Geology Exam 3

Front 1

What igneous rock is the most mafic?

Back 1

Gabbro

Front 2

What mineral is the most abundant in igneous rocks of intermediate composition?

Back 2

Plagioclase feldspar

Front 3

What igneous rock has the same chemical composition as a diorite?

Back 3

Andesite

Front 4

What pair of intrusive and extrusive igneous rocks do not both have the same chemical composition?

Back 4

Peridotite and basalt

Front 5

What is the effect of water on rock melting?

Back 5

Water lowers the melting temperature of a rock

Front 6

Which is less dense, molten or solid rock?

Back 6

Molten rock is less dense than solid rock

Front 7

During crystallization of a magma, plagioclase feldspar becomes richer in:

Back 7

Sodium

Front 8

The process of magmatic differentiation explains how:

Back 8

Rocks of varying composition can arise from the same parent magma

Front 9

What type(s) of rock(s) crystallize at the highest temperature?

Back 9

Basalt

Front 10

What are the most common igneous rocks found in ophiolites?

Back 10

Basalts and gabbros

Front 11

What melting processes is important beneath mid-ocean ridges?

Back 11

Decompression melting

Front 12

In what tectonic setting would you expect to find intermediate igneous rocks?

Back 12

Subduction zones

Front 13

What are not involved in classifying igneous rocks?

Back 13

-texture

-group of minerals making up rock

-chemical composition of the rock

Front 14

Igneous rocks with crystals too small to be seen without a microscope are:

Back 14

Aphanitic

Front 15

Intermediate igneous volcanic rock is:

Back 15

Andesite

Front 16

Felsic, intermediate, and mafic igneous rock all are dominantly made up of ___________ minerals.

Back 16

Silicate

Front 17

Almost the entire ocean floor is comprised of which igneous rock?

Back 17

Basalt

Front 18

The dominant rock of Earth’s mantle is:

Back 18

Peridotite

Front 19

The most plentiful minerals in peridotite are:

Back 19

Pyroxene and olivine

Front 20

What causes a decrease in melting temperature of rocks?

Back 20

-decreasing pressure

-increasing water content

-more Felsic composition

Front 21

Bowen’s Reaction Series summarizes:

Back 21

The different temperatures at which different silicate minerals form

Front 22

The presence of _________________ in subduction zones lowers the melting temperature and viscosity of resulting magmas over subduction zones.

Back 22

Water

Front 23

While basalt is erupting to the ocean floor at mid-ocean ridges, ___________ is crystallizing in underlying magma chambers.

Back 23

Gabbro

Front 24

Igneous rocks of Iceland:

Back 24

Mid-ocean ridge basalts

Front 25

What about the viscosity of lavas is true?

Back 25

Lava viscosity increases as the lava increases as it becomes more sialic

Front 26

What is the eruption temperature of rhyolitic lava?

Back 26

600-800 *C

Front 27

What volcanic features is NOT generally associated with basalt?

Back 27

Volcanic domes

Front 28

Which of the following sequences of volcanic rocks are in the correct order of increasing sialic content?

Back 28

Basalt, andesite, rhyolite

Front 29

What volcano is NOT a composite volcano (stratovolcano)?

Back 29

Mauna Loa, Hawaii

Front 30

What is the term for a large, steep-walled, basin-shaped depression that forms by the collapse of a magma chamber roof after a violent eruption?

Back 30

Caldera

Front 31

What lava type erupts in sheets from fissures to build a lava plateau?

Back 31

Basalt

Front 32

Volcanic domes are associated with ________ magma.

Back 32

Sialic

Front 33

What gases are NOT an important constituent of volcanic gas?

Back 33

-carbon dioxide

-sulfur dioxide

-water vapor

-hydrogen sulfide

Front 34

Which mountain chains are made up primarily of volcanoes formed at an ocean-continent subduction zone?

Back 34

Andes

Front 35

Large igneous provinces like the Columbia River Plateau are formed from the successive eruptions of:

Back 35

Flood basalt

Front 36

Which volcanic eruptions resulted in the deaths of over 20,000 people?

Back 36

Nevado del Ruiz, Colombia, 1985

Front 37

Mantle plumes are thought to originate at the ___ boundary.

Back 37

Core-mantle

Front 38

The ___________ is the main source of magma for the production of igneous rocks.

Back 38

Asthenosphere

Front 39

The liquid magma that reaches Earth’s surface is called:

Back 39

Lava

Front 40

What component of magma is required to cause violent volcanic eruptions?

Back 40

Dissolved gases

Front 41

Lava viscosity increases as:

Back 41

Silica content increases and lava temperature decreases

Front 42

The three major rock products of erupted lavas are:

Back 42

Basalt, rhyolite, and andesite

Front 43

Basaltic lavas form shield volcanoes and flood basalts rather than steep stratovolcanoes because:

Back 43

Low silica results in low-viscosity, fluid lava

Front 44

Basaltic pillow lavas are a strong indicator of:

Back 44

Basaltic lava that erupted into water

Front 45

Why are lava domes associated with felsic lavas?

Back 45

The high SiO2 lavas bulge upward but don't flow

Front 46

The Mount Pelée eruption of 1902, a mixture of hot air and ash, was a:

Back 46

Pyroclastic flow

Front 47

What is the largest volcano on Earth?

Back 47

Mauna Loa, Hawaii

Front 48

What is the proper term for the huge volcanoes with very gentle slopes?

Back 48

Shield volcanoes

Front 49

The probable source of Earth's oceans and atmosphere is:

Back 49

Water and atmosphere escaped from Earth's interior in volcanic eruptions

Front 50

In 1816, known as “the year without a summer,” summer frosts and snowstorms occurred in the Northern Hemisphere as a result of:

Back 50

Sunlight blocked by debris in atmostphere from eruption of Tambora

Front 51

Magmas in subduction zones are produced primarily by:

Back 51

Fluid-induced melting

Front 52

Subduction zone volcanoes produce rock of dominantly _____ composition

Back 52

Andesitic

Front 53

Weathering process is subdivided into:

Back 53

Physical and chemical

Front 54

As sediment is transported downstream, the particles tend to become:

Back 54

Rounded and smaller

Front 55

Which sedimentary rocks has the largest particle sizes?

Back 55

Conglomerate

Front 56

Sediment is deposited as:

Back 56

Currents slow down

Front 57

The process that mobilizes the particles produced by weathering:

Back 57

Erosion

Front 58

The process that breaks rocks into smaller pieces that are not changed in composition:

Back 58

Physical weathering

Front 59

Sedimentary rocks are a primary source of information about:

Back 59

-past climates

-evolution of life on Earth

-energy resources

Front 60

Consider three undeformed horizontal beds of sedimentary rocks. What layer is the oldest?

Back 60

Lower

Front 61

A nonconformity is:

Back 61

A gap in the geologic record bounded below by metamorphic or igneous rocks and bounded above by sedimentary rocks