Geology exam 2 "review"
What is the primary basis for distinguishing among detrital rocks?
particle size
Which of the choices below is not weathering by biological activity?
salt crystal growth within rock fractures
Distinguish among a conduit, a vent, and a crater.
A conduit is the circular path through which magma ascends to the vent, which is the surface opening of the conduit. A crater is a funnel-shaped depression around the vent.
Which of the following statements correctly describes a parasitic cone?
A parasitic cone is a small cone on the side or base of a volcano that has formed during repeated flank eruptions.
How do the crystallization and settling of the earliest formed minerals affect the composition of the remaining magma?
After the earliest formed minerals have settled, the resulting magma will be more felsic than the original magma.
Aa lava flow
Angular, jagged, blocky, more viscous lava flow.
Choose the statement that describes two processes that alter the composition of magma.
Assimilation occurs when magma that is injected into bedrock melts the rock directly surrounding it, incorporating it into the magma, whereas magma mixing occurs when two ascending bodies of magma join and mix together into a composition that is intermediate to the two original magmas.
How is carbonic acid formed in nature?
Atmospheric carbon dioxide dissolves in raindrops.
Why does partial melting result in a magma having a composition different from the rock from which it was derived?
Because different minerals melt at different temperatures, minerals that melt at lower temperatures will melt first, creating a magma that has a more felsic composition than the parent rock from which it formed.
How do craters differ from calderas?
Calderas, which have diameters of 1 km or more, are much larger than craters.
How are chemical rocks identified
Chemical rocks are primarily identified based on their compositions
Which of the following statements accurately describes the composition of a cinder cone?
Cinder cones are composed of generally basaltic pyroclastic material and scoria.
Over what time span do most typical cinder cones form?
Cinder cones are generally the product of a single eruption and thus are constructed in less than a year or less than a month.
Why are coal, oil, and natural gas called "fossil fuels"?
Coal is made from fossil plant matter, and oil and natural gas are made from fossil plant matter and fossil marine animal matter.
How do the eruptions that created the Columbia Plateau differ from eruptions that create large composite volcanoes?
Eruptions that created the Columbia Plateau ejected basaltic magma from fissures; eruptions that create large composite volcanoes eject silica-rich lava from vents.
What is the difference between extrusive igneous rocks and intrusive igneous rocks?
Extrusive igneous rocks cool and solidify on the Earth's surface, whereas intrusive igneous rocks cool and solidify beneath the Earth's surface
Which of the following choices correctly classifies the four listed igneous rocks by composition?
Gabbro is mafic; obsidian is felsic; granite is felsic; andesite is intermediate.
How have human activities affected the rate of soil erosion?
Humans have increased the rate of soil erosion by removing vegetation through activities such as farming, logging, and construction.
In what situation is hydraulic fracturing used?
Hydraulic fracturing is used to open cracks in impermeable rocks so that the natural gas can flow into wells.
How do joints in rock promote weathering?
Joints allow water to penetrate the rock at depth and begin the weathering process.
How does magma differ from lava?
Magma exists strictly below Earth's surface, whereas lava is found on Earth's surface.
How do lava tubes form?
Pahoehoe flows develop cave-like tunnels that were previously used for carrying lava from an active vent to the flow's leading edge.
____ are minerals typically found in igneous rocks that have a high silica content, whereas ____ are minerals that are typically found in igneous rocks with a low silica content.
Plagioclase, feldspar, and quartz; pyroxene and olivine
What is the raw material for coal, and how does it accumulate?
Plants are the raw material for coal; to form coal, plants must accumulate in oxygen deficient swamp water.
Why might a single rock layer exhibit different types of sedimentary rocks within it?
Such a rock layer, termed a facies, when traced laterally represents a variety of depositional environments that formed at the same time across a broad area.
How does the May 18, 1980, eruption of Mount St. Helens compare to a typical eruption of Hawaii's Kilauea volcano?
The Mount St. Helens eruption was more explosive than a typical eruption of the Kilauea volcano; The Mount St. Helens eruption destroyed a significant portion of the top of the volcano, whereas a typical eruption from the Kilauea volcano does not destroy the top of the volcano.
Which of the examples below shows how carbon moves from the geosphere directly to the atmosphere?
The burning of fossil fuels (e.g., coal) releases carbon dioxide directly into the atmosphere.
Which of the processes listed below would transform an exposure of granite in the mountains into sedimentary rocks?
The granite would mechanically weather into small particles, which would travel down the slope of the mountain by mass movement, be deposited, and undergo diagenesis when the sediments are buried under younger layers of rock.
batholiths
The largest of all igneous intrusions
What occurs when carbonic acid reacts with calcite-rich bedrocks such as limestone?
The limestone is dissolved and carried away by water.
How is magma generated along convergent plate boundaries?
The subducting plate drives water and carbon dioxide into the mantle, which reduces the temperature at which it melts, allowing mantle rock to melt and rise
How are the volcanoes in the Ring of Fire generally described?
They have violent eruptions, because most of these volcanoes are composite cones which eject andesitic lava.
How do volcanic bombs differ from blocks of pyroclastic debris?
Volcanic blocks are made of hardened lava, whereas volcanic bombs are made of incandescent lava.
volcanism at divergent plate boundaries is most often associated with which rock type
Volcanism at divergent boundaries is most often associated with basaltic rock
How can an angular mass of rock become a spherical boulder?
Water enters joints in the rock, where it preferentially weathers the corners and edges of the rock into a roughly spherical shape.
How can water cause mechanical weathering?
When water within fractures in a rock freezes, it expands, which applies pressure to the portions of rock immediately around it. This pressure breaks off pieces of the rock.
Are pyroclastic materials a significant component of shield volcanoes?
Yes; pyroclastic materials are more commonly ejected during the final stage of growth of a shield volcano, when eruptions become more sporadic.
Lahar
a mudflow of volcanic debris saturated with water
Pumice
a very light and porous volcanic rock formed when a gas-rich froth of glassy lava solidifies rapidly.
Which of the choices below lists the successive stages in coal formation from first step to last?
accumulation of plant remains, peat formation, lignite formation, bituminous coal formation, anthracite coal formation
What are the six major igneous rock textures?
aphanitic, phaneritic, porphyritic, vesicular, glassy, and pyroclastic
In which two plate tectonic settings would one expect magma to be generated?
at a mid-oceanic ridge and at an oceanic-continental convergent boundary
Laccolith
bend the sedimentary layers above them, whereas the sedimentary layers below remain relatively undeformed.
Compare cinder cones to shield volcanoes.
cinder cones have steeper flanks than shield volcanoes, and cinder cones occupy a smaller area of land than shield volcanoes.
conduit
circular path through which magma ascends to the vent,
what causes rocks to melt in these settings?
decompression melting.
hydrothermal deposits
deposits of ore generated from hot, ion-rich fluids.
three basic categories of sedimentary rocks?
detrital rocks, which are composed of solid particles; chemical rocks, which are composed of ions that precipitated from solution; and organic rocks, which form from the carbon-rich remains of organisms
Granite and rhyolite are both ____, but they differ in ____.
felsic; crystal size
inorganic rock (sedimentary)
forms from non-biological processes, such as salt that is left behind when a lake evaporates
crater
funnel-shaped depression around the vent.
iron
gives rocks a reddish color
list the four basic compositional groups of igneous rocks, ranging from the highest silica content to the lowest silica content?
granitic, andesitic, basaltic, ultramafic
What are the three broad categories of sedimentary environments with an example of each?
marine environments, such as deep ocean floors; continental environments, such as deserts; transitional environments, such as tidal flats
What are the two basic categories of weathering?
mechanical and chemical
Where do most shield volcanoes form?
ocean floor
How are detrital rocks identified
primarily identified based on their particle sizes.
Which are the two most common minerals in detrital rocks?
quartz and feldspar
Which choice lists events in soil erosion from first to last?
raindrop impact, sheet erosion, rills, gullies, stream
What are the four types of oil traps, and what do they all have in common?
salt domes, fault traps, anticlines, and stratigraphic traps. All four require a porous, permeable reservoir rock that yields the natural gas and an impermeable cap rock that keeps the gas from escaping at the surface.
biochemical rock
sedimentary rock that was formed by organisms or contains the remains of organisms; like limestone
Diagenesis
the chemical, physical, and biological changes that take place after sediments have been deposited and during and after sediment lithification
what does the term "country rock" refer?
the crustal rocks into which igneous bodies intrude
What is produced when carbonic acid reacts with potassium feldspar?
the salt, potassium bicarbonate, and the mineral, kaolinite
vent
the surface opening of a conduit
Pahoehoe lava
thin and quick. ropy looking, smooth surface, very hot temps. Low viscosity
Scoria
vesicular ejecta that is the product of basaltic magma
graded bedding
when larger sediments are deposited at the bottom of the layer, gradually changing to fine sediments at the top.
cross bedding
when sediments are layered at an angle inclined to the horizontal
Calcite
which effervesces in dilute acid
silica
which produces the hardest sedimentary rocks
