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Geology > Week 5 > Flashcards

Week 5 Flashcards

1
Q

Decompression melting

A

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

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2
Q

Addition of volatiles

A

Lowers melting temperature

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3
Q

Increased temperature

A

Causes melting

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4
Q

Bowen’s reaction series

A

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

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5
Q

Magmatic differentiation

A

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

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6
Q

Crystal setting

A

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

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7
Q

Dike

A

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

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8
Q

Sill

A

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

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9
Q

Pluton

A

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

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10
Q

Batholith

A

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

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11
Q

Explain the process of decompression melting

A

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

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12
Q

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

A

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

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13
Q

What 3 locations (in class) that magma will form

A

Midocean ridge
Subduction zones
Mantle plumes

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14
Q

Describe the process of crystal settling

A

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

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15
Q

Process of magmatic differentiation

A

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

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16
Q

Process of assimilation

A

Rocks get into the magma and their composition does as well

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17
Q

Process of magma mixing

A

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

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18
Q

3 ways magma will form

A
  1. Decrease in pressure (no increase in temp)-decompression
  2. adding water
  3. Heating is crustal rocks above melting temp
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19
Q

Viscosity

A

Fluids resistance to flow

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20
Q

Volatile

A

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

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21
Q

Aa

A

Lava flow that has a jagged blocky surface

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22
Q

Pahoehoe

A

Lava flow with a smooth to ropy surface

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23
Q

Block lavas

A

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

24
Q

Pyroclastic materials

A

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

25
Q

Fissure

A

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

26
Q

Vent

A

Surface opening at a conduit or pipe

27
Q

Summit and flank

A

I

28
Q

Crater

A

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

29
Q

Shield volcano

A

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

30
Q

Composite cone volcano

A

Erupts big Volcano composed of both lava flows and pyroclastic material

31
Q

Cinder cone

A

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

32
Q

Pyroclastic flow

A

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

33
Q

Lahar

A

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

34
Q

Tsunami

A

Japanese word for seismic air wave

35
Q

Caldera

A

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

36
Q

Flood basalt

A

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

37
Q

Define viscosity and 3 factors that influence it

A

Resistance to flow

  1. temperature (lower temp)
  2. composition (more silica)
  3. Dissolved gasses (less gas)
38
Q

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

A

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

39
Q

Compare and contrast aa and pahoehoe

A

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

40
Q

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

A 
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
41
Q

What are pyroclastic materials: 3 examples

A

Pulverized rock, lava, and glass fragments from eruptions

  1. ash:
  2. Lapili:
  3. Volcanic bombs
42
Q

Crater vs caldera

A

Crater is a funnel shaped depression (bowl)

Caldera is a large circular depression

43
Q

Distinguish conduit and vent

A

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

44
Q

Describe composition and viscosity of shield volcano lava

A

Basaltic, low viscosity

45
Q

Where do most shield volcanoes form?

A

Ocean floor

46
Q

Composition of a cinder cone

A

Made up entirely of pyroclastic material/ fragments, often basaltic

47
Q

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

A

Cinder cones are much steeper

48
Q

Where do most composite cone volcanos form

A

Ring of fire (Pacific Ocean)

49
Q

What kind of pyroclastic material result from composite cone eruption

A

Materials with a felsic composition , High viscosity

50
Q

What is the difference between a lahar and a pyroclastic flow

A

Pyroclastic:Hot glowing ash and large lava fragments,

Lahar: cooled at surface, a fluid mud flow when debris becomes saturated with water

51
Q

3 ways magma will evolve

A

Crystal settling
Assimilation
Magma mixing

52
Q

Magma always starts as ____

A

Mafic

53
Q

Mafic/ felsic high or low viscosity

A

Mafic low

Felsic high

54
Q

What texture is basalt

A

Aphanitic

55
Q

Where do basaltic plateaus form

A

Continental rift zones

Geology (12 decks)

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