Geology Test Chapters 4,5,6,7
Select the correct description of dikes and sills.
Dikes are discordant igneous intrusions and sills are concordant igneous intrusions; both are tabular.
Which of the following choices classifies the three listed rocks by composition and texture?
Diorite is intermediate with a phaneritic texture; rhyolite is felsic with an aphanitic texture; basalt porphyry is mafic with a porphyritic texture.
Contrast pahoehoe and aa lava flows.
Pahoehoe flows exhibit smooth surfaces, are hotter, and are more fluid than aa flows, which exhibit jagged surfaces with sharp edges.
In what way do tuff and volcanic breccia differ from other igneous rocks such as granite and basalt?
Tuff and volcanic breccia do not consistently belong to a single compositional category, unlike granite, which is always felsic, and basalt, which is always mafic.
What are the six major igneous rock textures?
aphanitic, phaneritic, porphyritic, vesicular, glassy, and pyroclastic
What is one way to limit soil erosion?
create grassy waterways
What are the 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
Which type of plate boundary generates the greatest quantity of magma?
divergent
Fill in the blanks in this sentence using the terms below: Granite and rhyolite are both ____, but they differ in ____.
felsic; crystal size
How are basaltic magmas thought to form?
from the partial melting of the ultramafic rock peridotite
What does a fumarole emit?
gases only
What is the source of magma for most intraplate volcanism?
mantle plumes
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
What does the term "texture" refer to when describing an igneous rock?
the appearance of a rock based on the size(s), shape(s), and arrangement of the mineral grains it contains
What is diagenesis?
the chemical, physical, and biological changes that take place after sediments have been deposited and during and after sediment lithification
What is produced when carbonic acid reacts with potassium feldspar?
the salt, potassium bicarbonate, and the mineral, kaolinite
What is a lahar?
a mudflow of volcanic debris saturated with water
Fill in the blanks using the choices below: 1.____ are two examples of building minerals, whereas 2.____ are two examples of industrial minerals.
1. gypsum and calcite; 2. sulfur and fluorite
What is the process that is thought to generate most granitic magmas?
A basaltic pond of magma becomes trapped below the continental crust and partially melts the silica-rich crust into a granitic magma.
How does climate influence the weathering of rock?
Areas with high temperatures and abundant moisture will generally have the highest rates of chemical weathering.
How do batholiths, stocks, and laccoliths differ?
Batholiths are the largest type of igneous bodies and occur in a linear fashion with a distance of 100km or more; stocks are smaller than batholiths; laccoliths bend the sedimentary layers above them, whereas the sedimentary layers below remain relatively undeformed.
Differentiate between the formation of biochemical rocks and the formation of inorganic chemical rocks.
Biochemical rocks form from organisms that were once alive, such as limestone from marine shells, whereas inorganic chemical rocks form from non-biological processes, such as salt that is left behind when a lake evaporates.
Why is soil considered an interface within the Earth system?
Changes in the climate in the atmosphere create changes in soil texture and composition. Water from the hydrosphere that is added to soil from various sources allows the soil to be able to sustain plant life, which returns to the geosphere once it expires.
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.
How are conglomerate and breccia different?
Conglomerate has rounded grains; breccia has angular grains.
How do light-colored igneous rocks differ from dark-colored rocks?
Dark-colored igneous rocks have a higher iron and magnesium content than light-colored rocks.
How does an exfoliation dome form?
Exfoliation, called "sheeting," is the process in which concentric slabs of rock break loose in reaction to the unloading of pressure and actions of manganese-fixing bacteria.
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.
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.
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.
What are some of coal's disadvantages? Select all that apply.
Mining coal still presents hazards to workers such as roof collapse, gas explosions, and working with heavy equipment. The surface mining of coal scars the countryside, causing land reclamation to be costly. Burning coal produces emissions that adversely affect the environment and human health.
Fill in the blanks using the choices below: ____ 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
Which statement accurately describes a pyroclastic flow?
Pyroclastic flows, which consist of hot gases infused with incandescent ash and lava fragments, can reach many miles away from their sources because they are nearly frictionless and are driven by gravity.
What type of structure is Shiprock, New Mexico, and how did it form?
Shiprock, New Mexico, is a volcanic neck that formed when the volcano itself eroded away, leaving the crystallized igneous rock piercing through the Mancos shale.
What role do water and other volatiles play in the formation of magma?
The addition of water and other volatiles allows the rock to melt at lower temperatures than if they had not been added.
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.
How might the direction that a slope is facing influence soil formation?
The direction the slope faces determines how much solar radiation that its soil will receive, which determines the soil's temperature and moisture content.
What is the geothermal gradient, and how does it relate to the melting curve of peridotite?
The geothermal gradient is the increase in temperature with depth under the Earth's surface. The melting curve of peridotite is consistently higher than the geothermal gradient.
In the above picture, why have the headstone on the right and the headstone on the left, both in the same cemetery, weathered differently?
The headstone on the left is made of granite, which is composed mostly of quartz and feldspar, whereas the headstone on the right is made of marble, which is composed of calcite.
How does the crystallization of igneous material occur?
The liquid igneous material cools, the ions within slow in their movement, and they pack more closely together. When sufficiently cooled, ions become confined to a crystalline arrangement.
What are the main gases released during a volcanic eruption?
The main gas released from a volcanic eruption is water vapor, along with carbon dioxide, nitrogen, and sulfur dioxide. These gases escape when pressure on the magma is reduced.
What is Bowen's reaction series?
The order in which specific minerals form as a magma cools.
How did Crater Lake form, and how does it compare to the calderas of shield volcanoes?
The summit of the composite volcano collapsed after an explosive eruption of silica-rich pumice and ash fragments; rainwater later filled this caldera. Had this volcano been a shield volcano, the collapse would have been a result of a gradual subterranean drainage of a central magma chamber.
What are the two primary factors that determine how magma erupts?
The viscosity and gas content of a magma determines how it erupts. Low viscosity and low gas content generally lead to quiescent eruptions.
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, and what causes rocks to melt in these settings?
Volcanism at divergent boundaries is most often associated with basaltic rock, which is created by decompression melting.
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.
In addition to composite volcanoes, what other type of volcanic landform can generate pyroclastic flow?
a lava dome
Which of the choices below correctly describes three types of common cements in sedimentary rocks?
calcite (which effervesces in dilute acid), silica (which produces the hardest sedimentary rocks), and iron (which gives rocks a reddish color)
For which sediment size is compaction most important as a lithification process?
clay
Of the five basic controls of soil formation, which factor is the most influential in soil formation?
climate
Complete the following sentence. When contrasting lava from composite volcanoes with lava from shield volcanoes,....
composite volcanoes most often produce silica-rich lavas with high viscosities, whereas shield volcanoes produce basaltic lavas with low viscosities.
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
