• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/69

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

69 Cards in this Set

  • Front
  • Back
Pre-existing rocks are broken down into smaller particles by
unloading
thermal expansion
frost wedging
In temperate and polar regions, the accumulation of talus slopes at the base of steep, rocky cliffs is most often attributes to
Frost wedging
The production of tabular slabs of rock caused by unloading of material overlying igneous bodies is known as
Sheeting
In the accumulation of particles in a talus slope, which of the following influences moves particles to their resting place
Gravity
Mechanical weathering is a significant factor in the breakdown of rocks. Which of the following factors enhances the effectiveness of further weathering as particles are created
increased surface area of the particles
The chemical weathering process known as oxidation would be most effective in the breakdown of
Pyroxenes
The chemical weathering process known as dissolution is most effective in the breakdown of which of the following minerals?
Calcite
During hydrolysis, ions and clay minerals are produced by the decomposition of
Feldspars
The Hawaiian Islands contain active volcanoes and are known for nutrient-rich soils and lush vegetation. What is the most powerful explanation for this
1)Abundant rainfall
2)Minerals in the volcanic rock produce clay minerals as weathering by products
3)volcanic rocks contain minerals susceptible to hydrolysis
Sand dunes are typically dominated by quartz grains and very little other mineral matter. Why does this selection occur?
Quartz is extremely resistant to all forms of chemical weathering.
The formation of sedimentary rock requires
Weathering and erosion of pre-existing rocks
Which agents is capable of moving sediment from the site of formation to the site of deposition?
ice, waves, wind, running water
What is an example of a sedimentary rock composed of solid masses of inter grown crystal?
rock salt
you find a sedimentary rock that has all its flat particles aligned in parallel. From this you can infer that
the particles have been compacted
Sedimentary rocks that exhibit the inter growth of crystal masses are generally formed by
chemical weathering
Which two minerals are most common in detrital sedimentary rocks
clay minerals and quartz
What is the most abundant chemical sedimentary rock in Earth's crust?
Limestone
Working in the field, you find a rock that contains rounded fragments that are greater than 2 mm in diameter. What would you call this rock?
conglomerate
The geologic laboratory where you work received a sample for analysis that is composed of calcite that includes many microscopic fossils of marine organisms and reacts with acid. What name would identify this rock?
Chalk
Sediments
Sediment:
Rock and mineral fragments.
Shells.
Mineral precipitates.
Cemented into rocks.
Earth’s external processes
Weathering – the physical breakdown and chemical alteration of rock at or near Earth’s surface
Physical - Mechanical breakage and disintegration.
Chemical - Decomposition by reaction with water.

Erosion – the physical removal of material by mobile agents such as water, wind, ice, or gravity
Jointing
Deep crustal rocks are hot and under high pressure.
At the surface, crustal rocks cool and expand.
Igneous plutons crack in onionlike “exfoliation” layers.
These layers break off as sheets that slide off of a pluton.
Chemical Weathering
Reaction with water disintegrates many minerals.
Maximized under warm and wet conditions.
Tropical weathering is intensive.
Turns rock into heavily decomposed material
Chemical weathering is virtually absent in deserts.Dissolution
Some minerals (halite, calcite) dissolve.
Hydrolysis
Water breaks cation bonds in silicate minerals. Yields…
Dissolved cations.
Alteration residues.
Clay minerals.
Iron oxides (rust).
Chemical Weathering
Oxidation
Rusting is a familiar example.Hydration
Absorption of water into a mineral structure.
Results in a volume increase (expansion).
Biological Weathering
Organisms often important chemical weathering agents.

Plant roots.
Fungi.
Lichens.
Bacteria.
Organic acids
attack minerals
Weathering Feedbacks
Weathering processes often work as a positive feedback.
Physical weathering speeds chemical weathering. How?
An increase in surface area accelerates chemical attack.
Chemical weakening increases surface area via breakage.
Soil
Soil is a combination of mineral and organic mater, water, and air
That portion of the regolith (rock and mineral fragments produced by weathering) that supports the growth of plantsFactors controlling soil formation
Parent material
Time
Climate (temperature and precipitation)
Plants and animals
Slope
The soil profile
Soil forming processes operate from the surface downward
Vertical differences are called horizons – zones or layers of soil
The process of compaction, cementation and hardening of these sediments is termed
lithification
Sedimentary Rocks
Sediments are the building blocks of sedimentary rocks.
Sediments are diverse, as are the rocks made from them.
4 classes:
Clastic – Made from weathered rock fragments (clasts).
Biochemical – Cemented shells of organisms.
Organic – The carbon-rich remains of plants.
Chemical – Minerals that crystallize directly from water
Clastic Sedimentary Rocks
Clastic sedimentary rocks reflect several processes.
Weathering – Generation of detritus via rock disintegration.
Erosion – Removal of sediment grains from rock.
Transportation – Dispersal by wind, water, and ice.
Deposition – Accumulation after transport stops.
Lithification – Transformation into solid rock.
Clastic Sedimentary Rocks
Lithification – Transforms loose sediment into solid rock.
Burial – More sediment is added onto a previous layer.
Compaction – Overburden weight reduces pore space.

Clast (grain) size – The average diameter of clasts.
Range from very coarse to very fine.
With increasing transport, average grain size decreases.
Clastic Sedimentary Rocks
Angularity and sphericity – Indicate degree of transport.
Grain roundness and sphericity increases with transport.
Well-rounded – Long transport distances.
Angular – Negligible transport.
Clastic Sedimentary Rocks
Sorting – The uniformity of grain size.
Well-sorted – Uniform grain size.
Poorly sorted – Wide variety of grain sizes.
Biochemical and Organic Rocks
These are sediments derived from living organisms.
Biochemical limestone – Made from CaCO3 shell remains.
Carbonate grains accumulate in the “carbonate factory.”
Warm (tropical and subtropical).
Normal-salinity marine water.
Oxygenated.
Shallow.
Clear.
Biochemical and Organic Rocks
Organic rocks – Made from organic carbon.
Coal – Altered remains of fossil vegetation.
Accumulates in lush tropical wetland settings.
Requires deposition in the absence of oxygenComprised of minerals precipitated from water solution.
Evaporites – Created from evaporated seawater.
Evaporation triggers deposition of chemical precipitates.
Examples include halite (rock salt) and gypsum.
Sedimentary structures
Large scale features of sedimentary rocks
Generated by a variety of processes and reflect environmental conditions
Occur at very different scales, from less than a mm (thin section) to 100s–1000s of meters (large outcrops);
Microforms (e.g., ripples)
Mesoforms (e.g., dunes)
Macroforms (e.g., bars)
Bedding and lamination
Sedimentary rocks generally have bedding or stratification
Graded Bedding
Some beds show an upward gradual decrease in grain size, known as graded bedding
Bedforms
Small-scale alternating ridges and troughs
Current ripple marks
water or wind currents flowing in one direction
asymmetric profiles
Wave-formed ripple marks
result from the to-and-fro motion of waves
symmetrical
Current Ripple Marks
The internal structure shows small-scale cross-beddingCan tell you the direction and strength of the current by the size of the ripple, you will find asymmetric ripples for example such as beach side, or sand dunes, because the wind direction is always changing and the strength of the winds may also change to create an asymmetric profile.
Wave-Formed Ripples
Ripples are More Symmetrical because the waves move back and forth to create the ripples…
Mud Cracks
When clay-rich sediments dry, they shrink and crack into polygonal patterns bounded by fractures called mud cracksalong a lakeshore
or a river flood plain
or where mud is exposed at low tide along a seashore
Biogenic Sedimentary Structures
Biogenic sedimentary structures include
tracks
burrows
trails
Extensive burrowing by organisms is called bioturbation
Bioturbation
U-shaped burrows
Vertical burrows
What are metamorphic rocks?
“morphos” is Greek for form“meta” is Greek for changemetamorphism means
“change of form”
Introduction
Protoliths (parent rock) undergo pronounced changes in…
Texture.
Mineralogy.
Due to change in physical or chemical conditions.
Burial.
Tectonic stresses.
Heating by magma.
Metamorphism
Metamorphism occurs in the solid state.
It doesn’t include weathering and melting.
Metamorphics often look totally unlike protoliths.
Metamorphic Character
Metamorphic rocks have distinctive properties.
Unique minerals – Some that are only metamorphic.
Staurolite, Kyanite, Sillimanite, etc.
Unique foliation – A planar fabric from aligned minerals.
Agents of Metamorphosis
Three primary “agents” can metamorphose rock
Heat (Temperature – T).
Pressure (P).
Differential stress.
Hydrothermal fluids (chemically activeby changing the chemistry, mineralogy, and/or structure of the rocks, without melting them
Heat (Temperature)
Metamorphism occurs as the result of heat.
Temperature (T) ranges between 200oC and 850oC.
The upper T limit is…melting. It varies based upon rock mineral composition and water content.

Sources of heat.
The geothermal gradient.
Magmatic intrusions.
Compression.
Pressure (P)
P increases with depth in the crust.
270 to 300 bars per km.
Metamorphism occurs mostly in 2 to 12 kbar range.
T and P both change with depth.
Mineral stability is highly dependent upon T and P.
This stability can be graphed on a “phase diagram.”
Changes in T and P lead
to changes in minerals
Differential Stress
Pressure that is greater in one orientation.
A commonplace result of tectonic forces.
Hydrothermal Fluids
Hot water with dissolved ions and volatiles.
Hydrothermal fluids facilitate metamorphism.
Accelerate chemical reactions.
Alter rocks by adding or subtracting elements.
Hydrothermal alteration is called metasomatism.
Types of Foliated Rocks
Slate – low grade change from shale
Schist = high grade change from shale

Gneiss = high grade change from shale/sandstone or granite/rhyolite
Non-foliated Rocks
Don't have planes, have no preferred orientation, not subjected to any directed pressure
Determining geological ages
Relative age dates – placing rocks and events in their proper sequence of formation
Numerical dates – specifying the actual number of years that have passed since an event occurred (known as absolute age dating)
Principles of relative dating
Law of superposition
Developed by Nicolaus Steno in 1669
In an undeformed sequence of sedimentary rocks (or layered igneous rocks), the oldest rocks are on the bottom
Principles of relative dating
Principle of original horizontality
Layers of sediment are generally deposited in a horizontal position
Rock layers that are flat have not been disturbed
Principle of cross-cutting relationships
Younger features cut across older feature
Principles of relative dating
Inclusions
An inclusion is a piece of rock that is enclosed within another rock
Rock containing the inclusion is younger
Principles of relative dating
Unconformity
An unconformity is a break in the rock record produced by erosion and/or nondeposition of rock units
Absolute-Dating Methods
Radioactivity is the spontaneous decay of an atom’s nucleus to a more stable form
Radioactivity provides geologists with a powerful tool to measure absolute ages of rocks and past geologic events
Atoms: A Review
The nucleus of an atom is composed of
protons – particles with a positive electrical charge
neutrons – electrically neutral particles
with electrons – negatively charged particles – outside the nucleus
Isotopes: A Review
Atomic mass number
= number of protons + number of neutrons
The different forms of an element’s atoms with varying numbers of neutrons are called isotopes
Radioactive Decay
Some isotopes are unstable. They undergo radioactive decay, releasing particles and energy.
Radioactive decay is the process whereby an unstable atomic nucleus spontaneously transforms into an atomic nucleus of a different element
Half-Lives
The half-life of a radioactive isotope is the time it takes for one half of the atoms of the original unstable parent isotope to decay to atoms of a new more stable daughter isotopeThe length of half-lives can vary from less than one billionth of a second to 49 billion years!
Radioactive Decay
In radioactive decay, during each equal time unit (half-life), the proportion of parent atoms decreases by 1/2
Example:
If a rock has a parent/daughter ratio of 1:3
and the half-live is 57 million years,
how old is the rock
25% means it is 2 half-lives old.

the rock is 57my x 2 =114 million years old.
Determining Age
By measuring the parent/daughter ratio and knowing the half-life of the parent which has been determined in the laboratory geologists can calculate the age of a sample containing the radioactive element