part iii (15-23)

Question 1

List the sequence of events that breaks down old rocks and forms new sedimentary rocks from them

Answer 1

Weathering and erosion move broken down rocks down stream to ocean; sediment settles in the sea and is then lithified; the sediments that are buried and subjected to a lot of pressure form new sedimentary rocks

Question 2

Explain two ways that a sedimentary rock can be lithified

Answer 2

1) Compaction: burying sediment and weight eventually squeezes water out to solidify the sediment

2) Cementation: precipitation or addition of new materials cements sedimentary particles

Question 3

Explain the difference between clastic and (bio)chemical sedimentary rocks

Answer 3

Clastic sedimentary rocks are made up of pieces (clasts) of pre-existing rocks. (Bio)chemical sedimentary rocks are an inorganic process in which living organisms extract chemical components from the water and use them to build shells and other body parts.

Question 4

List the four sediment properties, and what they indicate

Answer 4

1) Composition: the material the sediment rock is composed of will tell us where it came from

2) Grain size: because larger grain size implies higher energy, this provides information on the conditions of transportation of the sediment

3) Sorting: the range of grain size indicates the process that delivers these sediments

4) Rounding: The more rounded sedimentary rocks are, the longer the distance of transportation

Question 5

Classify sediment and clastic sedimentary rocks based on grain size

Answer 5

Sediment: gravel, mud, sand
Clastic sediments: sandstone, conglomerate, shale

Question 6

Give examples of how certain sedimentary structures are indicative of certain sedimentary environment

Answer 6

1) Glaciers: picks up large and small pieces of sediments = poorly sorted deposit

2) Dunes: sand can get eroded and moved downhill, once it passes the angle of repose the dune will move (lines in wall of dune show direction of wind moving)

3) Streams: because the river shifts laterally through time, what starts as one part of river becomes another

Question 7

Distinguish between weathering and erosion

Answer 7

Weathering: the breaking down of rocks through contact with Earth’s atmosphere, water, and biological organisms

Erosion: the removal of rocks from one location of the Earth’s crust to another

Question 8

List, and explain, different types of physical and chemical weathering

Answer 8

1) Physical:
a. Joints: Body of rock deep within Earth solidifies but under a lot of pressure, as rocks above is eroded away, deep rock is under less pressure; will want to expand, but is solid and brittle hence cracks/breaks form in rock allowing rocks to expand along those cracks = joints

b. Expansion/contraction fracturing: dramatic changing temperature creates sudden expansion/contraction = rock fracture

c. Frost wedging: when temperatures fluctuate between below freezing and above, water freezes into ice, acting as a natural wedge in little fractures, joints, expansion/contraction fractures, divots of two rocks

d. Biological: living things act as agents of physical weathering

2) Chemical:
a. Dissolution: natural, weak acid can dissolve certain minerals (calcite; soft materials) over time

b. Partial dissolution: in more complex rocks mixed with different mineral chemistries, the less chemically stable crystals will dissolve first, breaking down the outer parts of the interlocking grains of the rock which leads to the entire thing starting to fall apart

c. Oxidation: certain minerals (iron, steel) react with oxygen in the air, thus will “rust”; but nothing is being dissolved, but rather things are being “pulled out” and formed into new oxidized material

Question 9

List the different agents of erosion

Answer 9

Gravity (mass wasting), water (streams, oceans), glaciers (valley glaciers, continental glaciers), wind (ventifacts, dunes)

Question 10

Explain “angle of repose” and list some of the factors that influence it

Answer 10

The “angle of repose” is where matter comes to rest at the maximum angle/slope certain loose sediments can get

The more angular and bigger grain size of sediments create a greater angle, and a little bit of water can influence (too much can decrease it)

Question 11

Illustrate the difference between braided and meandering streams

Answer 11

(see iPad for drawing)
Meandering: muddier material, more vegetation, and gentler slopes; only one specific part of the river where energy is concentrated to “chip” away at the solid mud

Braided: Sandier/gravel-ly conditions, more desert, steeper slopes; multiple sources of energy

Question 12

Illustrate how a meandering stream evolves over time, and how it can produce an “oxbow” lake

Answer 12

(see iPad for drawing)
Water is pushed to the outside of a bend, and erodes the curve further, while water on the inside is slower and deposits sediment.

(see iPad for drawing)
Where the bends of two meanders meet, they bypass the curve of river, creating an oxbow lake which may then be infilled with overwash sediment.

Question 13

Illustrate how coastal erosion of a headland can cause the progression: sea cave → natural bridge → seastack

Answer 13

(see iPad for drawing)
Sea comes to chip away the sediments along the coast through waves which continuously “beat” away the cliffs; concentrated at bottom of cliff, waves erode away the softer parts first, caving/eroding in to create sea caves; overtime, creates bridge then eventually, water stretches bridges thin until it breaks into a seastack

Question 14

Explain how sand reaches beaches at deltas via rivers, is transported along the beach by longshore drift, and is eventually carried down submarine canyons to the deep ocean

Answer 14

River will take sediment down to the sea, but it slows and spreads out because water loses energy when it reaches the ocean (creating an alluvial fan shape). Longshore drift picks up sediment and pushes it up the beach at an angle, then takes it straight out (moving down beach). Eventually it will hit a canyon and get taken down to the deep sea

Question 15

Distinguish between two types of glaciers

Answer 15

1) Valley glaciers: originate in the high alpine, they flow through deep bedrock valleys that confine the ice on either side, and over time, they carve and U-shape these valleys

2) Continental glaciers: a continuous sheet of land ice that covers a very large area and moves outward in many directions.

*Continental glaciers are much larger, and they are less controlled by the landscape, tending to flow outward from their center of accumulation.

Question 16

Describe two ways glaciers can erode underlying rock

Answer 16

1) Abrasion: the process in which a glacier scrapes underlying rock (which can also show the direction glacier is moving: glacial striations); the sediments and rocks frozen in the ice at the bottom and sides of a glacier act like sandpaper, wearing away the rock

2) Plucking: the process by which rocks and other sediments freeze at the bottom of the glacier and are carried away by the flowing ice

Question 17

List common features that are deposited by glaciers

Answer 17

Moraines, eskers, drumlins (MED)

Question 18

Explain how wind can weather solid rock

Answer 18

By blowing bits of materials/small grain-sized sediments against cliffs and large rocks, this wears and breaks the rock down into sand and dust over time

Question 19

Outline the origin and nature of some natural hazards associated with each agent of erosion

Answer 19

1) Mass-wasting: landslides and avalanches; the movement of rock and soil down slope under the influence of gravity due to disturbances in the natural stability of a slope

2) Streams: flooding events, process of erosion chipping away bank/sediments

3) Oceans: cliffs being chipped away, coastlines shrinking; waves

4) Glaciers: glacier avalanches, glacial floods, glacial debris flows, glacier collapse, and glacier surges: slope failures and glacier detachments

5) Wind: sand storms, dust hazardous for health; increase wind speed

Question 20

Explain how weathering and erosion contribute to fertile soil

Answer 20

Weathering breaks down sediments that contain properties beneficial for soil in the rock, and erosion of that weathered rock can bring this broken down material, that forms the basis of that soil, to areas that it gets deposited

Question 21

Explain different reasons why metamorphisms can result in different types of metamorphic rocks

Answer 21

Rocks undergo metamorphism because of exposure to greater temperature, pressure, hot mineral-rich fluids or, more commonly, some combination of these factors. These conditions are found deep within Earth or where tectonic plates meet

Question 22

List different ways that rocks and minerals respond to metamorphism

Answer 22

1) Coarsening: recrystallization to larger, fewer, or coarser crystals

2) Strain: if pressure they are under is greatest in a particular direction, i.e. pushing down, they change their shape

3) Growth of new minerals: crystals can grow as minerals recrystallize into new minerals

4) Changing their identity: individual minerals change their specific identity without changing their composition or interacting with other minerals

Question 23

Distinguish between weather and climate

Answer 23

Weather: the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy

Climate: the long-term average of weather, typically averaged over a period of 30 years

Question 24

Explain how the greenhouse effect works, and why certain gasses are greenhouse gasses

Answer 24

Some of the infrared radiation from the Sun passes through the atmosphere, but most is absorbed and re-emitted in all directions by greenhouse gas molecules and clouds, warming the Earth’s surface and the lower atmosphere.

When the infrared rays hit a GHG molecule (water vapor, carbon dioxide, methane, nitrous oxide and ozone), the molecule becomes charged. It then starts vibrating, creating adjacent gas molecules of any kind to vibrate as well which “traps” warming the atmosphere

Question 25

Distinguish between climate change caused by “climate forcing”, and that caused by positive feedback

Answer 25

“Climate forcing”: “Input-output” relationship where the change of one input directly affects the output

Positive feedback: the product of a reaction leads to an increase in that reaction

Question 26

Distinguish between positive and negative climate feedbacks, giving an example of each

Answer 26

Positive feedback: the product of a reaction leads to an increase in that reaction (e.g. when the surface temperature rises, melted ice and snow reveal ocean water, leading to an increase in the solar radiation absorbed by the surface (hence more land and water is revealed, further lowering Earth’s albedo which further accelerates melting), leading to an enhanced surface warming)

Negative feedback: self-stabilizing loop, the output of feedback is input back into the process when the company makes changes (e.g. as greenhouse gasses increase in atmosphere, plants grow faster)

Question 27

Explain how melting of sea ice represents a positive feedback for global warming

Answer 27

When the surface temperature rises, melted ice and snow reveal ocean water, leading to an increase in the solar radiation absorbed by the surface (hence more land and water is revealed, further lowering Earth’s albedo which further accelerates melting), leading to an enhanced surface warming

Question 28

Discuss the various ways (direct and indirect) that warming of the planet poses hazards to people and the environment

Answer 28

(direct)
Increase in heat waves, global temperature and carbon dioxide, disasters (floods, storms, droughts, wildfires), significantly altering environmental ecosystems, moisture (greater evaporation creates greater precipitation, and vice versa)

(indirect)
Threat to biodiversity, death and illness from increasingly frequent extreme weather events, food shortages, loss of homes, etc

Question 29

State the amount of sea level rise expected by the end of the century, and some of the impacts that this will (and is already) having

Answer 29

About 2 feet. Impacts include from increased intensity of storm surges, flooding, and damage to coastal areas to islands and land disappearing

Question 30

Explain how geology can be applied to trap and store carbon dioxide, keeping it out of/removing it from the atmosphere

Answer 30

Through carbon sequestration, the process of storing carbon dioxide in underground geologic formations, the CO2 can be pressurized until it becomes a liquid, and then it is injected into porous rock formations in geologic basins

Question 31

Explain the difference between absolute and relative ages

Answer 31

Relative age is the age of a rock layer (or the fossils it contains) compared to other layers

Absolute age is the numeric age of a layer of rocks or fossils

Question 32

Determine the relative ages of geologic units using the six principles of relative dating

Answer 32

1) The Principle of Superposition: the oldest layers are on the bottom

2) The Principle of Original Horizontally: due to the influence of gravity, all sediment is originally deposited horizontally

3) The Principle of Lateral Continuity: similar layers of rock that are separated by an erosional feature were once continuous

4) The Principle of Cross-Cutting: any geological feature that crosses other layers or rock must be younger than the material it cuts across

5) The Principle of Inclusions: an inclusion within some material must be older than the material it is included in

6) The Principle of Faunal/Fossil Succession: sedimentary rock strata that contain fossils succeed each other vertically in a specific, reliable order that can be identified over wide horizontal distances (basically matching fossils to same fossils in another rock)

Question 33

Draft a set of annotated diagrams illustrated the geometries and age relationships for the three types of unconformities

Answer 33

(see iPad for drawing)
1) Disconformity: Older and younger layers are parallel, no angular different between top and bottom

2) Angular unconformity: Older layers are tilted, and then newer layers are deposited

3) Nonconformity: not as defined, you can see layers on the top, but not on the bottom

Question 34

Explain the principles behind radiometric dating

Answer 34

Uses the rate of decay of a radioactive isotope to time how much time has elapsed since something crystallized/formed/cooled

Logic:
The atoms of some chemical elements have different forms (isotopes), however, the nucleus of these chemical elements are unstable; thus these isotopes (the parent) release radiation to attain stability by breaking down (radioactive decay) and forming a new isotope (the daughter) over time (radioactive isotopes); each radioactive element decays at a unique constant rate (half-life); by comparing comparing the proportion of parent and daughter isotopes to rocks now + its known half-life, you can calculate the age of the rock

Question 35

List three other methods of absolute dating

Answer 35

1) Fossil dating: uses the age of fossil to constrain the age of a rock containing that fossil

2) Magnetic dating: uses the known pattern of magnetic pole movement to determine the ages along a stratigraphic section

3) Counting annual layers: counting the rock/tree/ice layers

Question 36

Explain adaptive radiation, and its connection to mass extinction events

Answer 36

The diversification of a group of organisms into forms filling different ecological niches to adapt to different circumstances/environments. After a mass extinction, organisms that do survive because of their specific traits will continue to evolve (adaptive radiation) to the new circumstances/environments.

Question 37

Discuss why the fossil record is incomplete

Answer 37

Most organisms decomposed or were eaten by scavengers after death, most lacked hard parts which are more likely to be fossilized, and some rocks and the fossils they contained have eroded

Question 38

Give examples of how modern, living organisms can be used as analogs to better understand extinct, fossil organisms

Answer 38

If a fossil matches a modern organism’s physiology, scientists can conclude that the fossilized organism may have done a similar action

e.g. dinosaur with something that look like wings could have maybe flown, like a bat

e.g. trilobites had a hard exoskeleton made of multiple, overlapping plates, similar to rolly pollys

Question 39

State how fossil assemblages and trace fossils tell us something about how a fossil organism lived

Answer 39

Fossil Assemblages, the whole assortment of fossils in the same piece of rock, can reveal relative ages and window into life cycle

Trace Fossils, traces left behind by organism, show how organism walked or interacted with the environment (behavior)