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REVIEW for EXAM 2
ESCI 121
J Hemzacek
FINAL VERSION
additions/clarifications in red; deletions (not on the test) are struck through
Key concepts from covered topics are listed below. Learning objectives of the course are emphasized in what
you are expected to be able to define, describe, and explain. Important terms are in bold: you should focus on
the meaning and importance in context with related concepts. Note that in your reading, etc., you may have
encountered concepts that are not listed here: those will not be on the test – except: you should be able to
do the same types of things done in class.
Clarifications and additions in red; struck through means not on exam
Some concepts below will be covered and/or clarified in our remaining class sessions before the exam
You should be able to...
Describe the differences in mechanisms and products of:
mechanical (physical) weathering
vs.
chemical weathering
Describe the following processes, related to weathering and sediments:
oxidation
dissolution
Explain the nature, the origin, and role of weak acid in weathering (that is, in nature: carbonic acid)
Describe the effects of important factors on the rates and effects of weathering, including:
rock type (texture and composition), including chemical stability
climate: what conditions would tend to favor each type of weathering?
presence of acidic conditions
and time
What climate conditions would most favor chemical weathering? vs. physical weathering?
When considering resistance or susceptibility to weathering, be able to explain the role of mineral properties
(i.e., for the minerals that are present in a rock): chemical stability
Mohs hardness
Name and describe the three main types of rocks, including: process(es) by which each type is formed;
relationship of the processes to types of geologic environments in which rocks are formed; general
characteristics of each type as a result of the processes and environments in which they are formed:
igneous (intrusive vs. extrusive)
sedimentary (clastic vs. chemical)
metamorphic
(foliated vs. non-foliated)
describe and/or diagram the relationship of the different rock types to one another and to earth processes that is, how one rock can be transformed into a new rock, perhaps of a different type; the cycling of
solid earth materials (...yes, that would be the "rock cycle").
Be able to identify the influence of plate tectonics in these processes: e.g., uplift, deep burial
and the role of isostasy (and the nature of the asthenosphere) in these vertical movements
In addition to rock type, we see evidence of geologic conditions in effects such as folding and faulting.
What is a fold; what does it represent? Under what conditions (and environment) does folding occur?
How is a fault different than a fold, in terms of what we can interpret about the geologic conditions?
(various types of stresses can be applied: tension, compression, shear; what effects can result?)
What topographic and geologic evidence (i.e., on maps) might we see for folding and faulting?
Distinguish the general difference(s) between relative age vs. numerical age of rocks
How is the relative age of rock units represented in the legend of a geologic map?
Be able to examine a simple sequence (cross-section view) and interpret the order of events, including relative
age of rock units, folding, faulting, and times of erosion
Describe characteristics or features that would be expected in sedimentary rocks, relative to the processes
and environments in which they form;
describe the significance of each of the following in the sedimentary process:
weathering
transportation (by wind, waves, streams, glaciers) deposition
lithification
cement
fossils
clastic vs. chemical sediment
Describe/ recognize differences between, and the general characteristics of, clastic vs. chemical rocks,
relative to the processes responsible for their formation
Describe each of the following rock textures, tell what they reveal about how the rock was formed, and
recognize* their appearance in rocks:
clastic / detrital (*when coarse - i.e., sand or larger)
fossiliferous
Describe the significance of the following set of terms, in context: gravel
sand
silt
clay
In the context of how sedimentary rocks are formed, explain how texture and composition of sedimentary
rocks can reveal clues about the sedimentary environment represented, & how this is related to
processes of weathering, transportation, and deposition.
include explanation of why clastic sediments would be sorted vs. unsorted (by size)
Describe the general differences in the characteristics of sediments deposited by wind, streams, waves,
vs. ice (glacier)
The sequence of sediments in sedimentary environments that we explored, from the onshore area (e.g.,
river floodplain) to margin (beach), to shallow sea, to deep ocean (sand/ silt/ clay/ lime mud), create a rock
sequence of: (terrestrial siltstone or shale)* -> sandstone –>siltstone –>mudstone/shale –> limestone
Besides the type of sediment/rock, what other evidence in the rock would reveal its environment of formation?
That is, how would you tell the difference between shale formed in floodplain vs. shallow sea?
–> If a layer of sandstone has a layer of shale on top of it, consider what kinds of change(s) would have
happened, in order to cause that change in sediment deposition?
Describe/interpret the significance of a series of sedimentary layers: e.g., coarse (sand) at bottom, to finer
material (limestone) upward in the sequence OR from fine at bottom to coarser above, as evidence for
relative sea level changes (transgression, regression)
Briefly list some possible causes of sea level changes relative to the land, and
explain the role of isostasy in relative sea level changes
describe differences in causes of “true” sea level changes (i.e., amount of water, basin size)
and relative sea level changes, which can be due to both true changes and effects of isostasy
Describe the types of evidence that we can gather (either from actual mineral/ rock samples, or from maps) for
a material's resistance to weathering (how is slope affected by weathering resistance?)
• "All rocks are classified/ named on the basis of texture & composition"... What does this mean?
• describe ways that composition and texture of a rock influence resistance to weathering
• What is actually tested by acid reaction? Why is acid reaction a useful test only for certain, specific
rocks and minerals? What characteristic of rocks/minerals is related to their reaction?
Define differential weathering; explain its significance, and describe and recognize examples of its effects, as
well as explain how and why this would occur
You should be able to use the information found in common map elements, including:
• standard conventions that apply to maps (e.g., north is “up”, etc.)
• using a map scale, determine the distance between two points
• determine type of information on a map (e.g., geologic, topographic; raised relief, shaded relief)
Examine a topographic map in order to:
• determine contour interval (even if that part of the legend is missing)
• determine elevation of a specific point, whether it is located on a contour or between contours
• relationship of contour interval to relief of an area/ landform; determine relief of a feature.
• identify areas that are flat, steep, not steep; high vs. low elevation, based on map information
• distinguish and be able to describe** topographic aspects of landforms, including:
hill or mountain vs. ridge
valley vs. canyon
plateau
plain
**what are the parameters that we use to describe topography??
• determine the direction of stream flow, both from elevation and from just the shape of contours
Use map features other than contours (e,g., stream drainage patterns, or other map symbols/ labels) to
determine general topographic characteristics of an area, such as determining high vs. low areas.
e.g., Recognize how drainage patterns of streams are related to differences in topography:
radial (Mt. Rainier) vs. dendritic (“tree-like”) vs. right angle tributaries (Grand Canyon);
What are the different ways to tell, from examining a stream on any map, which way a stream is flowing?
how to tell where a stream starts? how to use shape of contour lines where they cross the stream?
(and how to use shape of contacts, in an area with flat sedimentary layers?)
Describe the conditions and agents of metamorphism, describe the general types of metamorphic changes in
rocks, and describe characteristics of metamorphic rocks, relative to the processes and agents of
metamorphism and the types of environments in which it would occur, using key concepts:
heat
confining pressure
directional pressure
fluids
contact metamorphism
regional metamorphism
protolith
recrystallization
foliation
physical deformation
ductile deformation
What are the differences between foliated and non-foliated metamorphic rocks?
Under what conditions can a foliated texture develop? Under what conditions would it not develop?
Given a metamorphic rock, be able to identify whether or not it is foliated
What is the significance of this rock sequence: slate –> phyllite –> schist –> gneiss
How does the type of foliation reveal metamorphic grade?
given two foliated rocks, be able to discuss how to tell higher vs. lower metamorphic grade
How would we be able to distinguish marble and quartizite – two non-foliated rocks? and why?
components: quartz (H=7; insoluble) vs. calcite (H=3; soluble)
Describe the kinds of environments in which metamorphic rocks can form and associate different types of
geotectonic environments with different metamorphic conditions, such as:
high temperature, low pressure (contact metamorphism)
vs.
high pressure, low temperature (regional metamorphism): why is it called this?
pressure: different effects of directional pressure vs. confining pressure
Give examples as to how the type of protolith, and intensity of metamorphic conditions (metamorphic grade),
affects the type of metamorphic rock produced
Identify the following in cross-section and in map view:
folds; plunging (tipped) folds: what causes folding, and why would a fold be “tipped”?
faults
flat/ horizontal sedimentary layers
contact metamorphic zone
unconformity
What topographic characteristics are expected in an area of folds/tipped folds (e.g., Pennsylvania)?
How does examination of folds, and of topography, reveal not only the type of stress, but also the direction?
Applying these concepts, what do we know about the geologic history of the eastern US?
How can you tell the difference between older topographic features (i.e., mountains), and younger ones?
How would isostasy play a role in the overall height of a mountain range - whether old or young?
By examining outcrop patterns on a geologic map, and correlating map information to the map legend, you
should be able to determine the geologic processes that have affected an area, including:
• what is the relative age of rock formations present (oldest vs. youngest?)
• recognize an area representing igneous activity: extrusive vs. intrusive rocks
• recognize an area of flat/ horizontal sedimentary layers exposed by stream erosion
• when horizontal sedimentary rock layers are present, be able to use shape of geologic contacts
(in the absence of contour lines) to determine direction of stream flow
• recognize an area of folded sedimentary / metamorphic layers
• You should be able to recognize common rock names, and to be able to associate the names with
the correct rock type represented (sedimentary; igneous–intrusive / extrusive; metamorphic):
granite
basalt
andesite
pumice
sandstone
siltstone
shale
limestone
gneiss
schist
slate
marble
quartzite
note that ‘meta-(anything)’ is metamorphic; the ‘anything’ refers to the protolith!
Be able to describe how rock texture and composition reveal information as to how/where the
rock formed, including the rocks listed above
• what type(s) of rocks are present, and what types of environments do they represent (ocean?
beach? volcano? converging continents? other?)
Describe why sedimentary rocks and volcanic rocks might exhibit a similar relationship between oldest/
youngest rocks in a sequence of layers, and why metamorphic and intrusive rocks would not be expected to
have the same pattern
Be able to identify, interpret, and explain the various patterns seen on geologic maps:
e.g., “blobs”; “maple leaf” (“antlers”, maybe?), “stripes” & “swirls”.
For each, what can we interpret about the geology, geologic processes, and topography of the area?
note that these descriptions of the patterns that we see are not the “geologic interpretations”!
Each of these patterns has a relationship to stream patterns on a map – i.e., also to topography!
From map information (including rock types and geologic structures), or from a description of geologic
characteristics of an areas, be able to:
• comment on possible tectonic processes responsible for the geologic characteristics of an area;
• tell what likely geotectonic environment is represented, and
• be able to explain/ justify your interpretation
Don’t forget these important concepts: divergent
isostasy
mountain-building
convergent
subduction
transform
Also: tectonic processes are responsible for uplift and burial, which are necessary for the
transformation from one rock type to another (as shown in the rock cycle)
Explain the concept of unconformity:
e.g., the “Great Unconformity” in the Grand Canyon allows us to interpret that the geologic record is
incomplete with respect to absolute time. How can an unconformity be created?
Given a simple cross-section (side view), be able to determine the relative age (order) of geologic events,
including:
deposition of sedimentary layers; changes in environment/ sea level changes;
folding; faulting; erosion;
intrusion of magma/ formation of intrusive igneous body; contact metamorphism
and be able to explain how the relationships in the cross-section reveal the relative age of events
The “big picture” – you should be able to discuss:
– why do continents and mid-ocean ridges (notably in the Atlantic Ocean) have the shapes that we see?
how are these shapes related to the history of plate tectonic activity?
– give examples of geologic/ geotectonic environments in which each of the three main types of rocks are
found, in which folding and faulting occur, and in which mountains are created
– what can we tell from the characteristics of the Appalachian Mountains, regarding their formation? (these
mountains are a series of ridges & valleys that trend NE-SW: what can we tell about geologic
processes and stresses?)
– how do characteristics of older mountains compare to those of younger mountains, and why?
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See related homework assignment; be sure to follow directions!