Geology Midterm

Why do "new" minerals that did not exist in the "parent rock" form during metamorphism of a rock (e.g., garnet in schist)? Hint: T and P

"new" temp. and pressure conditions cause a change in the stability in the rock's minerals

Geology is considered a(an) _______ science, because ______.

"outdoor"; a great deal of geology is based on observations in the field

Precipitation occurs in 2 ways: 1. ____________ processes (evaporation) 2. ____________ processes (biochemical origin)

1. Inorganic processes (evaporation) 2. Organic Processes (biochemical origin)

Where slate would likely form:

A.

A hypothesis that passes a test is considered a fact. T/F

False

Current estimates suggest that Earth's core is composed primarily of __________.

Iron

What is geology?

Study of the earth

Mesosphere

The strong, lower part of the mantle between the asthenosphere and the outer core. (C)

Arkose

Type of sandstone containing at least 25% feldspar.

Viscosity

a liquid's resistance to flow

Relative dating involves __________. a) placing events in their proper sequence or order without knowing their numerical ages in years b) using the law of superposition to compare the ages of rock layers c) comparing fossils found in rock layers d) all of the above

d) all of the above

Which of these is required to "weather" a rock? a. exposure to wind b. exposure to Earth surface temperature changes c. exposure to rain d. all of these

d. all of these

transform plate boundary

forms where two plates slide past each other

Which are the four most important physical processes of mechanical weathering?

frost wedging, unloading expansion, thermal expansion, biological activity

________ is characterized by the segregation of light- and dark-colored minerals into thin layers or bands.

gneiss

Which mineral is easily chemically weathered by dissolution and why?

halite - water molecules are polarized and help break ionic bonds by disruption of attractive forces

_______ rocks form as magma cools.

igneous rocks

________ is typically formed by metamorphism of a sandstone.

quartzite

eroision

the process by which wind, water, ice, or gravity transport soil and sediment from one location to another

Which of these is the most complete list of the agents of metamorphism, the agents that drive metamorphic transformations in rocks? - Heat and pressure work together, but pressure is not important without high temperature. - Heat is the most fluid agent of metamorphism, where a rock can be affected by its ready application. - Heat provides the energy to drive chemical reactions that result in recrystallization. - Heat is similar to pressure since as depth increases, both temperature and pressure increase, causing metamorphism.

- Heat provides the energy to drive chemical reactions that result in recrystallization.

Why is quartz common in sediment and sedimentary rocks, but potassium feldspar is not? - Hydrolysis causes feldspar to alter to clay, but quartz resists hydrolysis reaction. - Dissolution of feldspar causes increased dissolution of clay and quartz. - Oxidation reduces quartz to clay, and clay is carried by water to where it reverts back to quartz at a later point. - Sulfuric acid dissolves feldspar, but not quartz, allowing quartz to be dissolved by plain water.

- Hydrolysis causes feldspar to alter to clay, but quartz resists hydrolysis reaction.

Graphite is identified in a particular schist. Which one of the following conclusions is justified? - The rock also contains diamonds; both are crystalline forms of the element carbon. - The schist formed from a quartz-rich, sedimentary limestone. - The graphite lubricated shearing movements along a fault, causing a schist to form. - The pre-metamorphic rock was a shale or mudstone containing organic matter.

- The pre-metamorphic rock was a shale or mudstone containing organic matter.

In which setting would regional metamorphism be most likely? - at shallow depths below an oceanic ridge or rift zone - at shallow depths along major transform faults in the continental crust - at great depths in the crust where two continents are colliding - at shallow depths beneath the seafloor where water pressures are immense

- at great depths in the crust where two continents are colliding

Which of the four important mechanical weathering processes is most important, and which is least important in producing sediment? - frost wedging, biological activity - biological activity, exfoliation - expansion, biological activity - wind, water

- frost wedging, biological activity

Which are the three mechanisms by which minerals develop a "preferred orientation"? - recrystallization, differential stress, rotation - rotation, trilobite, change in grain shape - rotation, recrystallization, change in grain shape - hydrochemical, hydrothermal, regional

- rotation, recrystallization, change in grain shape

What are the prerequisites for foliation to occur in metamorphic rocks?

1. Parent rock must be subjected to differential pressure. 2. Parent rock must have the appropriate composition to develop foliation. a. For sedimentary rocks, they must contain clays. b. For igneous rocks, they must contain micas (muscovite or biotite) or amphibole.

Why do geologists use texture & composition to name igneous rocks?

1. Texture tells us how and when the magma cools and solidifies. 2. Composition tells us how and where the magma originated. 3. Each rock is a unique combination of texture and composition.

Using the scientific method, it has been deduced that the Earth is ________ years old .

4.5 billion

Which of the following explains best the difference between a hypothesis and a theory?

A hypothesis is developed to explain observations, but a theory is a hypothesis that has passed a series of tests.

Outer core

A layer of molten iron and nickel that surrounds the inner core of Earth (B)

Rocks

A naturally formed aggregate, or mixture, of minerals; have varied chemical compositions

Minerals

A solid inorganic substance of natural occurrence.

glassy texture

A term used to describe the texture of certain igneous rocks, such as obsidian, that contain no crystals.

In the rock cycle, which rock type may be weathered to become sediment, and eventually sedimentary rock?

ALL rock types.

Which of the following best explains the principle of superposition?

All sedimentary deposits accumulate on top of older rock or sediment layers.

Only silicate minerals with ____________ in their compositions will form clay via hydrolysis.

Aluminum

What element occasionally substitutes for Si in the crystalline structure of silicate minerals?

Aluminum

porphyritic texture

An igneous rock texture in which large crystals are scattered on a background of much smaller crystals.

Andesite is more likely to form in the laccolith because it has a higher ________ content, therefore having higher viscosity.

Andesite is more likely to form in the laccolith because it has a higher silica content, therefore having higher viscosity.

Isotope

Atoms of the same element that have different numbers of neutrons

Which of the following accurately states the basic differences between the disciplines of physical and historical geology? A) Physical geology involves the study of rock strata, fossils and deposition in relation to plate movements in the geological past, whereas historical geology charts how and where the plates were moving in the past. B) Historical geology involves the study of rock strata, fossils and geologic events, utilizing the geologic time scale as a reference, whereas physical geology includes the study of how rocks form and of how erosion shapes the land surface. C) Physical geology is the study of fossils and sequences of rock strata, whereas historical geology is the study of how rocks and minerals were used in the past.

B) Historical geology involves the study of rock strata, fossils and geologic events, utilizing the geologic time scale as a reference, whereas physical geology includes the study of how rocks form and of how erosion shapes the land surface.

Which of the Earth systems includes all living things?

Biosphere

Where schist would likely form:

C.

Warm, humid climates promote ___________ weathering. Dry, arid climates promote ___________ weathering.

Chemical Physical

How is "confining pressure" different from "differential stress"?

Confining pressure: forces are applied equally in all directions Differential stress: forces are applied inequally

Where gneiss would likely form:

D.

Catastrophism is the idea that _______.

Earth's landscapes have been shaped by sudden worldwide disasters AND Earth's landscapes have been shaped suddenly by unknown forces not in operation today.

shale is a metamorphic rock formed from slate T/F

False. Slate is formed from shale

Which of the following is true about the Earth system? - If something is changed about one part, nothing happens to the other parts. - If something is changed about one part, all of the parts are affected. - If something does not change about a particular part, changes occur in each other part.

If something is changed about one part, all of the parts are affected. If something does not change about a particular part, changes occur in each other part.

________ rocks can be separated into extrusive and intrusive types.

Igneous rocks

Feldspar turns into a clay via hydrolysis because ____________?

It is unstable at earth conditions; clay is stable.

How does chemical weathering aid mechanical weathering?

It weakens cracks in rocks, allowing water to better infiltrate, thus enhancing frost wedging in the appropriate climate.

Limestone ------> Shale -----> Sandstone Deeper ------------------------------> Shallow

Limestone ---> Shale -----> Sandstone Deeper ------------> Shallow

Low viscosity = Low _________

Low viscosity = Low silica

A decrease in pressure __________ a rocks melting temperature

Lowers

Adding water __________ a rocks melting temperature

Lowers

How is a felsic magma different from a mafic magma in terms of viscosity?

Mafic magma is not viscous and will flow easily to the surface. Felsic magma is viscous and does not flow easily.

Secondary diagnostic properties

Magmatism, HCl reaction, taste

How does mechanical weathering aid chemical weathering?

Mechanical weathering increases surface area for chemical attack.

Which process involves the solid-state changing of a rock into a new rock?

Metamorphism

What platy minerals form parallel mineral patterns, a schistosity, in typical schist?

Micas

________ is thought to form by partial melting and in situ crystallization of the melted portion.

Migmatite

Why would a ballooning Earth population be an issue for geologists?

Natural resources include minerals, and as demand increases, supply diminishes, and eventually is exhausted.

Which of the following best explains why there is a P-wave "shadow zone" between 105 and 140 degrees?

P waves are refracted crossing the mantle-outer core boundary.

crenulation cleavage develops when:

Rocks undergo more than one episode of regional metamorphism. Cleavage from first episode is folded and a second cleavage develops.

Conglomerate = ________ clasts Breccia = _________ clasts

Rounded, angular

What fact about seismic waves is used to interpret that the Earth's outer core is "liquid"?

S-waves do not travel through liquids

chemical sedimentary rock

Sedimentary rock that forms when minerals precipitate from a solution or settle from a suspension.

_______ rocks always form near the surface of the solid Earth.

Sedimentary rocks

Which best describes the formation of "hard water"?

Soluble ions from dissolution of minerals in rocks are retained in groundwater.

Primary Diagnostic Properties

Test individual minerals to determine crystal form, luster, color, streak, hardness, cleavage, and fracture

Weathering

The breaking down of rocks and other materials on the Earth's surface.

clasts

The broken pieces and fragments; larger grains

Which of the following is one of the most important fundamental discoveries about the Earth?

The earth is constantly changing

How do Earth's internal processes aid external processes like erosion?

The gradual elevation of Earth's surface by "mountain building" increases the slope of the land.

Why does the sill spread out more, while the laccolith swells more and forms a blister-like pouch?

The lava in the sill has low viscosity, therefore flowing more easily. The lava in the laccolith is more viscous and forms a blister-like pouch.

What is "talus" and which process of mechanical weathering is it most associated with?

The pile of rock pieces fallen off steep slopes after frost wedging.

Lithification

The process that converts sediments into solid rock by compaction or cementation.

How might one distinguish between a phyllite and schist texture?

The schist is relatively more shiny due to the relatively large size of its grains.

Asthenosphere

The soft layer of the mantle on which the lithosphere floats. (D)

What concept is used to explain why an increase in heat and pressure produces metamorphism?

This causes an increase in thermal energy so that chemical bonds between atoms are out of equilibrium and recrystallize.

regional metamorphism creates greater volume of rock than contact metamorphism T/F

True

Oxidation

Type of chemical weathering in which minerals combine with oxygen to form oxides, such as iron oxide with hematite. Water speeds up the process.

Unloading

Unloading is the removal of great weights of rock or ice that lie on the surface. This may happen through rising temperatures that melt ice sheets; erosion by wind, water or ice; or tectonic uplift. The process releases pressure on underlying rocks and causes them to expand upward and crack at the surface. As a result, greater areas of rock are exposed to mechanical and chemical weathering.

What is the relationship between volcanos and climate change?

Volcanic ash makes is cooler, as it blocks out the sun. Sulfur dioxide combines with water to form sulfuric acid rain. Both of these reflect sunlight, causing the temperature to drop.

How is weathering different from erosion?

Weathering produces sediment. Erosion transfers sediment from place to place.

Can any rock become any other rock?

Yes

Diagenesis

a collective term for all the chemical, physical, and biological changes that take place after sediments are deposited and during and after lithification

pyroclastic texture

a fragmental texture characteristic of igneous rocks composed of pyroclastic materials

Turbidites

a sediment or rock deposited by a turbidity current.

Sill

a tabular, concordant pluton

Dike

a tabular, discordant pluton

Aphantic

a type of fine grained igneous rock, the crystals in the rock can't be seen with the unaided eye

thermal expansion and contraction

a type of mechanical weathering in which the volume of rocks changes in response to heating and cooling

Why are weathering, mass wasting and erosion considered "external processes"? Select 2 a. These processes require external Earth conditions like wind, water and Sun to operate. b. These processes occur near that surface of the planet only, and are powered by internal processes. c. These processes involve the interaction of rocks and the Earth's internal processes. d. These processes occur at or near the surface of the planet only, and are powered by the Sun.

a) and d) a. These processes require external Earth conditions like wind, water and Sun to operate. d. These processes occur at or near the surface of the planet only, and are powered by the Sun.

Why do metamorphic changes occur at great depths? Choose 2 a. Greater depths are the locations of greater temperature and pressure necessary for metamorphism. b. Temperature increases with depth, causing rocks descending deeper to become progressively less stable and to metamorphose in response. c. Great depth is the area where most chemically active fluids are found, thus producing the most amount of hydrothermal metamorphism. d. Temperature decreases with depth, causing rocks descending deeper to become progressively less stable and to metamorphose in response.

a. and b. a. Greater depths are the locations of greater temperature and pressure necessary for metamorphism. b. Temperature increases with depth, causing rocks descending deeper to become progressively less stable and to metamorphose in response.

divergent plate boundary

an area beneath the ocean where tectonic plates move away from each other

Pluton

an intrusive igneous structure that results from the cooling and hardening of magma beneath the surface of Earth

Which of the following best describes a condition of contact metamorphism? a. Pressure is very high, the rock is deeply buried, and temperature is raised by the Earth's internal heat. b. Pressure is fairly low, the rock is in the upper part of the crust, and heat is supplied from a nearby magma body. c. Heat is generated by shearing and mechanical movements along breaks. d. Depth is fairly shallow, but temperature and pressure are so high that the rocks begin to partially melt.

b. Pressure is fairly low, the rock is in the upper part of the crust, and heat is supplied from a nearby magma body.

Under similar warm, moist climatic conditions, why would basalt and gabbro generally have higher chemical weathering rates than rhyolite and granite? a. The quartz in the gabbro and basalt decomposes very quickly. b. The ferromagnesian minerals in the gabbro and basalt are subject to oxidation and chemical breakdown. c. The plagioclase feldspars in the granite and rhyolite decompose readily to clay minerals and iron oxides. d. The potassium feldspars and quartz in the rhyolite and granite are more susceptible to cracking by frost wedging.

b. The ferromagnesian minerals in the gabbro and basalt are subject to oxidation and chemical breakdown.

Which of the following lists the minerals in order of rate of weathering, slowest to fastest? a. quartz, olivine, amphibole, potassium feldspar b. quartz, potassium feldspar, amphibole, olivine c. olivine, quartz, potassium feldspar, amphibole d. olivine, amphibole, potassium feldspar, quartz e. amphibole, potassium feldspar, quartz, olivine

b. quartz, potassium feldspar, amphibole, olivine

Why do rocks deep underground undergo exfoliation when they reach the surface?

because the pressure is taken off them, allowing them to expand (unloading)

massive

blobular-like

S waves (secondary waves)

body waves that travel through solids only (F)

Weathering is __________ of rocks at the surface of the Earth.

both the physical breakdown (disintegration) and chemical alteration (decomposition)

Mohorovicic discontinuity

boundary between crust and mantle (C)

Amphibolite is a foliated metamorphic rock composed principally of hornblende and plagioclase. How does it form?

by regional metamorphism of volcanic rocks such as basalt

Why do seismologists conclude that the Earth must be composed of distinct shells having varying properties? a) Seismic waves passing below the crust are instantly slowed down until they stop at about 200 kilometers depth. b) Seismic waves passing through the shallower parts of the Earth reflect off of the core. c) Seismic waves passing through the deeper parts of the Earth reflect or refract at distinct depths. d) Seismic waves passing through the deeper parts of the Earth change their type with depth.

c) Seismic waves passing through the deeper parts of the Earth reflect or refract at distinct depths.

Which of the following best describes "frost wedging"? a. A catastrophic breaking of rocks by the influx of water during hot periods of the day. b. A gradual process by which roots from trees wedge rocks apart as they grow larger. Once the rocks break and fall, new roots form in new cracks. c. A cyclic process by which water in fractures freezes at night, expanding the space between blocks of rock, followed by daytime ice melting. d. A momentary process by which water freezes inside the pore spaces in rocks, and explodes the rocks catastrophically.

c. A cyclic process by which water in fractures freezes at night, expanding the space between blocks of rock, followed by daytime ice melting.

Which of the following best describes a condition of fault-zone metamorphism? a. Pressure is very high, the rock is deeply buried, and temperature is raised by the Earth's internal heat. b. Depth is fairly shallow, but temperature and pressure are so high that the rocks begin to partially melt. c. Heat is generated by shearing and mechanical movements along breaks. d. Pressure is fairly low, the rock is in the upper part of the crust, and heat is supplied from a nearby magma body.

c. Heat is generated by shearing and mechanical movements along breaks.

Hutton's idea of Earth's uniformitarianism is that _______.

c. Physical, chemical and biological laws that operate today have also operated in the past

Which of the following best describes a condition of regional metamorphism? a. Heat is generated by shearing and mechanical movements along breaks. b. Depth is fairly shallow, but temperature and pressure are so high that the rocks begin to partially melt. c. Pressure is very high, the rock is deeply buried, and temperature is raised by the Earth's internal heat. d. Pressure is fairly low, the rock is in the upper part of the crust, and heat is supplied from a nearby magma body.

c. Pressure is very high, the rock is deeply buried, and temperature is raised by the Earth's internal heat.

Why is quartz, and rocks with lots of quartz in them, more resistant to weathering than olivine and rocks that have lots of olivine? a. Al-Si bonds are very weak, and quartz has very few of these bonds relative to olivine. b. Al-Si bonds are very strong, and quartz has a higher proportion of these bonds than olivine. c. Si-O bonds are very strong, and quartz has a higher proportion of these bonds than olivine. d. Si-O bonds are very weak, and quartz has very few of these bonds relative to olivine.

c. Si-O bonds are very strong, and quartz has a higher proportion of these bonds than olivine.

Which physical process is dominated by "root wedging"? a. expansion b. mass wasting c. biological activity d. frost wedging

c. biological activity

Why are "weathering" and "erosion" connected processes? a. No erosion without weathering into sediment b. No weathering without "exposed" surface from erosion of sediment c. both a. and b. d. neither a. nor b.

c. both a. and b. No erosion without weathering into sediment. No weathering without "exposed" surface from erosion of sediment.

What major change occurs during metamorphism of limestone to marble?

calcite grains recrystallize and grow large

The chemical weathering of aluminum-bearing silicate minerals frequently produces __________.

clay minerals

Phaneritic texture

coarse-grained, crystals are large enough to be seen w/out a microscope, formed by slow cooling (intrusive)

coal (anthracite) is different from other rocks because it is

composed of organic material

discordant

cuts across

In what ways do rocks become hotter, so that they can metamorphose? a. burial into the mantle, subduction, mid-ocean ridge proximity b. continental subduction, heating from magma cooling c. subduction, heating from magma cooling, diagenesis d. subduction, continental collision, heating from magma cooling

d. subduction, continental collision, heating from magma cooling

Glacial

deposited by ice

Eolian

deposited by wind

lee slope is the side of __________

deposition

the process that produced the texture of the metaconglomerate shown in the figure:

deposition in a river system - burial and lithification - imposed differential stress flattened and elongated the clasts

How are dikes and sills different? Similar?

different: shape + orientation of plutons similar: they are both tabular

In detrital sedimentary rocks the grain size is ___________ ______________ to the energy of the deposital environment

directly proportional High Energy = Large Grain Low Energy = Small Grain

The process of weathering is best described as the __________.

disintegration and decomposition of a rock on the surface of Earth

oceanic crust

earths crust located under the ocean (D)

Calcite resists thermal contraction because it has ______ bonds in its crystalline structure

elastic

Stoss slope is the side of ___________

erosion

Which type of mechanical weathering process is associated with "peeling like an onion," which is caused by ________?

exfoliation - unloading of rocks in response to progressive removal of rock from above

Why do rocks "weather"? a. Rocks expand upon heating, and root wedging deep below the surface promotes weathering. b. Rocks become subjected to much lower temperatures relative to the temperature at which the rock formed. c. Weathering is the response of rocks to changed environment from which it formed. d. Rocks spontaneously change into sediment and soil after erosion and exfoliation. e. A & B f. B & C g. All of the above

f. B & C b. Rocks become subjected to much lower temperatures relative to the temperature at which the rock formed. c. Weathering is the response of rocks to changed environment from which it formed

Hornfels

fine-grained (shales and siltstones) metamorphosed by contact metamorphism

xenolith

foreign rock

strata (beds):

layers of sedimentary rocks

What is interpreted as the "parent rock" of the metamorphic rock marble (the one that reacts with acid) and why?

limestone - it's composed of the mineral calcite exclusively, as is marble.

crust + rigid upper mantle =

lithosphere

volatiles cause rocks to melt at ________ ______________.

lower temperatures

_______ rocks form deep within the Earth's crust, and are "transformed" from other rocks.

metamorphic rocks

What is used to determine the composition of the Earth's core?

meteorites that contain large percentages of iron

Hydrolysis

mineral reacts with water or stronger acid, such as carbonic acid

In which climate is chemical weathering most effective?

moist areas with warm temperatures

matrix

mud or fine grain which surrounds the clast

transgressive =

nearshore (shallow) on top of offshore (deeper)

marine transgression

occurs when sea level rises with respect to the land, resulting in offshore facies overlying nearshore facies

regressive =

offshore (deeper) on top of nearshore (shallow)

concordant

parallel to layer of host rock

foliation is always ________________ to the force acting on the rock

perpendicular

Fluvial

pertaining to a river

What are the two branches of geology?

physical and historical

Sedimentary rock records the ______, _______, and _______ conditions at the time and place in which they form.

physical, chemical, and biological

Hydrolysis is the most efficient chemical weathering process that alters silicate minerals. Which is a typical hydrolysis reaction? - calcium feldspar --> quartz - potassium feldspar --> clay - quartz --> clay - sodium feldspar --> mica

potassium feldspar to clay

What allows us to categorize rocks into the three rock types: igneous, sedimentary and metamorphic?

process of formation

What are the most important factors controlling the rates of weathering?

rock characteristics and climate

Detrital Sedimentary Rocks

rocks that form from the accumulation of materials that originate and are transported as solid particles

______________ rocks form near or at the earths surface.

sedimentary

Most of our knowledge about Earth's interior comes from ________.

seismic waves

bedding planes:

separate strata (layers of sedimentary rocks)

sedimentary facies

sequence of rocks that form at the same time in different depositional environments

Phyllosilicates have a _________ structure.

sheet

tabular

sheet-like

What is the basic building block of silicate minerals?

silicon tetrahedron

Which is the rock that forms the best rock cleavage and why?

slate - the grains are so small and so well intergrown that the rock is very strong and breaks along planes of fine micas.

Bi-directional current means

symmetry

Igneous rocks are classified by

texture and composition

dissolution

the breaking up or dissolving of something into parts; disintegration

During metamorphism, what is the major effect of chemically active fluids?

the fluids aid in the movement of dissolved silicate constituents and facilitate growth of the mineral grains

magmatic differentiation

the formation of one or more secondary magmas from a single parent magma

Talus

the pile of rocks that accumulates at the base of a cliff, chute, or slope.

Lithosphere

the rigid outer part of the earth, consisting of the crust and upper mantle. (E)

spheroidal weathering

the rounding of rock due to more rapid weathering of corners and edges

Bowen's Reaction Series

the simplified pattern that illustrates the order in which minerals crystallize from cooling magma according to their chemical composition and melting point

Lithosphere

the solid, outer layer of the earth that consists of the crust and the rigid upper part of the mantle (B)

slaty cleavage

the type of foliation characteristic of slates in which parallel alignment allows rock to split easily into flat plates.

Asthenosphere

the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur. (E)

What is a P or S wave "shadow zone" on the opposite side of the Earth from an earthquake?

the zone in which seismic station seismographs do not receive P or S wave arrivals

P waves (Primary waves)

travel through liquids and solids, push and pull, faster, arrive first. (G)

Which one of the following is NOT one of Earth's main layers based on mechanical strength? asthenosphere mesosphere inner core troposphere lithosphere

troposphere

Oolitic limestone is most likely to form in what type of depositional environment?

warm, tropical, shoreline environments

What is by far the most important agent of chemical weathering and why?

water - it is a good solvent and carrier of acids.