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Geology Midterm 2
Terms in this set (111)
Which of the following scenarios best describes how the Hawaiian Islands formed in the Pacific Ocean?
Magma generated from a hot spot burned through the overlying plate to create volcanoes
Which materials in Hawaii's lava help to keep it fluid for longer at the surface (as opposed to cooling and solidifying quickly), thus allowing extensive lava flows to develop?
magnesium and iron
Which of Hawaii's five volcanoes are still considered to be active?
Kilauea and Mauna Loa
Which of the following has the single most immediate effect on lava's ability to solidify?
What is piled up along the cone of SP Crater that causes it to be so steep?
What causes vesicles to form in lava?
trapped gas bubbles
What is the difference between aa lava and pahoehoe lava?
Aa lava has a prickly texture; pahoehoe has a smooth, ropy texture.
What is one way that cinder cones differ from composite and shield volcanoes?
Cinder cones are smaller than composite and shield volcanoes.
Which lava is thicker Basaltic or andesitic?
What features at Yellowstone National Park is evidence for a magma chamber beneath the park?
Geysers and hot springs (steam), Welded tuff, Rising (or bowing upward) ground near Yellowstone River
What pieces of evidence for a past volcanic eruption are present at Yellowstone National Park?
A caldera rim, Pyroclastic material, Lava flows
Yellowstone is best described as an active, dormant, or extinct volcano?
An active volcano that has erupted in the last 1 million years
What was a stage in the formation of Yellowstone caldera?
Crust bows upward above a magma chamber.
How are igneous rocks formed?
Igneous rocks are formed by the cooling and crystallization of molten rock.
Intrusive and extrusive igneous rocks are classified based on what criteria?
How quickly the molten rock cools and crystallizes, and where this occurs with respect to Earth's surface
What is required to generate an igneous rock with a fine-grained texture?
rapid cooling and crystallization
A phaneritic texture is characteristic of a(n) __________ igneous rock that cooled __________.
intrusive; below the surface
What does it mean if an igneous rock has an aphanitic texture?
The igneous rock exhibits mineral crystals too small to see with the naked eye.
Ultramafic rocks contain __________ and are commonly found in __________.
What is an accessory mineral?
A mineral that makes up a relatively small portion of the total rock composition
What is the difference between granite and rhyolite?
Granite is phaneritic and rhyolite is aphanitic.
an intermediate rock with two distinct grain sizes
What do pumice and scoria have in common?
They both exhibit a vesicular texture.
What factors describe the metamorphic conditions at a mid-ocean ridge?
low pressure; hot, watery fluids; low temperature
What factors describe the metamorphic conditions in a subduction zone?
high pressure and low temperature
What is an example of a metamorphic rock?
Which of the following is a temperature associated with metamorphism?
400 degrees Celsius
What role does hot ion-rich water play in the process of metamorphism?
Water migrates into host rock carrying ions to stable minerals in order to facilitate growth of new metamorphic minerals.
By what process did the gabbro turn into amphibolite?
The gabbro was heated to 500 °C and buried a few miles below the Earth's surface.
What is a mantle plume?
hot mantle rock rising from deep within the Earth
What kind of metamorphic texture results in the segregation of light and dark mineral bands?
Why are garnets used in sandpaper?
Garnets have a value of 8 or 9 on the Mohs Hardness Scale, making them very abrasive.
Define depositional environment?
an area where sediment was deposited under certain conditions in Earth's past
What is a delta?
A delta is a triangular landform created where a stream enters a body of water and deposits sediment.
Other than sand dunes in a desert environment, where else would you expect to find well-rounded and sorted sand deposits?
Describe the distribution of sedimentary deposits you would expect to find on a delta.
sand in channels, mud on floodplain
If all the particles in a detrital sedimentary rock are nearly the same size, it is __________.
very well sorted
A smooth grain shaped like a cigar is __________ and shows __________.
well-rounded; low sphericity
Wind-blown sand deposits would most likely be __________ and __________.
very well-sorted; well-rounded
Which of the following correlate to transport distance?
grain size and rounding
A conglomerate is poorly sorted with well-rounded grains. This rock was likely formed in what depositional environment?
formed by the solidification of melts
formed by cementing of grains from pre-
existing rocks, or precipitation of minerals from water solution
formed when preexisting rock is changed by heat or pressure
Igneous rock classification is based on
composition and texture
Texture reveals the
• Fast cooling—smaller crystals.
• Slow cooling—larger crystals.
-Continental composition and light color.
-Mixed continental-oceanic composition.
-Ocean floor composition and dark color.
less than 50% silica.
Bowen's Reaction Series
Shows that mafic minerals form at higher temperatures than felsic minerals
formed by freezing of magma below ground.
formed by freezing of lava above ground.
vertical, wall-like intrusion
horizontal, tabular intrusion
have records of historic eruptions.
show evidence of activity in past hundred to thousand years, but no historical eruptions are known.
eroded, has not erupted in thousands—if not millions—of years.
Most volcanic hazards are associated with
convergent plate tectonic boundaries.
(Think Pacific Ring of Fire)
internal resistance to flow. Magma viscosity corresponds with silica content, as silica tends to polymerize.
Felsic and intermediate magmas
higher silica, high viscosity, tend to explode.
lower silica, low viscosity, tend to flow.
measure changes in ground surface as a result of moving magma
measure earthquakes associated with magma movements.
can indicate changes in magma composition.
are small, bulbous masses made of high silica lava that does not flow easily.
large circular depression that forms following large explosive eruption and/or collapse of magma chamber
broad, flat plains of volcanic rock.
(Low silica magmas may also erupt from fissures in continental settings.)
are small volcanic hills composed of tephra—fragments of volcanic material ranging in size from ash to boulders.
(Cinder cones usually one-time events)
loose fragments of rocks or minerals, mineral crystals that precipitate from water solution, and shells formed from organisms.
forms at or near surface from cementation of loose grains, precipitation of minerals from solution, or cementation of shell fragments.
processes that break up and/or corrode solid rock, eventually transforming it into sediment.
What are two categories of weathering
physical and chemical
Physical (mechanical) weathering
breakup of rocks into unconnected grains or chunks without changing the rock's chemistry.
natural cracks formed in rocks due to cooling or removal of overburden
formation of onion-like sheets parallel to rock surface. Common in granites.
accumulation of loose bedrock blocks forming an apron of rubble at the base of a slope
expansion of a joint by external agent
expansion of joint by ice
expansion of joint by root.
expansion of joint by precipitated salt crystals.
changes in a rock's mineral composition leading to breakdown of the rock.
minerals dissolved by water
Fastest Weathering has what kind of stability?
Slowest Weathering has what kind of stability?
Physical weathering aids chemical weathering by
creating surface area.
Chemical weathering aids physical weathering by
weakening the attachments between grains.
Clastic (detrital) sedimentary rock type is
cemented-together fragments and grains derived from pre-existing rocks.
Chemical sedimentary rock type is
composed of minerals that precipitate from water solutions. Usually carbonates, e.g., limestone.
compaction and cementation
-transforms loose sediment into rock.
Weathering that forms clastic rocks creates
removes sediment from source
moves sediment by wind, water, or ice to a new location
allows sediment to settle from its transporting medium
rocks made from carbonate minerals, e.g., calcite.
Carbonate minerals precipitate in
clear warm shallow water:
- Common in low latitudes.
- Common in shallow water.
- Not much clastic sediment.
Chert, a Chemical Sedimentary Rock, is composed of
Evaporites, a Chemical Sedimentary Rock, is formed by
evaporation of saltwater.
formed by replacing calcite in limestone with dolomite CaMg(CO3)2
calcite precipitated in layers
Sedimentary rock with 50% or more organic material.
is a proton donor
Foliation is in what direction to the differential stress
What is the protolith of Quartz
What is the protolith of Marble
Carbonate like limestone or calcite
What is the protolith of Hornsfell
various rock types with high temp and low differential type
Metamorphic rock can be found
local to the heat source
What are examples of volcanic glass?
obsidian and pumice
Name the kind of volcanoes from largest to smallest
Shield, Strata, Cinder
What is a lahar
ash + water, mud flow
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