Geology: Earth's Composition, Minerals, and Rock Formation

What is a metamorphic rock?

rocks that are composed of pre-existing rock materials that have been physically and chemically changed while in the solid state

What are the three main agents of change in the metamorphic process?

heat, pressure, and chemically active fluids.

What are the three main sources of water in metamorphism?

connate water, dehydration water, and magmatic steam

What are the names of the two foliated aphanitic metamorphic rocks?

phyllite and slate

What is the protolith of quartzite?

quartz sandstone

What is the mode of metamorphism associated with intrusion of an igneous pluton?

contact metamorphism

Where is the metamorphic aureole located in an impact metamorphic situation?

The aureole is the area directly below the impact crater, which is filled with broken rock material.

What is the origin of the piedmont in regional metamorphism?

the Piedmont is formed by regional metamorphism of an area on the seaward side of a mountain range formed by tectonic plate collision

What is the name of the highest grade metamorphic indicator mineral?

sillimanite

What is relative age determination?

the process of observation and reasoning that permits discovery of which geological feature is older than others

What is absolute age determination?

the process of measurement and reasoning that permits discovery of which geological feature, rock, mineral grain, or part of a mineral grain is older than others

What are the three principles of relative age determination?

superposition, cross cutting relationships, and inclusions

What are the two principles of initial characteristics?

initial horizontality and lateral continuity

What are two principles of stratigraphic succession?

Facies succession and fossil succession

What are the three types of unconformities?

Disconformity, Nonconformity, Angular Unconformity

What are the three principles of geological reasoning?

Acutalism, parsimony, and multiple working hypothesis.

Where are the two principles of absolute age bracketing?

age bracketing by superposition and age bracketing by cross cutting relationships

After three half lives, what percent of parent atoms remain in the original mineral crystal?

12.5 percent

In age bracketing by superposition, what is age information is given by the age determination of the lava flow under the lower sandstone bed?

Maximum age of the overlying sandstone bed and its contained fossils.

What is structural geology?

the study of the three-dimensional aspects of rock formations and structures like faults and folds in order to determine their geological history. structural geology usually involves making measurements and creating geological maps.

What is geological structure?

features within or between rock formations that indicate deformation such as breaking or folding of rock

What is a geological cross section and what is a geological map?

cross section - diagram that shows the distribution and attitude of geological formations and structures in a vertical section wherein the upper surface is usually the earths surface.

map - shows surface distribution of geological formations and structures in a given area.

What is a fracture and what is a fault?

A fracture is a planar geological feature where rock is broken but there is no movement. A fault is a planar geological feature where there is breakage and movement.

What is the direction of movement of the hanging wall in a reverse fault?

The rocks above the fault plane move up relative to the rocks below the fault plane

what is a simple fold?

A simple fold contains deformed rock and has an axis that always horizontal.

What is an anticline and what is a syncline?

An anticline is a simple fold with two limbs and the limbs dip away from one another. A syncline is a simple fold with two limbs and the limbs dip toward one another.

What is strike and what is dip direction?

Strike is the compass direction, relative to north, of the line of intersection between an imaginary horizontal plan and an inclined (or dipping) planar geologic feature.

Dip direction is the compass direction, perpendicular to strike, of the maximum inclination down from horizontal of the dipping planar geological feature.

If a rock layer has a dip direction of southwest, what must be the strike direction?

Northwest.

What is the OTY rule?

In a sequence of dipping layers that have not been overturned, the oldest layer always dips toward the youngest layer.

What is plate tectonics?

the study of the the rigid components of the outer layer of the Earth and specifically how that crust is subdivided into large plates that are constantly in motion.

what is the thickness, composition, and density of the earths mantle?

2700 km, peridontite, 3.4 to 4.4

How do we know the location of tectonic plate boundaries?

the distribution of earthquakes define plate boundaries.

What are the three geographic areas included in the Eurasian tectonic plate?

Europe Russia and Siberia

What are two examples of divergent plate boundaries?

Atlantic mid ocean ridge and the east pacific rise

What is a convergent or closing plate boundary?

At convergent plate boundaries, the two opposing plates are moving toward one another.

What is the Benioff zone?

A down-going earthquake zone caused by the breakup of a down-going crustal plate

What are three examples of the convergent scenario where ocean floor meets ocean floor?

Japan island arch and Japan trench, Aleutian island arc and Aleutian trench, phillipine island arc and phillipine trench

What are the defining features of a sliding or transform plate boundary?

deep crustal faults and related surface features including offset rivers and mountain ranges

what is a hot spot and where does hot spot magma come from

hot spots are local sites of profuse volcanic activity and high heat flow that is not associated with plate tectonic movement.

What is mass wasting?

Downslope movement of Earth materials due to gravity.

What is the main factor in determining the speed and frequency of mass movements?

steepness of slope or the slopes gradient

What are the two main components of slope stability?

Stick and slide components

What is the maximum angle of repose of loose, granular material like sand?

25 to 40 degrees

what is a slide and what is a flow

A slide is a mass movement of Earth materials as a single body or unit along a plane of detachment.

A flow is a mass movement of Earth materials as a series of layers in which the upper layers move progressively faster than those below.

What is a debris slide and how fast does it move?

A debris slide is the downslope movement of a sheet-like mass of coarse rock debris that detaches from bedrock or consolidated Earth materials below it.

What is creep and how fast does it move?

Creep is the downslope movement of Earth materials because of the continuous rearrangement of constituent particles within the moving surface layer. Moves at a few cm/year.

What is a mud flow and how fast does it move?

A mud flow is the downslope movement of Earth materials that are fine-grained (clay and silt) and are water-saturated. Mud flows typically occur in channels that were formed previously by water flow. Moves rapidly (km/hr).

What is an avalanche and how fast does it move?

An avalanche is the sudden downslope movement of a mass of Earth materials, which have detached from their original location much like a slide, but instantly are pulverized and begin to flow rapidly. Moves rapidly (km/hr).

In mass movement mitigation, what is the purpose of a retaining wall with drains?

retaining walls help stabilize the sloping terrain, and drains in the wall to allow water flow out.

what is groundwater?

water stored under the earths surface mainly in porosity of soul, sediment, and rocks.

What is the water table?

line of contact between vadose and phreatic zones

what is an aquifer

a layer of soil, sediment, or rock that is capable of storing and discharging significant amounts of water.

What is permeability?

total amount of interconnectedness of open spaces in the soil, sediment, or rock.

What is the chemical equation for the acidification of groundwater?

H2O + CO2 = carbonic acid H2CO3

What is a gaining or effluent stream?

A gaining or effluent stream has an associated stream valley that is at or below the local water table, thus allowing ground water to seep into the flow of the stream.

What is the rule of groundwater motion with respect to water-table contour lines?

groundwater tends to flow perpendicular to water table contour lines.

What is a confined and what is an unconfined aquifer?

confined - aquifer with aquitards above and below itself

unconfined - aquifer with an aquitard below the aquifer.

What is a flowing or artesian well?

An artesian well is a well in which the main characteristic is water that rises above the level of the ground, and thus can easily flow outward from the well.

What is a connate water aquifer?

Connate-water aquifers typically lack a recharge area, therefore only a relatively small amount of water is available from this kind of aquifers.

What is a coastline?

a geographic boundary between the land and any body of water, such as a lake or ocean

What are the three present causes of global coastline change?

sea level rising, land level rising, coastal processes

What is a secondary coastline?

Secondary coastlines are shaped by the normal processes of marine erosion and deposition, including storm processes.

What is a glacial erosion coastline and how does one form?

formed by the movement of a mountain valley glacier.

What is a wave-erosion coastline and how does one form?

coastline formed by waves focusing on headlands.

What is longshore drift?

wind-wave drivers process of waved breaking on the shore face and then the water rushing back down the shore face toward the water body

What is a barrier island and how does one form?

A barrier island is a linear coastline that is not attached to the land, but instead there is a body of water between the barrier island and the mainland. Barrier islands form in one of three ways: lengthening spits; shoreward migration of offshore sand bars; or world-wide rise in sea level.

Where is a tombolo and how does one form?

Tombolos are formed by sand deposition where longshore drift is blocked (actually, wave energy is blocked), and thus sand piles up in the shadow of an offshore obstruction.

What is a key and how does one form?

The dead reefs form islands called keys.

What is the purpose of a breakwater?

A breakwater is a barrier to waves that causes sand deposition but also establishes a protected body of water for boat traffic and anchorage.