Week 5

Question 1

Decompression melting

Answer 1

Melting that occurs as rock ascends due to a drop in confining pressure

Question 2

Addition of volatiles

Answer 2

Lowers melting temperature

Question 3

Increased temperature

Answer 3

Causes melting

Question 4

Bowen’s reaction series

Answer 4

A concept by Bowen that illustrates the relationships between magma and the minerals crystallizing from it during the formation of igneous rocks

Question 5

Magmatic differentiation

Answer 5

The process of generating more than one rock type from a single magma

Question 6

Crystal setting

Answer 6

A process that occurs during the crystallization of magma in which earlier formed minerals are denser than the liquid portion and settle to the bottom of the magma chamber

Question 7

Dike

Answer 7

A tabular shaped intrusive igneous figure that cuts through the surrounding rock

Question 8

Sill

Answer 8

Intrusive deposit. A tabular igneous body that was intruded parallel to the layering of preexisting rock

Question 9

Pluton

Answer 9

Magma displaces rock, the solidified magma structures that result from this are intrusions (plutons)

Question 10

Batholith

Answer 10

Extrusive, a large mass of igneous rock that formed when magma was emplaced at depth, crystallized, and subsequently exposed by erosion

Question 11

Explain the process of decompression melting

Answer 11

As hot mantle rock goes up, it moves into zones of lower pressure. The drop in pressure initiates decompression melting.

Question 12

What role does water and other volatiles play in the formation of magma

Answer 12

They act as salt does to melt ice. Water causes rock to melt at lower temperatures. This happens mainly at convergent plate boundaries( cool oceanic lithosphere sink, heat and pressure drive water from it and brings it to the wedge of the mantle, making it hotter and leads to melting

Question 13

What 3 locations (in class) that magma will form

Answer 13

Midocean ridge
Subduction zones
Mantle plumes

Question 14

Describe the process of crystal settling

Answer 14

Earlier formed minerals are denser than the liquid portion and sink to the bottom of the magma chamber(makes the result richer in sodium potassium and silica

Question 15

Process of magmatic differentiation

Answer 15

When the remaining melt solidifies, if it migrates into surrounding rock it will form a rock with mineral composition

Question 16

Process of assimilation

Answer 16

Rocks get into the magma and their composition does as well

Question 17

Process of magma mixing

Answer 17

2 chemically different magma bodies are going up and the more buoyant may rise faster. They eventually join and mix and the two masses blend

Question 18

3 ways magma will form

Answer 18

1. Decrease in pressure (no increase in temp)-decompression
2. adding water
3. Heating is crustal rocks above melting temp

Question 19

Viscosity

Answer 19

Fluids resistance to flow

Question 20

Volatile

Answer 20

Gaseous components of magma dissolved in the melt. Ready to vaporize at surface pressures

Question 21

Aa

Answer 21

Lava flow that has a jagged blocky surface

Question 22

Pahoehoe

Answer 22

Lava flow with a smooth to ropy surface

Question 23

Block lavas

Answer 23

Lava that has a surface of angular blocks associated with material having andesitic and rhyolitic composition

Question 24

Pyroclastic materials

Answer 24

Volcanic rock ejected during an eruption. Includes ash bombs and blocks

Question 25

Fissure

Answer 25

A crack in a rock along which there is a distinct separation

Question 26

Vent

Answer 26

Surface opening at a conduit or pipe

Question 27

Summit and flank

Answer 27

I

Question 28

Crater

Answer 28

The depression at the summit of a volcano or a depression that is produced by a meteorite impact

Question 29

Shield volcano

Answer 29

BASALTIC. Starts on the ocean floor Broad gently sloping volcano built from fluid basaltic lavas. Tend to form at hot spots. Decompression melting, increased temperatures

Question 30

Composite cone volcano

Answer 30

Erupts big Volcano composed of both lava flows and pyroclastic material

Question 31

Cinder cone

Answer 31

ANDESITIC. Rather small volcano built primarily of ejected lava fragments that consider mostly pea to walnut sized lapili,

Question 32

Pyroclastic flow

Answer 32

Highly heated mixture, largely of ash and pumice fragments that travels down the flanks of a volcano or along the surface of the ground

Question 33

Lahar

Answer 33

Debris flow on the slopes of a volcano that results when unstable layers of ash and debris become saturated and flow downslope, usually following steam channels

Question 34

Tsunami

Answer 34

Japanese word for seismic air wave

Question 35

Caldera

Answer 35

Large depression typically caused by collapse or ejection of the summit area of a volcano

Question 36

Flood basalt

Answer 36

Flows of basaltic lava that issue from numerous cracks or fissures and commonly cover extensive areas to thickness of hundreds of meters

Question 37

Define viscosity and 3 factors that influence it

Answer 37

Resistance to flow 1. temperature (lower temp) 2. composition (more silica) 3. Dissolved gasses (less gas)

Question 38

List the 3 magmas basaltic andesitic and rhyolitic in order most to least silica

Answer 38

Rhyolitic -most (felsic) 70 Andesitic-middle Basaltic- least (mafic) 50

Question 39

Compare and contrast aa and pahoehoe

Answer 39

Aa: rough jagged sharp, hard to cross Pahoehoe: smooth, twisted braid, means “one can walk

Question 40

List main gases released during a volcanic eruption. What role do they play in the eruption?

Answer 40

``` 70% water vapor 15 carbon dioxide 5 nitrogen (Contribute to the atmosphere) Gas rich magma produces ash, causes it to be explosive like a wine bottle ```

Question 41

What are pyroclastic materials: 3 examples

Answer 41

Pulverized rock, lava, and glass fragments from eruptions 1. ash: 2. Lapili: 3. Volcanic bombs

Question 42

Crater vs caldera

Answer 42

Crater is a funnel shaped depression (bowl) | Caldera is a large circular depression

Question 43

Distinguish conduit and vent

Answer 43

The circular path that the magma makes is a condiut, it goes into a surface opening called a vent

Question 44

Describe composition and viscosity of shield volcano lava

Answer 44

Basaltic, low viscosity

Question 45

Where do most shield volcanoes form?

Answer 45

Ocean floor

Question 46

Composition of a cinder cone

Answer 46

Made up entirely of pyroclastic material/ fragments, often basaltic

Question 47

How does size and steepness of a cinder cone compare with a shield volcano

Answer 47

Cinder cones are much steeper

Question 48

Where do most composite cone volcanos form

Answer 48

Ring of fire (Pacific Ocean)

Question 49

What kind of pyroclastic material result from composite cone eruption

Answer 49

Materials with a felsic composition , High viscosity

Question 50

What is the difference between a lahar and a pyroclastic flow

Answer 50

Pyroclastic:Hot glowing ash and large lava fragments, Lahar: cooled at surface, a fluid mud flow when debris becomes saturated with water

Question 51

3 ways magma will evolve

Answer 51

Crystal settling Assimilation Magma mixing

Question 52

Magma always starts as ____

Answer 52

Mafic

Question 53

Mafic/ felsic high or low viscosity

Answer 53

Mafic low | Felsic high

Question 54

What texture is basalt

Answer 54

Aphanitic

Question 55

Where do basaltic plateaus form

Answer 55

Continental rift zones