Geology ch4-8

The original volcano Mount Mazama erupted to form Crater Lake, Oregon
A___is a volcanic depression much larger than the original crater, formed when the volcano collapses into a vacated magma chamber.
__describes the surface of a basalt flow with a smooth ropy surface.
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Major volcanic peaks of the Cascade Mountains, like Mt. Rainier, Mt. Shasta, Mt Hood, and Mt St Helens, have been active volcanos for 30 to 40 million years.
Shield volcanos have _bases and_ inclined slopes.
broad, gently
What are the three factors that influence viscosity of a lava?
temperature, composition, dissolves gasses
Most of the gas released by volcanic eruption is sulfur dioxide.
Occasionally, a volcano will spew large amounts of fine volcanic dust into the high atmosphere. This dust can have the effect of_.
All of the answers are correct
_describes the surface of a basalt flow with a jagged, rubble surface.
Silica lavas, which are relatively high in silica, tend to be more fluid than mafic magmas
Weather volcanic ash and lava produce excellent fertile soils.
The last volcano to erupt in the continental 48 states was_
Mt. St. Helens
Tuff is a rock composed of fine-grained pyroclastic particles.
The large pyroclasts are_
_are tunnel like caves within a lava flow.
Lava tubes
Pillow structures, pillow-shaped rounded masses, form where lava is extruded under water.
How do scientist indicate the power of volcanic eruption?
volcanic explosive index
The most common mafic volcanic rock is
The more_ the lava, and the greater the amount of gas trying to escape, the more violent the eruption.
Volcanic eruptions have no effect on climate.
Composite volcanoes are also called cinder cones volcanoes.
The Roman city of_ was destroyed by the eruption of Vesuvius in 79 AD.
The island of the Hawaiian chain are an excellent example of a series of_
shield volcanoes
The most abundant silicic volcanic rock is_
A_ volcano is composed of alternating layers of pyroclastic fragments and solidified lava flows.
The island o Hawaii are essentially a series of shield volcanoes built upward from the ocean floor over million years.
The eruption of_ is related tot he fact that the North American plate is overriding a portion of the Pacific Ocean floor.
Mount St. Helen
The term_ is used for molten rock on the Earth surface
Pahoehoe lava is characterized by a ropy or billowy surface.
Earth is the only major body in the solar system on which there are active volcanoes.
The single most important agent for the chemical weathering is temperature.
Chemical weathering generally proceeds_
along contacts between mineral grains
Water that has trickled down into a joint in a rock can freeze, expand, and_
widen the crack and hastening the rock’s disintegration
The_ horizon is the incompletely weathered parent material lying below the B-horizon
the process of chemical weathering is also called
rock decomposition
Plants and burrowing organisms contribute to soil development by
all answers are correct
At the surface of the earth, ultramafic rocks in kimberlite pipes weather away leaving behind concentration of_
_is wind transported and deposited sediment
Sulfuric acid is produced naturally during_
some volcanic eruptions
Ordinary rain has a pH of about 5.5 to 6 from the carbon dioxide in the atmosphere and from natural sources of acid sulfur gases
Plants such as roots growing in cracks, and animals compacting the soil have little influence on mechanical weathering.
Ferromagnesian minerals such as pyroxene, amphibole, biotite, and ovaline are chemically altered in the presence of_
Oxygen is abundant in the atmosphere but it does not combine with minerals of the Earth’s crust.
_is weathered unconsolidated material on top of solid bedrock
_are commonly left after complete chemical weathering
Quarts and clay material
All rocks chemically weather the same way
The B-horizon in soil is the zone of accumulation
The_ horizon is the dark colored soil horizon that is rich in organic materials and forms just below the surface vegetation
As soils mature, distinct layers called _appear
Frost wedging is most effective_
in areas with many days of freezing and thawing
_is a byproduct of rock weathering
The most important natural source for the formation of acid rock weathering at the Earth’s surface is dissolved_
carbon dioxide
The term mechanical weathering refers to changes in a rock that are physical: there is little or no chemical change
Hydrogen Ions give off by natural acids can disrupt the crystal structure o most minerals, making the structure susceptible to further decomposition
A_ soil is one that develops from the bedrock directly beneath it
_is the mineral least susceptible to chemical attack on the Earth’s surface
_is picking up and physical removal of rock particles by an agent such as wind, flowing liquid water, or glaciers
The_ horizon is the upper most layer of a soil; it consist of organic material
_refers to a group of destructive process that change the physical and chemical character of rocks at the Earth’s surface
In tropical regions where temperatures are high and rainfall abundant, highly leached soils called_ (oxisols) form
laterite soil
Sand grains can be distinguished from silt grains by_
the gritty feelings between the fingers
Boulders include all rounded particles coarser than 2 mm in diameter
_are massive deposits of limestone
_is a general term for the processes that convert loose sediment into sedimentary rock
_is the process by which sediment grains are selected and separated according to grain size by agent transportation
_is a hard compact, very fine grained sedimentary rock composed entirely of silica
_is an organic rock formed from the compression and alteration of plant remains such as leaves, twigs and tree trunks
_limestones have clastic texture
Under what conditions is a sediment considered to be well-sorted
when the grains are nearly all the same
Under what conditions is a sediment considered to be well-sorted?
when the grains are nearly all the same size
A sandstone with more than 25% sand-sized feldspar is an arkose
_are polygonal patterns that form in very fine sediment as it dries.
Mud cracks
Sedimentary rocks can form from the deposition of solid particles eroded from pre-existing rock or from the deposition of the hard parts of organisms
Silt is mostly composed of_ grains
_are sedimentary rocks deposited by direct precipitation of minerals from water
chemical rocks
_forms only in fine grained sediments that are exposed to air
Peat is a brown lightweight unconsolidated deposit that ultimately can transform into
Lithification is the general term for the processes that covert loose sediment into a sedimentary rock
_is the shift to a tighter packing of sediment grains due to the weight of overburden
A sedimentary rock that consist of sediment grains bound by cement into a rigid framework is called_
The most common cements are_and_
silica, calcite
A_ is a body of sediment deposited when a river flows into standing water, like a lake or sea
_is a sedimentary rock formed by the cementation of coarse angular fragments of rubble
Asymmetrical_ are produced by current flowing in a single direction
ripple marks
In order of decreasing size(largest listed first), sedimentary grain sizes include_
gravel, sand, silt, clay
A_ is a sandstone containing a significant amount of feldspar
Oil and natural gas originate from_ in marine sediments
organic matter
_sediments are deposited or precipitated as a result of the action of organisms
_is a coarse grained sedimentary rock formed by the cementation of rounded gravel
A_ is a layer of sedimentary rock with a vertical charge in particle size, usually from coarse at the bottom to fine at the top.
graded bed
Hot water (or vapor) is the most important fluid involved in metamorphic processes
Meteor craters show an unusual type of metamorphism called shock metamorphism
In some instances a single mineral, a_, suffices for determination of the pressure and temperature under which a metamorphic rock formed
metamorphic index mineral
_stress is a type of deferential stress
_ forms when a limestone recrystallizes during metamorphism
Because of the ease with which it can be split into thin flat sheets, this metamorphic rock is used for making chalkboard, pool tables and roofs.
Metamorphic rocks forms pre-existing rock when heat and pressure cause solid-state transformation
If limestone is metamorphosed at relatively low temperatures and pressure it recrystallizes into marble
_are important economic resources for lead, zink, gold, silver, tungsten, tin and mercury
Hydrothermal veins
The major classification of metamorphic rocks divides them into foliated and non-foliated groups
_metamorphism takes place at considerable depth underground(generally greater than 5km)
_tends to deform objects into oblong or flattened forms
differential stress
The zone of contact metamorphism(the aureole), _
is commonly rather narrow, from 1-100 meters wide
Confining pressure is pressure applied equally on all surfaces of a substance as a result of burial or submergence
Metamorphism may involve all of the following except_
complete melting of the rock
Andalusite, kyanite, and sillimanite are among the best known index minerals that provide information about the temperature and pressure of metamorphism.
_ is the pressure felt by deeply buried rock
Schist is a metamorphic rock characterized by a ninfoliated texture
A metamorphic rock is similar both in mineralogy and texture to its parent rock
Contact metamorphism occurs adjacent to a pluton when a body of magma intrudes relatively cool country rock
_ is a fine grained metamorphic rock whose parent rock was basalt
The two most common non-foliated metamorphic rocks are_ and marble
_ metamorphism is a term used for the process in which rocks are altered by hot water
Any new mineral that has crystalized under high pressure conditions tends to occupy less space than did the mineral or minerals from which it formed
_ is a metamorphic rock with distinct light and dark layers that formed at high temperatures and pressures
The deeper a rock is below the earth’s surface_
the hotter it will be
_ is the lowest grade rock in progressive metamorphism
_ metamorphism occurs adjacent to a pluton when a body of magma intrudes a relatively cool country rock
_ is pressure applied equally to all surfaces of a substance as a result of burial or submergence
Confining pressure
Lines connecting points of equal temperature on maps or cross sections are called_
The earth is approximately _ years old
The relative dating principal of _ states that fragments include in a host of rock are older than the host rock
The principle of _ states that fragments include in a host rock must be_ than the host rock
Inclusion, older than
By the principal of_ the surface feature known as the Grand canyon is- than the sedimentary formations that are exposed in the side walls of the Grand Canyon
cross cutting relationships; younger
Fossils are common in
sedimentary rocks
Relative time refers to the time sequence in which events take place rather than the number of years involved
Under some circumstances, correlation between two regions can be made by assuming that similar rock types in the two regions formed at the same time
Alvarez and other proposed a hypothesis that dinosaurs occurred because
one or more steroids impacted the earth, resulting in environmental changes
In radioactive decay a_ emission is the emission of two neutrons and two protons from a nucleus
An index fossil is a fossil from a very short-lived geographically widespread species known to exist during a specific interval of geological time
The_ Era is the Age of Mammals
The principal of superposition states that within a sequence of undisturbed sedimentary rocks, the layer get younger going from bottom to top
Isotope dating has shown that the Precambrian took up_ % of all geological time
_ donates the vast amount of time that precedes the Paleozoic Era
Our ability to assign an age to geological an archeological materials is based on our ability to measure the relative abundance of radioactive_ and their stable decay products
Geologist use fossils in sedimentary rocks to assign their correct place in geological history.
_ is the spontaneous nuclear change o isotopes with unstable nuclei
Radioactive decay
Half life is the time for a given amount of a radioactive isotope to decay to half it’s original amount
the Mesozoic Era precedes (is older than) the Paleozoic Era
Earth is between 1 and 2 billion years old
Isotopes date from volcanic ash or lava flows layers between fossiliferous sedimentary rocks have been used to assign numerical ages to the geologic time scale
In geology,_ usually means determining time equivalency of rock units
The principal of_ states that an original sedimentary layer extends laterally until it tapers or thins at is edges
lateral continuity
The_ of a radioactive material is the time it takes for a given amount of radioactive isotopes to be reduced by half.
half life
The half life of the carbon 14 isotope is 5730 years. If there were 4 billion atoms of C-14 in a particular organism at the time it died, how many atoms of C-14 would there be in the remains of that organism 11,460 years after it died?
1 billion
In the radioactive decay process of_ decay an electron is emitted from the nucleus of the parent isotope.
The principal of original horizontal states that beds of sediment are nearly always deposited as nearly horizontal layers
In the radioactive decay process of electron capture a_ in the nucleus captures an orbiting electron.
When the_ came to a close, dinosaurs became extinct
When marine geologist collects a core of unreformed ocean-floor sediment, they know that the youngest layer if on the top of the core and the oldest is at the bottom because of the principal of_

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