Geology Quiz 3 - Ch. 4

Examine Bowen's Reaction Series diagram. Which mineral has the highest temperature of crystallization? 1. olivine 2. quartz 3. pyroxene 4. Mica 5. k-spar

olivine

Unmelted pieces of country rock incorporated within the igneous rock mass are called _______. 1. assimilation 2. partial melting 3. assimilation material 4. xenoliths

xenoliths

Which of these relatively recent volcanic eruptions formed a caldera? 1. Mt. Fuji 2. Paracutín 3. Mt. St. Helens 4. Mauna Loa 5. Yellowstone

yellowstone

Deep-sea hydrothermal vents (black smokers) are most commonly located at what plate boundary? 1. convergent boundaries with oceanic to oceanic plate subduction 2. divergent boundaries of the mid-ocean ridge 3. convergent boundaries with subduction zones 4. divergent boundaries of the East African Rift

Divergent boundaries of the mid-ocean ridge

Which rock composition has the most amount of iron and magnesium? 1. felsic 2. intermediate 3. ultramafic 4. mafic

ultramafic

Bowen's Reaction Series has been expressed as a Y-shaped diagram containing how many minerals? 1. 6 2. 9 3. 8 4. 4 5. 5

8

Why does partial melting occur? 1. Because some minerals are harder than others 2. Because some minerals have lower melting points than others 3. Because some minerals have 3D structures 4. Because the mantle is solid, only some minerals can melt 5. Because some minerals have iron and magnesium

Because some minerals have lower melting points than others

How does the silica content affect the behavior of magma? 1. Higher silica makes the magma have more carbon. 2. Higher silica makes the magma more viscous 3. Higher silica makes the magma flow easier 4. Higher silica makes the magma cool faster. 5. Higher silica makes the magma have less volatiles.

Higher silica makes the magma more viscous

A rock with aphanitic texture and dark color is best identified as a _______________. 1. pegmatite 2. diorite 3. basalt 4. gabbro 5. granite

basalt

What does a P-T diagram of the mantle show? 1. It shows how the mantle is liquid magma under the surface. 2. It shows how Celsius and kilobars change. 3. It shows that rocks in the subsurface can never melt. 4. It shows how temperature increases but pressure decreases with depth. 5. It shows how pressure and temperature increase with depth.

It shows how pressure and temperature increase with depth

A porphyritic igneous rock has what defining characteristic? 1. Lots of quartz 2. Aphanitic crystals 3. Very low silica content 4. Phaneritic crystals 5. Larger crystals in a finer grained groundmass

Larger crystals in a finer grained groundmass

Most volcanoes on the sea floor erupt ________. 1. As cinder cones 2. Quietly with basaltic magma 3. Explosively with basaltic magma 4. Explosively with felsic magma 5. Quietly with felsic magma

Quietly with basaltic magma

What is the process by which decompression melting produces magma at divergent plate boundaries? 1. reduction of pressure at constant temperature 2. addition of heat at constant depth 3. addition of fluid at constant pressure 4. Increase of temperature at constant pressure

Reduction of pressure at constant temperature

If volatiles such as water vapor and carbon dioxide are added to a rock, what will happen to the melting temperature? 1. The melting temperature will not change. It is dependent on the pressure. 2. The melting temperature of a rock will increase. 3. • The rock will expand increasing the pressure. 4. The melting temperature of a rock will decrease.

The melting temperature of a rock will decrease

What does the Bowen Reaction Series show about the mineral composition of igneous rocks? 1. Aphanitic rocks are always mafic in composition. 2. Pyroxene and orthoclase are commonly found together. 3. Peridotite in the mantle is usually molten. 4. Calcium rich plagioclase is the first mineral to melt as a rock is heated. 5. The minerals in igneous rocks form in separate groups that depend on the temperature at which they crystallize.

The minerals in igneous rocks form in separate groups that depend on the temperature at which they crystallize

As magma travels up from the asthenosphere through the lithosphere into continental crust, how will fractional crystallization change the chemistry of an ultramafic magma? 1. The ultramafic magma will become more iron-rich. 2. The ultramafic magma will become more mafic. 3. The ultramafic magma will become depleted in potassium. 4. • The ultramafic magma will lose sodium.

The ultramafic magma will become more mafic

A pegmatite is characterized by __________ that forms from __________. 1. Low silica; intrusions of ultramafic magmas 2. Medieval window panes; demands of the very wealthy 3. Pockets of fluid; volatiles extruded from cooling magma 4. Lots of quartz; rapid cooling of felsic magma 5. Very large crystals of felsic composition; very slow cooling of residual material expelled from cooling magma

Very large crystals of felsic composition; very slow cooling of residual material expelled from cooling magma

The crystallization process in which a rising magma diapir incorporates some of the surrounding country rock so that the chemistry of the magma changes is called _____. 1. xenolith 2. assimilation 3. lower density magma rising through higher density country rock 4. fractional crystallization

assimilation

Explosive silica-rich volcanoes will be located mostly at ______. 1. convergent plate boundaries with continental to continental plate collisions 2. divergent boundaries of the East African Rift 3. convergent plate boundaries with subduction zones 4. divergent boundaries of the mid-ocean ridge

convergent plate boundaries with subduction zones

Where do igneous rocks with a coarse-grained (phaneritic) texture form? 1. deep under the surface. 2. on top of the surface. 3. on top of the surface after being ejected into the air. 4. Submarine lava flows 5. close to the surface but also just below it.

deep under the surface

A basaltic intrusion that cuts across layers of sedimentary rocks is called a _______. 1. batholith 2. dike 3. sill 4. laccolith 5. stock

dike

What causes igneous rocks to develop a fine-grained (aphanitic) texture? 1. Slow cooling 2. Very high pressures 3. Fast cooling 4. Lots of volatiles 5. Very high temperatures

fast cooling

Crystal settling would be another name for ______. 1. xenolith formation 2. fractional crystallization 3. assimilation 4. Bowen's Reaction Series

fractional crystallization

Which of these is NOT a means by which magmas are generated in the Earth? 1. Flux melting 2. Liquid melting 3. Added heat melting 4. Decompression melting

liquid melting

Partially melting an ultramafic rock produces a magma with a(n) _________ composition. 1. intermediate 2. mafic 3. felsic 4. ultramafic

mafic

A __________ is a volcanic hazard arising from a collapsing eruption column that runs downhill at high speeds (>100 mph). These are associated with explosive eruptions and a mix of lava lapilli, pumice, ash, and hot gases. 1. lapilli flow 2. rain composed of acid 3. pyroclastic flow 4. ash and lahar flow

pyroclastic flow

Examine Bowen's Reaction Series diagram. As a felsic magma cools, which mineral would be the last to crystallize? 1. quartz 2. biotite 3. muscovite 4. k-spar 5. olivine

quartz

Examine Bowen's Reaction Series diagram. If a rock contains amphibole, potassium feldspar (orthoclase), and quartz, if the rock is heated, which mineral would melt first? 1. amphibole 2. quartz 3. • None. The melting point of these can't be reached 4. potassium feldspar (orthoclase)

quartz

The largest type of volcano is called a _______ volcano and is characterized by broad, low-angle flanks, a small vent or groups of vents at the top, and basaltic magma. 1. lava dome 2. shield volcano 3. stratovolcano (composite cone) 4. caldera 5. cinder cone

shield volcano

What kind of volcanoes make up the Hawaiian Island Chain? 1. stratovolcanoes 2. shield volcanoes 3. cinder cones 4. calderas 5. lava domes

shield volcanoes

A _______ volcano has steep flanks, symmetrical cone shapes, distinct crater at the top, and a silica-rich magma that results in an explosive eruption style. 1. stratovolcano (or composite volcano) 2. flood basalt 3. caldera 4. shield volcano 5. cinder cone

stratovolcano (or composite volcano)