Geo Exam 2 All Homeworks

Quartz is not a good index mineral because

It is stable over a very wide range of temperatures and pressures

If a fault offsets a sequence of sedimentary rocks, what must be true about the fault?

It is younger than the rocks based on the principle of cross-cutting relationships

Define the principle of original horizontality

Layers of sediment, when first deposited, are fairly horizontal

Which mineral is responsible for the strong foliation in a schist?

Mica

Which of the four types of seismic waves are body waves?

P-waves and s-waves

Order the steps in neocrystallization

Protolith minerals are consumed by chemical reactions. Thin clay minerals begin to align. Clay grains flatten out and become parallel to one another. Small garnets appear.

Form of metamorphism occurring at a fault zone

dynamic

Foliation is an alignment of mineral grains ____________ to the direction of compression

perpendicular

A vertical exaggeration of 1.00x on a topographic profile means

the vertical scale of the profile is 100x that of the map scale

The agents that cause metamorphism include all except which of the following?

Time

The low seismic velocity zone is caused by

a change in the rigidity of the mantle in the asthenosphere

The two main types of sedimentary rocks are

clastic and chemical

Attributes of crustal deformation being associated with folding

compressional stress, bending of geologic materials, and ductile deformation

A sedimentary rock with large class sizes (>2mm) would be called a

conglomerate

Consequences of shear stress

elongation of grains; foliation

Chemical weathering is highest in

rocks that have been broken up by intense physical weathering

A disconformity occurs when

there has been some uplift and erosion but no folding between deposition of rocks above and below the disconformity

Which of the four types of seismic waves are surface waves?

R-waves and L-waves

Marble is metamorphic rock that was originally

Limestone

Which property of a protolith may change during metamorphism?

Grain size, grain shape, and mineralogy

To show topography in a rugged, mountainous area, the most appropriate contour interval would be

100 feet

The absence of preferred orientation of minerals in a metamorphic rock may be due to what?

The lack of stress during metamorphism, the absence of play minerals like mica, and the absence of rod-shaped minerals like amphibole

Metamorphic index minerals help geologists determine

The temperature and pressure conditions during metamorphism

The asthenosphere is known from

a low velocity zone in the upper mantle

Contour lines on a map connect points

of equal elevation

What is one difference between body and surface waves?

Body waves are described as compressional or shear.

The principle of superposition can be used to determine the relative ages of all of these

a sequence of lava flows, layers of unconsolidated sediment in a lake, and horizontal layers of sedimentary rock inter-layered with lava flows

Which of the following is NOT an example of a chemical sedimentary rock

breccia

Attributes of crustal deformation being associated with faulting

brittle deformation

Form of metamorphism occurring ten miles below the surface

burial

Small tick marks (hachures) on contour lines indicate

depressions

Which of the following processes is NOT important in generating the components necessary for the formation of sedimentary rocks

diagenesis

Compared to the average density of the mantle, the average density of the continental crust is

less

What tectonic processes are associated with earthquakes?

plate subduction, mountain building, formation of ocean basins, and movement along plate boundaries

The zero contour line is also known as

sea level

Long-term earthquake predictions are based on what?

seismic belts and recurrence intervals

Form of metamorphism occurring at a meteorite impact site

shock

Particle size is used as an indicator of maturity in clastic rocks. This is because

smaller particles have been transported farther and are therefore older

Glacial isostatic rebound refers to

the isostatic uplift of continental margins associated with meltwater induced sea level changes since the glacial maximum

The Moho is

the observation that seismic waves speed up below the crust mantle boundary in association with a compositional change

The face that the outer core is liquid is known from

the s-wave shadow

An angular unconformity is evidence that

there is an incomplete geologic record preserved in an area

Form of metamorphism occurring at a intrusion of a pluton

thermal

In order for a fossil to be used as an index fossil, the species must have existed for a

very short span of geologic time and lived throughout the world

The term relative age refers to

whether a feature is older or younger than another

What does the assemblage of minerals in a metamorphic rock help to determine?

The chemical composition of a protolith, the temperature at which metamorphism took place, and the pressure at which metamorphism took place.

What does the term metamorphic grade refer to?

The degree to which a metamorphic rock's protolith has changed

Foliation and lineation are terms that describe

The orientation of minerals in metamorphic rocks

What solid is most likely to deform elastically under stress?

a rubber band

The principle of inclusions states that

a sedimentary rock must be younger than the clasts that it contains

Which statement best agrees with the isostasy model of G.H. Pratt?

High elevation regions have lower-density crust than lower elevation areas.

Which statement best agrees with the Airy model for isostacy?

High topography regions have thicker crust than lower relief areas

Contours form closed loops around

depressions and hills

The two types of chemical sedimentary rocks are

inorganic, biochemical

To show topography in a flat coastal area, the most appropriate contour interval would be

5 feet

How is ductile deformation different from elastic deformation?

Ductile deformation ca result in tight folds, whereas elastic deformation usually terminates in brittle deformation rather than tight folding. Once the stress is removed, rocks that have undergone ductile deformation retain their new shape.

What types of deformation do rocks undergo during formation of an orogenic belt such as the Alps?

Faulting, folding, foliation, and jointing

What is true about earthquakes?

Most are the consequence of plate tectonics, an estimated 1 million occur each year, but most are small, and most occur along plate boundaries

Imagine a mountain range supported by a low-density root zone (Airy's hypothesis). What is the isostatic response as rivers erode the mountain away?

The mountains and root zone rise, and the mountains become lower as the root zone also diminishes.

A Wadati-Benioff zone is

a band of earthquakes along subducting lithosphere in a convergent boundary

A benchmark is

a permanent marker on the ground that indicates location and elevation

What is isostasy?

a state of gravitational equilibrium maintained by a block of lithosphere that "floats" in the underlying mantle at a level determined by both its density and its thickness

Consequences of uniform pressure

development of large, equant grains; rounding of grains

Form of metamorphism occurring at a mountain range core

dynamo-thermal

The Moho and the base of the lithosphere are the same

false

Immature sedimentary rocks can be distinguished from mature ones by greater amounts of

feldspar

Form of metamorphism occurring at a mid-ocean ridge

hydrothermal

Information on the borders of a topographic map includes all except

the types of rocks present in the map area

What type of unconformity forms when sedimentary rocks overlie either igneous or metamorphic rocks?

a nonconformity