Geology Chapters 4 & 5

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

Which of the following pieces of evidence for a past volcanic eruption are present at Yellowstone National Park? -Lava flows -Human documentation -Pyroclastic material -A cone shaped volcano -A caldera rim

-Lava flows -Pyroclastic material -A caldera rim

Which of the following could cause rock to melt? -change in composition -decrease in temperature -increase in pressure -decrease in pressure -increase in temperature

-change in composition -decrease in pressure -increase in temperature

What three factors do volcanologists monitor in order to determine whether magma is migrating toward the Earth's surface?

-changes in the patterns of earthquakes caused by the movement of magma -inflation of the volcano -the gases released from the volcano

Which of the following objects has a size similar to that of lapilli?

A marble (15 mm)

How does the viscosity of the magma fed to volcanoes affect nearby life and property?

A volcano that expels highly viscous magma is a greater threat to life and property because it is more explosive and thus is more difficult or impossible to predict.

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.

Yellowstone is best described as which of the following?

An active volcano that has erupted in the last 1 million years

When Eyjafjallajökull erupted in March 2010, ash plumes drifted southeast over Europe and, as a result, the controlled airspaces over many European countries were closed to air traffic, stranding thousands of people worldwide. Why would flying a commercial jet through a cloud of volcanic ash be dangerous?

Ash impairs visibility, clogs engines, and abrades engine parts.

What kind(s) of lava generate a cinder cone?

Basalt

Which of the following is the volcanic feature in which magma rises through before it is released at the surface?

Conduit leaves at a vent, may have a shape of a crater (pit or hollow)

Which of the following was a stage in the formation of Yellowstone caldera?

Crust bows upward above a magma chamber.

Which type of plate boundary generates the greatest quantity of magma?

Divergent

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.

You have found a mafic rock with a phaneritic texture. What is a potential rock name?

Gabbro

Which of the following is true based off your observation of intrusive igneous rocks on Earth's surface?

Intrusive igneous bodies are formed by magma intruding and crystallizing in country rock below Earth's surface. Therefore, if we observe these features at the surface today, they must be exposed by uplift and erosion.

What kind of viscosity would flood basalts have?

Low viscosity

Which of the following is true about mafic igneous rocks?

Mafic igneous rocks are rich in Fe, Mg, and Ca.

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.

Tabular Intrusions in Sedimentary Country Rock

Magma must first be emplaced below Earth's surface into country rock, and then crystallizes to form a dike. Less resistant sedimentary rocks were worn away by erosion, creating this extensive "wall-like" feature. Finally, humans constructed a tunnel through the wall instead of building a road around it.

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

Dark rocks= Light rocks=

Magnesium rich- iron, magnesium and calcium, higher melting temp Silica rich- potassium and sodium, lower melting temp Light to Dark Compositions Felsic Intermediate Mafic Ultramafic

Which of Hawaii's five volcanoes are still considered to be active?

Mauna Loa and Kilauea

Volcanic ash is best described as which of the following?

Microscopic pieces of rock ejected by a volcano

Based on the diagram shown in the video, name two minerals that are unlikely to coexist in the same igneous rock.

Muscovite and Pyroxene

What is the most likely rock texture of the dike and stock?

Phaneritic

What gets shot out of a volcano?

Pyroclastic materia lash lapilli blocks- leave as solids and land as solids bombs- leave as liquids and land as solids

Based on what you learned in this video, what minerals make up rhyolite?

Quartz, K-feldspar, and plagioclase feldspars, with relatively fewer biotite and amphiboles

Which of the following features at Yellowstone National Park is evidence for a magma chamber beneath the park? Rising (or bowing upward) ground near Yellowstone River Welded tuff Geysers and hot springs (steam) Actively flowing lava A thin, recent layer of volcanic ash

Rising (or bowing upward) ground near Yellowstone River Welded tuff Geysers and hot springs (steam)

What is scoria, and how does it differ from pumice?

Scoria-a vesicular ejecta that is produced from mafic magma pumice-also vesicular, it differs from scoria in that pumice is felsic.

Which group of minerals makes up most igneous rocks?

Silicates

Why is decompression melting common at mid-ocean ridges but not at subduction zones?

Tectonic plates are moving apart at mid-ocean ridges, resulting in a lowering of pressure beneath the ridge. Tectonic plates are moving together at subduction zones, resulting in an increase of pressure under new mountains.

Why is water a necessary component of the melting process in subduction zones?

The addition of water lowers the melting temperature of rock.

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 is the best interpretation for how the porphyritic texture of these rocks formed?

The magma cooled slowly at first, forming large crystals, and then quickly, forming small crystals from the remaining magma. A porphyritic texture is characterized by two distinct grain sizes, which suggest both slow and fast cooling rates. The larger feldspar and hornblende crystals result from a period of relatively slow cooling, while the surrounding gray fine-grained crystals resulted from a later period of rapid cooling. One hypothesis is that the large crystals were formed by slow cooling in a magma chamber, while the small crystals were formed during intrusion at a more shallow depth in the crust.

What substance makes ion migration easier in the later stages of magma crystallization, which allows abnormally large mineral crystals to form and create pegmatites?

Water

Where does the water involved in melting at subduction zones come from?

Water contained within minerals in the subducting plate is released during metamorphism.

How does the composition of a typical lava dome differ from that of a typical fissure eruption?

a lava dome's flow- silica-rich and has a high viscosity fissure eruption-basaltic and has a low viscosity.

Which of the following would decrease the viscosity of magma?

an increase in tempature

When contrasting lava from composite volcanoes to lava from shield volcanoes,

composite volcanoes-most often produce silica-rich lavas with high viscosities shield volcanoes-produce basaltic lavas with low viscosities.

Which two processes commonly generate magma?

decompression melting and wet melting (the addition of volatiles)

Tsunami

destructive sea wave triggered by powerful explosions or landslides into large bodies of water.

Lahar

fluid mudflow of volcanic debris.

Igneous rocks of felsic composition have __________ and __________ relative to mafic igneous rocks.

greater silica; lower melting temperature

The volcanoes in the Ring of Fire are generally described as

having violent eruptions, as most of these volcanoes are composite cones which eject andesitic lava.

Pyroclastic flow

hot, fast-moving body of expanding gas and ash that hugs the flanks of the volcano.

Ash falls

large volumes of ash precipitating from eruption cloud.

Which of the following volcanic materials flows out of a volcanic vent?

lava

Sideways conduit vent

parasitic cone, lava leaves this

The partial melting of ____ will yield mafic (basaltic) magma.

peridotite

Volcanic gases

substances like CO2, SO2, Cl, and F that can result in climate change and be hazardous to human health.

Which of the following has the single most immediate effect on lava's ability to solidify?

temperature

The texture of an igneous rock describes

the appearance of a rock based on the size(s), shape(s), and arrangement on the mineral grains it contains.

What are the three components of magma?

the liquid portion (mobile ions of the eight most common minerals found in the Earth's crust) called melt, the solid portion which consists of silicate mineral crystals, and the gaseous portion called volatiles

What factors influences the texture of an igneous rock?

the rate at which the rock cools, the amount of silica that is present in the magma from which it forms, and the amount of dissolved gases present in said magma

What is peridotite?

the rock making up the mantle

The volcanic islands in the above figure were created as the tectonic plate passed over a hot spot in the mantle. Based on the ages of the volcanic islands, in what direction was the tectonic plate moving toward? 15-12-8-4

toward the west <----