Physical Geology 2 Flashcards

Terms Definitions
Quartz Formula
No electrical Charge
Salt (ionic bonds)
fragmental textures 2-64mm
fine-grained, cooled at surface
provisional explanation for observations that is subject to continual testing, if well supported, becomes theory
Mechanical weathering-definition
1)Mechanical weathering:
physical forces break rock into smaller pieces without changing the rock's mineral composition
Four processes important to fragment rock:
1)Frost wedging
when water freezes, its volume expands about 9%. As a result, water freezing exerts an outward force
when water freezes in a crack in the rock, it expands and enlarges the opening
after many freeze-thaw cycles, the rock is broken into angular fragments
after many freeze-thaw cycles, the rock is broken into angular fragments
the rock fragments fall to the base of the cliff, forming a talus scope
2)Unloading resulting in expansion
when the igneous body is buried deep inside the earth, pressure exerted on it is high
when the layers above the igneous body are eroded, a great reduction in pressure occurs
the outer parts expand more than the rock below and thus separate from the rock below, forming sheets
continued weathering eventually causes the rock slabs to fall off, creating exfoliation domes
3)Thermal expansion
heating rock causes expansion, cooling causes contraction.
heated swelling and shrinking on minerals with different expansion rates may exert enough stress to cause mechanical weathering
4)Biological activity
(humans, animals, plants)
plant roots in search of nutrients grow into fractures. As the roots grow, they wedge the rock apart
directions of weak chemical bonding
Native elements
non-silicate minerals include (5):
Tactonic Orogeny
450-435 Ma: exotic terrain
holds petroleum in reservoir rock.
p wave
compressional [longitudinal] wave; rock particles vibrate parallel to the direction of wave propagation; fast wave - from 4 to 7 km per second; first [primary] wave to arrive at a seismic station.
an erosional surface separating younger strata from older rocks
electrically neutral particle in nucleus of atom
concentration of naturally occurring solid, liquid, or gaseous material in or on earth's crust in such form and amount that economic extraction of a commodity from the concentration is currently or potentially feasible
hardness of a knife blade
minerals found in crustal rocks
Plate boundaries
Convergent: Andes mt. pacific northwest
Divergent: mid ocean ridge
The origin of the Earth
Nebular hypothesis
Sediments can be transported by (4):
Shield Volcanoes
Basaltic (runny) lava, precambrian meta rocks
Glacier formation
Greenhouse--glacial retreat, sea level rises
Icehouse--glacial, drop in sea level
Glacial--sea level lowers
Interglacial--sea level rises
1) thinner beneath oceans than continents.
2) seismic P-waves travel at 7km/sec through basalt & gabbro & 7km/sec through oceanic crust; therefore oceanic crust is of basalt & gabbro - higher density.
3) seismic P-waves travel at 6km/sec through granite & gneiss & 6km/sec through continental crust; therefore continental crust is of granite & gneiss.
intermittent streams are uncommon in deserts.
lava dome
bulbous, steep-sided mountain formed by viscous magma moving upward through a volcanic conduit
demonstration of time equivalency of rock units in different areas
any of the egg-laying mammals, includes only the platypus and spiny anteater of the Australian region
mass wasting process involving the downslop movement of water-saturated soil
rock fragment carried some distance from its source by glacier and usually deposited on materials of different composition
magma chamber
cavity containing resevoirof magma within earth's upper mantle or lower crust
partial melting
magma composition that involves melting by going from cool to hot
Block Field
pile of rocks sharply angular
smooth surface like twisty braids in ropes, formed when high temp magma, high gas content, low viscosity
Which of the following dating methods is not based on annual layering?
Solid substance
minerals are solids within the temperature ranges normally experienced on the earth's surface
____ rocks contain the mineral remains of organisms, such as shells or mineral precipitates as a result of biologic processes. e.g., Limestone
Confined Aquifer
holds water, but impermeable layer above it (aquitard)
Echo Sounder
sonar [sound navigation and ranging]; gets topography of sea floor.
Mid-Oceanic Ridge
of basalt; shallow focus earthquakes; high heat flow; pillow basalts; rift valley.
transverse dunes have crests that are perpendicular to the direction of the wind.
Depth of earthquakes
A) shallow focus = 85%
geologic cross-sections
imaginary vertical cuts through the crust
aseismic ridge
ridge or broad plateaulike feature that lacks seismic activity, rising as high as 2 to 3 km above the surrounding seafloor
shear strength
resiting forces that help maintain slope's stability
natural levee
ridge of sandy alluvium deposited along margins of channel during floods
native element
mineral composed of a single element
name Alfred Wegener proposed for a supercontinent consisting of all earth's landmasses at the end of paleozoic era
degree to which all particles in sediment or sedimentary rock are about the same size
contact metamorphism
metamorphism of country rock adjacent to pluton
volcanic neck
erosional remnant of material that solidified in a volcanic pipe
body waves
waves that travel through earth's interior
water table
surface that separates zone of aeration from underlying zone of saturation
place where groundwater flows or seeps out of the ground, occurs where the water table intersects the ground surface
lava flow
what hazards are associated with shield volcanoes?
ability of one mineral to scratch another
Caldera (R/A usually)
collapsed composite cones, large circular depression greater than a mile across, formed by a composite cone collapsing, collapses in on an empty magma chamber, sometimes fills w/water, Ex= crater late- U.S. state?
Intrusive Volcanism
activity below the earths surface (subsurface)
Igneous Rock
Form when molten magma cool and solidifies.
Grow up from the floor of a cave
Relative dating
placing of events in their proper order without knowing their age in years.
____ is the physical picking up of rock particles by transporting agents (wind, water, ice, or gravity).
PT extinction
killed 90% of marine life (the worst)
Uplift & Block-Faulting Stage
compression stops bc subduction ceases; isostatic adjustment causes mountains to rise along normal faults.
passive continental margin
margin that consists of continental shelf, continental slope, and continental rise. they are not associated with plate boundaries and therefore experence little volcansim and few earthquakes - ch12
fault plane
more or less planar fracture surface along which rocks on opposite sides have moved relative to one another
medial moraine
moraine carried on the central surface of glacier, formed where the lateral moraines of two valley glaciers merge
sedimentary structure
any feature in sedimentary rock that formed at or shortly after the time of deposition
fluid activity
agent of metamorphism in which water and carbon dioxide promore metamorphism by increasing the rate of chemical reactions
fracture along which the rock on each side has moved in opposite directions
Mohorovici discontinuity (Moho)
boundary between earth's crust and mantle
volcanic island arc
curved chain of volcanic islands parallel to deep-sea trench where oceanic lithosphere is subducted, causing volcanism and the origin of volcanic islands
crystalline solid
solid in which constituent atoms are arranged in regular, three-dimensional framework
glacial ice
water in solid state within glacier, forms as snow partially melts and refreezes and compacts so that it is transformed first to firn
water-flux melting
melting that occurs when the addition of water decreases the melting temperature of hot rock (changes composition, leading to change in melting temperature)
Gases and hot water
outgassings, geysers, and hot springs
Igneous rocks
*Extrusive: form when magma erupts at the surface, rapidly cooling to fine ash or lava and developing tiny crystals.
*intrusive: crystallize when molten rock intrudes into unmelted rock masses in Earth's crust
*intrusive are coarser.
*low Si=darker; high Si=lighter
An example of a rock type that could be a good aquifer is:
Divergent plate boundaries
• Plates move away from each other
• New crust is created by upwelling mantle
• Mid-ocean spreading ridge or spreading centre, or continental rift
formed when molten rock (magma) cools and solidifies.
Igneous rx def:
Diverging Boundary Characteristics
1) Basalt
2) Salt
3) Reef Deposits - limestone
4) Marine sediments
5) Normal faultse
continental slope
the steep gradient that leads to the deep-ocean floor and marks the seaward edge of the continental shelf - ch12
geologic time scale
chart arranged so that the designation for the earliest interval of geologic time appears at the bottom followed upward by progressively more recent time designations
water well
well made by digging or drilling into the zone of saturation
Igneous activity at convergent plate boundaries
1)Oceanic plate-oceanic convergence (formation of Ocean Island Arc)
2)Continental plate-oceanic plate convergence (formation of Continental Volcanic Arc)
plateau basalts
layers of basalt flows that have built up to great thickness
shield volcano
type of volcano that is broad and gently sloping (2-10 degrees); composed of solidified lava flows; mafic composition
What is baseflow?
the flow of groundwater that maintains streamflow during dry periods
Discharge is constent.
Bonus. As a river flows towards the ocean it widens but stays the same depth. Which of the following is true about the behavior of the stream as the channel widens? Assume constant gradient and that no more water added.
Rich in silica and aluminum
Relatively low crystallization temperatures
Feldspars and quartz, also muscovite mica
Major constituents of continental crust
Usually lighter in color
Less dense than mafic minerals
Define Felsic or silicic minerals:
thermal expansion and contraction
type of mechanical weathering in which the volume of rocks changes in response to heating and cooling
In what tectonic environment do blueschists and eclogites form?
Blueschist Facies (very high pressures, relatively low temperatures)
Occurs within subduction zones
Metamorphosed basalt and shale contain blue amphiboles
Eclogite facies (extremely high pressures,moderate-high temperatures)
2 types of Basaltic Lava
Aa- highly vesicular (holes), angular shape, forms far away from vent (sharp)
Pahoehoe-smoothly twisted, ropey, forms near vent (very runny)
What class of mineral is most abundant in the Earth's crust?
Oxides and hydroxides.
It will erode less
How will a stream respond if its velocity decreases?
Composition varies widely
Generally a silica melt - made up of silicate minerals
what is the Composition of igneous rocks?
exclusive economic zone (eez)
area extending 371 km seaward from the coast of the United States and its possessions in which the United States claims rights to all resources
3 Major Processes By which Denudation Works
Weathering, Mass Wasting, and Erosion
What are the rock types?
*igneous: melting of rocks in hot, deep crust and upper mantle
*sedimentary: weathering and erosion of rocks exposed at surface
*metamorphic: rocks under high temperatures in deep crust and upper mantle
Silica content of ~ 50% (relatively low)
High concentrations of Fe, Mg, and Ca
High temperature molten magma
1000o to 1200oC
Major minerals- mostly dark in color
what are characteristics of Mafic magmas?
Spreading Center Volcanism (divergent plate boundaries
tapping from the mantle to the surface get runny lava
exs= shield volanoes
lava plains-Iceland
cinder cones
What are the two approaches to the dating of rocks?
Relative Dating and Absolute Dating
What (and explain) are the physical properties of minerals?
*hardness: determined by the strength of a mineral's chemical bonds
*cleavage: how a rock will slit away
Viscosity of a magma- what influences the viscosity?
Low viscosity (fluid): flow is easy (basalt flow)
High viscosity: flow is difficult
What influences the viscosity?
1)Composition (silica content)
The higher the temperature, the lower the viscosity
3)Amount of dissolved gases
When magma loses gases and volatiles (water) as it moves toward the surface, it become more viscous
Low viscosity: basalt
High viscosity: rhyolite
List the three actions a wave can have on land it comes into contact with
b.Transport sediment and rock brought to the ocean by rivers
c.Deposit sand and rock down the coastline
The nature of magma- magma consists of three components:
1) liquid
The liquid portion is called melt
It is composed of mobile ions
It consists of the 8 elements that are common (silicon, oxygen, aluminum, potassium, calcium, sodium, iron, magnesium)
2) solid
The solid portion are minerals that have crystallized from the melt
When a magma body cools, the size and number of crystals increase
3) gas
There are gaseous components (called volatiles) dissolves within the melt
For example: water vapor (H2O), carbon dioxide (CO2), sulfur dioxide (SO2)
Where are Mid- channel bars likely to occur? What kind of stream is likely to result? Where do you see these most often?
In streams having large sediment loads and greatly fluctuating discharges. A braided stream is likely to occur . These are likely to occur when large glaciers are drained
How do changes in base level form canyons?
The rapid change in the base level forces the stream to downcut
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