultivating the soil, (iii) burning fossil fuels, (iv) making concrete, (v) excavating rocks for mines, quarries, roads and buildings, (vi) making impermeable surfaces, (vii) putting waste into dumps and landfills, (viii) destroying and creating wetlands, (ix) using chemicals for agriculture, and (x) over-fishing.
  7. The breakdown of various components of the tractor has likely contributed to changes to the chemistry of the soil in the immediate area.  This might include acidification due to oxidation of metal parts, erosion of components of the painted surfaces, and dispersal of fuel and lubricants.

Answers for Chapter 2 Review Questions

  1. Calcite: carbonate, hematite: oxide, galena: sulphide, olivine: silicate
  2. Micas are sheets silicates (phyllosilicate), olivine has isolated silica tetrahedra (nesosilicate), quartz has a three-dimensional silicate framework (tectosilicate).
  3. The rock must first be exposed at surface (requires uplift and erosion of other rock in most cases), it then becomes susceptible to mechanical weathering (exfoliation, freeze-thaw, vegetation, etc.) and its minerals get chemically weathered (hydrolysis, oxidation, dissolution etc.). The fragments (pieces of rock, grains of sand, clay minerals) and ions in solution and then transported by various means and deposited as sediments.
  4. An existing sedimentary or igneous rock (parent rock) is buried beneath other rocks and subjected to elevated temperature, water and strong pressure. This leads to some of the minerals in the rock becoming unstable and being transformed into different minerals or to larger crystals of the same mineral.
  5. As a body of magma cools minerals start to crystallize (typically ferromagnesian minerals before others). If those minerals settle to the bottom of the magma chamber (because they are denser than the magma) that will make the composition more felsic at the top. If the minerals that have accumulated at the bottom then re-melt (because it is hotter at depth) the magma at the bottom will become more mafic.
  6. It takes time for crystals to grow in magma. The slower the cooling rate the more opportunity there is for large crystals to grow.
  7. A sand grain can range from 1/16th (0.0625) mm to 2 mm.
  8. A clastic sedimentary rock is made up mostly of fragments (clasts) of minerals and rocks (dominated by sand grains, silt and clay). A chemical sedimentary rock is made up mostly of ions that were transported in solution and then formed into mineral crystals at or near to the site of deposition. This can include fragments of shells.
  9. Foliation is a result of metamorphism that takes place when a body of rock is under directed pressure (greater pressure in one direction than in the others). This can result in deformation (squeezing) of the rock and also forces newly forming crystals to be orientated perpendicular to the main pressure direction.
  10. The continental crust is 30 to 40 km thick in most areas while the oceanic crust is mostly 5 to 6 km thick. The continental crust is made up a wide variety of rocks that are felsic on average, while the oceanic crust is made up mostly of mafic igneous rocks.
  11. The asthenosphere is a part of the mantle where the pressure and temperature conditions are such that the rock is close to its melting point. Some of the asthenosphere is molten, while most of it is relatively soft compared with the rest of the mantle. The mantle rock above the asthenosphere is too cool to be partially molten, while that below is under too much pressure to be partially molten.
  12. The Pacific Plate is moving generally northwest at 5 to 6 cm/y. The Africa Plate is moving generally northeast at 2 to 3 cm/y.
  13. At a subduction boundary water is forced out of the subducting plate (because the rock is heated) and moves upward into the overlying mantle rock. The mantle rock is already close to its melting point and the addition of water lowers the melting point enough to lead to partial melting. At a divergent boundary mantle rock is moving upwards due to mantle convection. This results in a reduction in pressure (without a corresponding reduction in temperature) and that reduces the melting point enough to cause partial melting.
  14. Because of the volcanism taking place at the centre of divergence, the temperature there is greater there than it is farther away. This temperature gradient leads to convection of water within the oceanic crust, with upward motion of water near to the boundary and downwards motion of seawater into the crust farther from the boundary, to replace the upward-moving water. (see Figure 2.5.1)

Answers for Chapter 3 Review Questions

  1. The sun, like other similar stars is slowly getting hotter because of the ongoing conversion of hydrogen to helium in the sun’s core. The growing proportion of helium results in an increase in the density of the solar core region, which causes the core to contract. The increased gravitational pressure forces the hydrogen atoms closer together, and that accelerates the rate of fusion and makes the sun hotter and brighter. This is not the cause of climate change. The increase in solar luminosity due to long-term solar evolution from 1920 to 2020 was only enough to increase the Earth’s surface temperature by about 0.0000016⁰ C.  During that time the surface temperature actually increased by about 1⁰ C, so it’s clear that solar evolution is not the cause.
  2. Life’s primary control over the climate for the past few billion years has been through photosynthesis, which consumes atmospheric CO2 and converts the carbon into plant tissues. A small proportion of those materials have buried along with sediments and safely stored in the crust.
  3. Land surfaces are generally brighter (higher albedo) than ocean water. Solar intensity is much greater at equatorial latitudes than at the poles. If the continents are concentrated near to the equator (making that area brighter than it would be otherwise) less of the sun’s energy will be absorbed on Earth so there will be less heating.
  4. The key process is through weathering of rocks. Formations of mountains leads to increased rates of erosion and that enhances the rate of chemical weathering. The most important chemical weathering process—hydrolysis of silicate minerals—consumes carbon dioxide from the atmosphere. Volcanoes are mountains and volcanic eruptions add water and carbon dioxide to the atmosphere.  Mountains influence vegetation patterns and vegetation consumes carbon dioxide.
  5. The ACC resulted in isolation of Antarctica from the rest of the ocean, preventing warmer water from reaching the continent, and resulting in significant cooling.
  6. SO2 gets converted to sulphate aerosols in the atmosphere (crystals and tiny droplets) and these block incoming sunlight, leading to short-term cooling (a few years).
  7. Higher than normal rates of volcanism would have to continue for several thousand years in order to result in sufficient buildup of carbon dioxide to warm the planet.
  8. Milankovitch cycles control which latitudes on the Earth receive the most solar energy (and which the least). Glaciation is favoured when there is less insolation at 65° N, and that triggers a range of different climate feedbacks to cool the climate.
  9. Insolation at 65° N should have left to cooling over the past 10,000 years, but in fact the Earth’s temperature has remained generally stable over that period.
  10. The Gulf Stream is strongest when its salty water cools and sinks in the far northern Atlantic. If the Gulf Stream weakens there will be less warm water surrounding western Europe and there could be climate cooling in that area.
  11. Weaking of ocean currents would result in less even distribution of heat on Earth, so warmer tropics and colder poles.
  12. There would have been killing heat from a meteorite storm, followed by intense wildfires all over North America producing nearly impenetrable smoke and ash, near darkness and then extreme cold for many months.

Answers for Chapter 4 Review Questions

  1. During the Cryogenian glaciations the Earth’s land surfaces were mostly covered with ice and snow and the oceans were almost completely frozen over, even at the equator.
  2. The main cause of Cenozoic cooling was mountain building in several areas, including the Himalayas.  Other cooling forcings were related to the development of the Antarctic Circumpolar Current and closing of the Isthmus of Panama.
  3. The first glaciation during the Cenozoic was in Antarctica, following development of the Antarctic Circumpolar Current.
  4. The Laurentide Ice sheet covered almost all of Canada east of the Rockies, and extended into the United States as far south as Wisconsin.
  5. Continental glaciers flow outward towards the margins from where the ice is thickest.
  6. The equilibrium line is the boundary between the zone of ice accumulation above (where not all of the snow from each winter melts in the following summer) and the zone of ice wasting below.
  7. Cool summers are more important to glacier growth than very cold winters.
  8. The bottom part of glacier move slower than the top, and the edges move slower than the middle.
  9. Basal sliding can take place where the base of the glacier is warm enough for ice to melt into water (as water acts as a lubricant) and the glacial ice isn’t frozen to the rocky substrate.
  10. Glaciers carve U-shaped valleys because they are wide enough to fill the valley (unlike a stream) and because most of the erosion takes place at the base of the ice. A hanging valley forms because tributary glaciers do not erode as deep into the terrain as main-valley glaciers.
  11. There are typically at least three cirques around a horn.
  12. A drumlin tends to be streamlined at both ends with a steeper slope at the up-ice end and a more gentle slope at the down-ice end. A roche moutonée typically has a steep irregular slope at the down-ice end because of rock plucking due to freezeing.
  13. From left to right they are lodgement till (well compacted clay-rich and poorly sorted, with clasts as large as boulders), coarse glacio-fluvial sediments (with gravel layers and sand layers), ablation till (poorly compacted and poorly sorted sediments with large angular clasts), and fine glacio-fluvial sediments (cross-bedded sand).
  14. A drop stone is an isolated pebble, cobble or boulder embedded in finer sediments (silt and/or clay). It forms when clasts fall from an ice berg floating on a lake or the ocean.
  15. During a strong glacial period there is a great deal of non-salty ice on land and less water in the oceans than there would be otherwise. That means that the oceans will be more salty than at other times.
(Steven Earle CC BY 4.0)

Answers for Chapter 5 Review Questions

  1. The normal and shear forces are shown by the blue arrows on the diagram to the right.
  2. The material on the slope remains stable under these conditions.
  3. The material would become prone to failure after several days of steady rain that makes it only half as strong.
  4. The blue lines on the diagram below represent bedding planes or fractures. The scenario on the left is at most risk of failure, while that on the right is at least risk.
  5. In moist sand there is a film of water surrounding each grain and the cohesion of that water to the grains helps to hold them together.
(Steven Earle CC BY 4.0)
  1. In a flow there is internal motion within the mass – it is moving like a fluid. In a slide the mass moves as a single unit.
  2. When moving quickly a body of rock will break into smaller pieces and if there is enough momentum this will start to flow like a fluid.
  3. A debris flow includes large rock particles (granules and larger) and often other debris (e.g., tree parts). Most of the material in a mud flow is sand or smaller, and it is likely that it is moving less quickly than a debris flow.
  4. They should have planned an escape route to a location that is deemed to be safe from lahars, and they should have created a household protocol (such as where to meet, what to bring, what not to bring, what to do with household animals) so that they can get away quickly.
  5. Steps must be taken to ensure that nothing is done during the construction process that will result in saturation of material on the slope by runoff from roofs, patios, driveways and roads.
  6. If a wasting mass flows into a stream it will result in a considerable increase in suspended sediment load. This is both because of the introduction of debris, but also because it is likely to increase the flow rate of the stream resulting in increased erosion of sediments from the stream bed.

Answers for Chapter 6 Review Questions

  1. An earthquake is the shaking of the ground surface caused by the rupture (breaking) and subsequent displacement of rocks (one body of rock moving with respect to another) beneath the Earth’s surface.
  2. The plates are always moving, but at plate boundaries, where one plate is moving with respect to another, they tend to be stuck. Under these conditions the rock on either side of the boundary will be elastically deformed.  That deformation will continue until it exceeds the strength of the rock, at which point the rock will break and the two sides will spring back to their undeformed state and the stored elastic energy will be released as seismic waves.
  3. A rupture surface is the area, at depth in the crust, over which rocks break during an earthquake. In many cases it is an area within a fault plane. The area of the rupture surface and the amount of motion of the rock on either side will determine the magnitude of the earthquake.
  4. An aftershock is an earthquake that was caused by stress transfer from another earthquake. When an earthquake happens some of the stress that existed in the rock is transferred to other bodies of rock nearby (e.g., to rocks along the same fault plane), bringing those rocks closer to failure, and in some cases to failure.
  5. Slow episodic slip on the middle part of the a subduction zone results in a transfer of stress to the upper part of the fault zone (where large earthquakes can occur), and so each time there is an episode of slow slip there is an enhanced risk of a large earthquake.
  6. Magnitude is a measure of the amount of energy released by the earthquake. Intensity is an assessment of what was felt by people and what damage was done.
  7. A magnitude 7.3 earthquake releases about 1024 times as much energy as  a magnitude 5.3 earthquake (based on the principle that each unit step in the magnitude scale represents 32 times as much energy as the previous step).
(Modified drawing by Steven Earle. Drawing used with permission of Dale Sawyer, Rice University, All rights reserved.)
  1. It is an ocean-continent subduction boundary.
  2. The dark blue toothed line shows where the plate boundary is situated.
  3. The oceanic plate is moving east relative to the continental plate. This area is along the western coast of South America.
  4. Most earthquakes that happen near to divergent boundaries actually occur on the transform faults that connect the segments of the divergent boundary.
  5. One is the San Andreas Fault that cuts across California, the other is the Queen Charlotte Fault that lies offshore from British Columbia near to Haida Gwaii. Both are associated with relatively frequent strong earthquakes.
  6. Earthquakes produce seismic waves with a wide range of frequencies. The higher frequency waves tend to be absorbed by the solid rocks of the crust, while the lower frequencies pass through the rock without losing much energy. Those slower-vibrating waves have frequencies that are similar to the natural vibration frequencies of unconsolidated surface materials and that match in frequencies leads to amplification of seismic shaking. If the surface materials are saturated with water, there is also a risk of liquefaction.
  7. Fires are common during earthquakes because earthquakes can result in rupturing of underground gas lines and in downing of overhead power lines. The combination of leaking gas and electrical sparks leads to fires.
  8. A tsunami is most likely to be caused by a subduction earthquake that results in vertical motion of the sea floor. Significant tsunami waves are only likely if the earthquake magnitude is over 7.
  9. The 2004 Parkfield earthquake was associated with no measurable precursors in any of the many geophysical parameters that were monitored and there was no foreshock. In other words, the experiment provided no evidence that earthquake prediction was feasible in this geological setting (a transform fault).
  10. We should try to understand (a) the history of earthquakes in the area (based on seismic records, historical reports, and on geological information) (b) the relative plate motions and plate interactions of the region, (c) the known faults and their sense of motion, (d) the degree of deformation of the crust across the region, (e) the types of materials underlying built-up areas (and specifically the existence of thick deposits of unconsolidated sediments, and the state of saturation of those sediments), and (f) any historical information on how different parts of the reason have responded to past earthquakes.

Answers for Chapter 7 Review Questions

  1. Volcanism can take place along spreading boundaries (mostly on the sea floor), at convergent boundaries (above subduction zones), and above mantle plumes.
  2. At a convergent boundary the subducting plate gets heated as it descends into the mantle. This forces liquid water out and also releases water from minerals like serpentine. The water from these processes rises into the overlying mantle where it reduces the melting temperature of the mantle rock and leads to flux melting.
  3. Viscosity controls the degree to which gases can escape from magma and whether or not magma will be able to escape to surface.  Viscous magma cannot flow easily through small openings and will also retain gases. Those factors will lead to an increase in pressure. When something breaks there will be an explosive eruption and the resulting rock will have a pyroclastic texture. Non-viscous magma can escape and release gases more easily, and so the magma is more likely to flow out in an effusive eruption creating a lava texture.
  4. Gases remained dissolved in the magma when it is under pressure and therefore take up negligible space.
  5. There are two important processes. One is fractional crystallization, which is the crystallization of some minerals – typically ferromagnesian minerals – before others. If those minerals settle to the bottom of the magma chamber that will make the composition more felsic at the top and more mafic at the bottom. The other is partial melting of the surrounding rock, or of xenoliths that fall into the magma, both of which are likely to make the magma more felsic overall.
  6. Composite volcanoes typically have both lava flows and pyroclastic deposits because the composition of the magma can be quite variable.
  7. A lahar is a flood, debris flow or mud flow that forms on a volcano. They are most common on composite volcanoes and are not necessarily caused by an eruption. But if there is an eruption there is a risk that snow and ice near the volcano summit will melt rapidly and lead to a lahar.
  8. A lahar can also form as a result of heavy rains in a volcanic region, leading to flooding and to destabilization of volcanic deposits that are not well consolidated (e.g., pyroclastic deposits).
  9. Composite volcanoes tend to be steeper than shield volcanoes because of the potential for pyroclastic eruptions which create deposits that – for the most part – do not extend as far away from the summit as a lava flow would.
  10. A pyroclastic density current is a rapid downslope flow of hot pyroclastic fragments and hot gases associated with an explosive volcanic eruption. They are dangerous because they are lethally hot and can move at 10s of km/h.
  11. Movement of magma beneath the volcano can result in small breakages of rock that create seismic events.
  12. GPS allows us to monitor the shape of a volcano.  If there is any evidence of expansion of the volcano that’s likely because magma is rising to surface and that’s a precursor to an eruption.
  13. Volcanic deposits tend to weather readily, and so their chemical nutrients become available to plants quickly.
  14. Most of the deaths from the 2002 eruption of Mt. Nyiragongo (Congo) were due to asphyxiation from carbon dioxide. Some were from lava flows that led to collapse of buildings.
  15. Mantle rock is compositionally very different from most crustal rock and so its presence at surface provides a source of elements that are not otherwise available to surface Earth system (e.g., plants).

Answers for Chapter 8 Review Questions

  1. The key components of a typical lithium ion battery are copper, nickel, cobalt, aluminum and lithium.
  2. Mafic and ultramafic magmas tend to have much higher background levels of nickel than felsic or intermediate magmas. So there is more nickel present in the first place and a better chance that magmatic concentration processes will produce ore-grade rock.
  3. The “smoke” is mostly made up of tiny crystals of sulphide minerals. Most of those are iron sulphides like pyrite, but they might include ore minerals such as chalcopyrite (CuFeS2) or sphalerite (ZnS).
  4. Both are likely to be related to an intrusive igneous body (magma chamber) that is present in the upper part of the crust. The porphyry deposit will likely form very close to the magma, while the epigenetic gold deposit will form farther away.
  5. Uranium is most soluble in its oxidized form (U6+) but the uranium will precipitate as uraninite (UO2) when it encounters less oxidizing conditions and the uranium is converted to the U4+ form. Iron is most soluble in its reduced form (Fe2+) but it will precipitate as either hematite (Fe2O3) or magnetite (Fe3O4) when it encounters more oxidizing conditions and the iron is converted to Fe3+.
  6. The lithium-bearing brines need to be evaporated to concentrate the lithium and the sun is used as an energy source for that process.
  7. Pyrite (FeS2) is the main source of acid rock drainage. It is a very common mineral within and peripheral to mineral deposits as it often forms by the same processes as the ore minerals.
  8. Glaciofluvial sediments, like all fluvial sediments, tend to be relatively well sorted, and, in most cases, have very little clay. Till is comprised of sediments ranging in size from clay to boulders (it is poorly sorted), and is also typically well compacted, so is not as easily processed into usable aggregate.
  9. The process of heating limestone to produce lime requires heat energy, and that is normally supplied using fossil fuels, so CO2 is emitted. The chemical process also emits CO2 (CaCO3 → CaO + CO2).
  10. Some important evaporite industrial minerals include salt (NaCl), sylvite (KCl), gypsum (CaSO4.H2O), and lithium carbonate.
  11. Under the situation described it would take 15,000 years to stable conditions to accumulate enough organic matter to form a 1.5 m coal seam.
  12. Petroleum source rocks must have high levels of organic matter that can be converted to hydrocarbons, and petroleum reservoir rocks must have sufficient porosity to store petroleum and sufficient permeability that it can be extracted.
  13. Organic matter in sedimentary rocks can be converted into oil at depths of approximately 2 to 4 km.
  14. Shale gas is “unconventional” because shale is normally too impermeable to allow for gas recovery. That can be overcome by hydro-fracturing the rock, but that process uses large amounts of chemical-rich water under very high pressures and there is a risk that some of that water (and some of the formation water) will escape into and contaminate overlying aquifers. Fracking companies are not required to reveal the composition of their fracking fluids.
  15. Our use of fossil fuels is changing the climate and the implications of that are becoming increasingly dangerous for us and for ecosystems, and also incredibly expensive. We need to stop using fossil fuels very quickly so that we can limit the amount of damage to the Earth and its inhabitants.

Answers for Chapter 9 Review Questions

  1. Southern Saskatchewan has a much sunnier climate than southern British Columbia, and fewer large trees and mountains to block the sun.
  2. A typical process in a solar-thermal plant is to heat up molten sodium, and then use the heat in the sodium to run a steam turbine. In what way is that a significant advantage over using the solar heat to create steam directly?
  3. A run-of-river hydro project does not involve the flooding of land, and although it does require that water be extracted from the stream, the uncontaminated water is returned to the stream a little farther down.
  4. Tidal energy can be captured by placing turbines in areas where there are natural strong tidal flows, or by building a barrage (dam) on an estuary and then forcing the water to flow through a turbine via a penstock.
  5. Geothermal heat can be used for district heating and for pools and spas. In some areas it is also used to keep roads and walkways free from snow and ice.
  6. The heat that is captured in a geo-exchange system comes from the sun, not from the Earth’s interior.
  7. Nuclear fusion doesn’t require fuel to be mined and doesn’t produce significant amounts of toxic waste or any other waste.
  8. Answers will vary by region.
  9. One of the difficulties with energy systems in general, and some renewable energy systems in particular, is that there are wide variations in the demand for electricity (from hour to hour, and from season to season) and also variations in the rates of production. Energy storage can help smooth out some of the short-term variations (by allowing us to store energy and use it later in the day) and regional grid interconnections can help smooth out both short- and long-term variations by allowing us to move energy from one location to another.

Answers for Chapter 10 Review Questions

  1. The rock must have been formed under high pressure (e.g., granite, gneiss) within the crust, and then was uplifted and exposed by erosion of the rock overhead, releasing the pressure, allowing the rock to expand and crack.
  2. It is typically consistently too cold in winter (stays below freezing most days) and too warm in summer (doesn’t freeze), so the most likely times for freeze-thaw mechanical weathering are spring and fall when days are above freezing and many nights are below freezing.
  3. Hydrolysis of albite (NaAlSi3O8) will likely lead to the formation of the clay mineral kaolinite (Al2Si2O5(OH)4) and to the release of Na+ ions into solution. A key step in the process is the dissolution of some atmospheric CO2 to make carbonic acid. That carbon will remain in solution, eventually being transported to the ocean.
  4. Acid rock drainage results in elevated acidity in surface water. The more acidic water also promotes the dissolution of heavy metals, such as copper, zinc and lead, and the higher concentrations of those can be toxic to aquatic life.
  5. Feldspar is much more susceptible to chemical weathering than is quartz, so feldspar is only likely to survive erosion and transportation if the conditions are unsuitable for chemical weathering (cold and dry) and the transportation is relatively short.
  6. The clay minerals tend to stay in suspension in moving surface water and so are transported into lakes and into the ocean.  Most of the clay ends up on the ocean floor.
  7. Soil cannot accumulate if the slope is so steep that loose material slides down. Parent materials influence the texture of the soil and can result in it being sandy (if the parent rock has lots of quartz) or clay rich (if the parent rock is volcanic or mudstone). Parent materials also influence the soil chemistry, providing important nutrients that are present in the rock – such as phosphate from the mineral apatite, or potassium from K-feldspar.
  8. Iron and aluminum ions move downward to accumulate within the B horizon of a soil.
  9. The main processes that lead to the erosion of soils in Canada (and elsewhere) are water and wind, and the main anthropogenic reason for soil erosion is the removal of vegetation.
  10. Chernozemic soils are most common in the southern prairie provinces and the valleys of the southern interior of British Columbia, areas which have very dry summers.
  11. The octahedral layer of a sheet silicate is made up of octahedra of aluminum, oxygen and hydroxyl ions. The tetrahedral layer is made up of tetrahedra made up of silicon and oxygen.
  12. Clay minerals are relatively weak compared with other silicates and so they make the rock that they are present in generally weaker than non-clay-bearing rocks. They become even weaker when they are saturated with water.
  13. Clay minerals have very high surface areas and those surfaces tend to be negatively charged due to the oxygen ions. Clays are therefore effective at absorbing metals, which typically exist as cations.

Answers for Chapter 11 Review Questions

  1. Glacial ice holds most of the fresh water on Earth, and the largest single reservoir of glacial ice, by far, is the Antarctic ice sheet.
(Steven Earle,  CC BY 4.0)
  1. The approximate outline of the drainage basin of Red Dog Creek is shown by the red dashed line.
  2. The volume of the lake isn’t relevant to the answer, only the discharge of the outflow stream (8 m3/s). It would be possible to extract 2 m3/s and still leave 75% for down-flow users. If the lake level increases during the wet part of the year, then it may be possible to extract at a slightly higher rate, as long as it didn’t lead to a long-term drop in the lake’s elevation.
  3. The main issue is the size of the pores in silt versus sand.  Because the pores are very small in silt almost all of the water within them is very close to a grain boundary, and thus held by adhesion to the grains.
  4. An artesian well is one in which the water level rises above the upper surface of the aquifer. This can be the case where parts of the aquifer are situated at a higher elevation than where the well is drilled.
  5. The formula to use is V = Ki/n (velocity = (permeability * gradient)/porosity), so (0.00001 m/s * ((54-45)/180))/0.20, which becomes (0.05 * 0.00001)/0.2 = 0.0000025 m/s, or 2.5 * 10-6 m/s.
  6. Dissolved constituents are present at higher levels in groundwater than in surface water because the water within the ground has very close contact with the materials of the aquifer.  This is especially true in the case of granular aquifers (as opposed to fractured-rock aquifers) where every grain is surrounded by water.
  7. Hardness is determined as the sum of calcium and magnesium, so sample A has the highest hardness.  (Sample A: 55 mg/L Ca2+, 8 mg/L Mg2+, Sample B: 30 mg/L Ca2+, 12 mg/L Mg2+)
  8. Fluoride solubility is highest where calcium levels are low, so sample B is likely to have the highest fluoride level.
  9. The most significant problem with turbidity in drinking water is that it inhibits the effectiveness of disinfection methods because microorganisms may gain some protection from chlorine or ozone if they are attached to clay particles, or may be hidden from UV light.
  10. Agricultural fertilizers help crops to grow but they also promote the growth of aquatic algae and so lead to significant and potentially dangerous algal blooms.
  11. Fossil fuels can include components that are volatile (evaporate into gases), lighter than water, heavier than water, and soluble in water. All of these different phases can be dispersed in different ways within an aquifer, and all can have negative impacts for ecosystems and for people.

Answers for Chapter 12 Review Questions

  1. When mixed with water carbon dioxide creates carbonic acid and this is a key reagent in the dissolution of limestone.
  2. Soil is  important to the formation of carbonic acid (and limestone dissolution) because soil tends to have much higher CO2 levels than the atmosphere.
  3. Exokarst includes the features found on the surface of the karst landscape including karren, sinkholes and poljes, while epikarst is the zone beneath surface where water, air, and various sediments are transferred from the surface to the subsurface through karst openings.
  4. The phreatic zone is the part of a karst system that is beneath the water table. Openings in the phreatic zone are always filled with water.
  5. Groundwater in a karst aquifer is likely to have higher levels of calcium, magnesium and bicarbonate and lower levels of sodium than that in a sandstone aquifer.
  6. Karst can form in areas underlain by soluble rocks such as dolostone, gypsum, halite, and in rare cases less soluble rock like sandstone and quartzite.
  7. A speleogen is a rocky feature found on the interior surface of a cave which is the result of chemical dissolution, mechanical erosion, or a combination of these processes. A speleothem is  mineral deposit—such as a stalactite or stalagmite— within a cave formed as a result of a reduction in the solubility of calcium carbonate in water within the cave.
  8. The solubility of calcium carbonate is controlled by the level of CO2 in the surrounding air. If the CO2 level decreases, calcium carbonate will become less soluble and some of the Ca2+ and HCO3- ions in the water will precipitate as calcium carbonate.
  9. Authigenic (or autochthonous) sediments are made up of material that formed within a cave. Allogenic (or allochthonous) sediments are made up of material that was introduced into a cave from outside.
  10. Troglophiles are creatures that can spend their entire lives in caves but that can also live in similar dark and damp surface environments.
  11. It is currently hypothesized that most limestone karst genesis takes place near to the boundary between the phreatic and vadose zones.
  12. A multi-level cave system may develop if there are changes in the groundwater base level (the water table).  Most commonly this would take place if the base level us lowered.

Answers for Chapter 13 Review Questions

  1. The higher the water table within a drainage basin (which is equivalent to the amount of groundwater stored) the higher the base-level discharge from the tributaries and the main stream.
  2. When a stream overtops its banks and occupies its flood plain and the area available for the water flow increases dramatically and the velocity decreases.
  3. The amount of water that a tropical storm brings onto land is largely proportional to the temperature of the air and of the water that it passes over. With climate change both of those have increased and so Hurricane Harvey brought a tremendous amount of water onto land.  It then stalled over the Houston area of Texas and dropped most of that water in that area.
  4. A slope failure can result in a large mass of debris entering a stream channel, potentially damming up the stream flow. When the backed-up water overtops the dam (or even before it does) the water can quickly erode though the debris unleashing a flood of water.
  5. The runoff from the urban area is likely to be 6 times that of the forested area (0.84/0.14 = 6), although this could vary depending on the total amount of rain and the rate of rainfall. A light rain over a long time may not produce much runoff from either area.
  6. A dam can be used to moderate the flow on the stream below if water is released during dry periods and then held back during very wet periods. If the dam is also used to produce energy the operator may choose to let as much water flow as possible when the demand is high, and this could compromise the flood-control function of the dam.
  7. Wing dykes on a stream act like partial dams. They reduce the rate of water flow and that can exacerbate flooding in upstream areas. Dykes along the side of a river prevent flooding in that area so that water that might otherwise have been temporarily stored on the flood plain quickly passes through, increasing the potential for flooding in downstream areas.
  8. Much of the area that is now part of the Grand Forks Greenway was formerly occupied by impermeable surfaces such as roads, parking lots and buildings so that water flowing through was unable to soak into the ground. The now more permeable surfaces allow water to soak in, reducing the risks of flooding here and farther downstream.  Furthermore, the infrastructure within the Greenway has been designed so that it is not significantly damaged by flooding.

Answers for Chapter 14 Review Questions

  1. It is critical to keep organic matter (kitchen waste, yard waste, paper etc.) out of landfills because those are the components that are most effective at producing methane and carbon dioxide.
  2. Daily cover prevents birds and other animals from dispersing the waste, it keeps some of the rain water out of the waste, and it reduces the odors from the landfill.
  3. Inactive sections should have an impermeable cover to keep extra water out of the waste, and to allow the capture of landfill gases. A cover also prevents access from animals and reduces the odor.
  4. It is common for landfill water monitoring protocols to include a very wide range of constituents, including many that are not known to be an issue with landfill leachates. That said, the constituents that might be most effective at detecting leakage would include many of those listed in Table 14.3.1., especially the ones that are typically present at high levels in leachates compared with natural waters: COD, BOD, ammonia, chloride, sodium, magnesium, potassium, calcium, and iron.
By S. Earle, CC BY 4.0
  1. Landfill gas is primarily composed of methane and carbon dioxide, in roughly equal proportions.
  2. Landfill gas that isn’t used as an energy source should be flared in order to convert the methane to carbon dioxide because methane has a much greater greenhouse climate effect than carbon dioxide.
  3. (Steven Earle CC BY 4.0, based on data from Tetra Tech. 2016)

    The major non-combustible components of typical landfill waste are glass, metals, and electronics, and some parts of the hazardous waste.

  4. The main issues from the perspective of human health are bacteria, viruses, protozoa and parasites. From the perspective of ecosystem health the main problems are nitrogen phosphorous, and heavy metals.
  5. Liquid wastes from a septic system will be filtered and decontaminated on passing though appropriate natural or imported surficial materials (e.g., sand or fine gravel). This will be most effective if the materials are sufficiently impermeable to allow liquids pass through slowly.  If the materials are too impermeable the liquid will not be able to drain away adequately and may start to pool at surface.

Answers for Chapter 15 Review Questions

  1. Climate change has contributed to an increase in wildfire activity in at least three ways: a) less rainfall in some areas has made vegetation drier and more flammable, b) higher temperatures have also contributed to drying of vegetation and c) warmer temperatures have allowed forest pests such as the Mountain Pine Beetle to kill trees and make them more vulnerable to fire.
  2. Northern latitudes have experienced more warming than the rest of the world because there is more land in the northern hemisphere and land warms more quickly than oceans, and also because the dramatic loss of sea ice in the Arctic Ocean has resulted in more solar warming there (because of albedo change).
  3. Warm air can hold more moisture than cool air and so there is more water available for precipitation in some areas. Those areas may not be noticeably wetter than before because there is also more evaporation and evapotranspiration. Warmer ocean water increases the water content of tropical storms and so can lead to much higher than normal localized precipitation.
  4. For the past tens of thousands of years alpine glaciers have pressed up against valley walls, compressing the rock and allowing it to maintain steep slopes. With the thinning and recession of glaciers that support is being lost and rock faces are also expanding and losing strength, increasing the probability of slope failure.
  5. Based on the long-term trend, the annual rate of sea level rise from 1880 to 1900 was 25 mm / 20 y = 1.25 mm/y. The rate from 2000 to 2013 was 38 mm / 13 y = 2.9 mm/y. If we use annual values instead, the rate was still close to 1.25 mm/y for the 1880 to 1900 period, but was more like 3.6 mm/y (47 mm / 13 y) for the 2000 to 2013 period.
    (Steven Earle, CC BY 4.0, based on public domain data from Global Average Absolute Sea Level Change, 1880-2014, US Environmental Protection Agency using data from CSIRO, 2015; NOAA, 2015,
  6. Vast amounts of methane and carbon dioxide are stored in permanently frozen soil (permafrost). When permafrost melts and the soil becomes unstable (resulting in slope failure) those gases are released.
  7. Tropical storms are powered by the thermal energy stored in near surface ocean water. The frequency and strength of tropical storms has increased in recent decades as a result of this change. Larger storms developed in a warmer atmosphere can extract more water from the oceans, and so tropical storms are transporting much more water onto land, resulting in serious flooding. Flooding is also exacerbated because of an increase in the area of impermeable surfaces due to residential and commercial development and construction of more and bigger roads and highways.
  8. The rate of weathering of rocks (e.g., oxidation and hydrolysis) is proportional to erosion rates (and so formation of mountains) but also to temperature, humidity and the carbon dioxide level of the atmosphere, all of which are higher as a result of anthropogenic changes.
  9. Answers will vary depending on personal habits and location, but for most of us the answer is to drive less (much less!) or, if that’s not possible, to drive an electric car.


Appendix 1 Answers to Chapter Review Questions Copyright © by Steve Earle. All Rights Reserved.

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