Geosphere- Rock Cycle Pt 1

Question 1

rocks=

Answer 1

naturally occurring mixtures of minerals plus non-mineral material like organic matter and volcanic glass

Question 2

rocks are classified into 3 groups:
1. ____=
2. ____=
3. _____=

Answer 2

igneous= formed from the cooling of molten magma

sedimentary= deposited on the surface of the geosphere by the atmosphere, hydrosphere, or biosphere

metamorphic= originally igneous or sedimentary rocks that’ve formed new minerals under heat and/ or pressure in the solid state (no melting!)

Question 3

magma is any ___ rock

magma that reaches the surface is ___

Answer 3

molten (fully or partially melted)

lava

Question 4

single minerals melt at a ____ temperature for a given ___
- How can the melting point be lowered?

Answer 4

fixed temp for a given pressure

add water! (a small amount of water makes a huge difference)

Question 5

mixtures melt over a range of temps:
- solidus=
- partial melting=
- liquidus=

Answer 5

solidus= start of melting

partial melting: b/c each mineral contained in a certain rock has a diff melting point, some parts of the rock will melt sooner = partial melting

liquidus= complete melting

Question 6

partial melting produces a magma with different composition from the ___ rock

Answer 6

parent (starting rock)

Question 7

what are 2 ways to melt dry rock? (for example, mantle peridotite)
1
2

Answer 7

1. reduce the pressure adiabatically (without losing or gaining heat)
2. add water

Question 8

To melt wet rock (for example, crustal rocks), ___ the ____

Answer 8

increase the pressure

Question 9

T/F
hot magma from the mantle can melt crustal rocks on its way to the surface

Answer 9

true
this is the advection of heat

Question 10

____ is the most abundant element in igneous rocks.
Does it exist like it does in the atmosphere?

Answer 10

oxygen

no! It’s bonded to other things, most often Si (SiO2)

Question 11

___ is the most abundant component of almost all magma and igneous rocks
- What does it tell us?

Answer 11

SiO2 (silica)
how silica varies tells us about how the rock formed

Question 12

___ ___ is used to classify igneous rocks

Answer 12

silica content (SiO2 varies!)

Question 13

tephra=

Answer 13

explosive eruptions produce fragments called tephra

Question 14

pyroclastic rock is a ____
What’s the analogy for these explosive eruptions?

Answer 14

tephra

analogy: shake a pop can then open it- the foam= the fragments of rock (tephra)

Question 15

When there’s a volcanic eruption from the sea floor, what’s the typical shape of (cooled) magma that has erupted underwater? What’s it called?

Answer 15

There will be huge chunks of “boulders” that are actually sections of the seafloor that’ve erupted out

these sections have a bunch of small boulders in them, which is the typical shape when magma erupts underwater
This is called Pillow basalt

Question 16

What is a fissure eruption?

Answer 16

when magma reaches the surface through fractures in the crust

Question 17

What’s associated with cinder/ tephra cones?

Answer 17

very explosive magma- releases volatiles as it erupts

• lots of pyroclastic material/ tephra

Question 18

shield volcanoes are a large ____ of lava flows

Answer 18

buildup
- built by lava that’s low viscosity (builds up by successive flows over time)
- eg Hawaiian islands

Question 19

what is the behavior of felsic and intermediate magmas?

Answer 19

they’re very viscous (sticky): gases can’t escape so they come out all at once in an eruption
- very explosive
- large amounts of tephra (pyroclastic flows)

Question 20

____ blasts and ___ flows are characteristic of tephra eruptions

Answer 20

lateral blasts and pyroclastic flows

Question 21

How do caldera eruptions happen?
Give an example of one

Answer 21

• there is lots of magma fairly close to the surface
• some magma escapes through an eruption column, so there is less magma underneath
• the top of the partially empty magma chamber collapses
• magma can explode out of the openings on the side now= pyroclastic flows out both sides

eg. crater lake: was once Mount Mazama before it erupted and collapsed

Question 22

What are 4 things that are caused from large scale eruptions that make it very high into the atmosphere?

Answer 22

• reduced solar radiation (temporary- due to ash)
• temp drops b/c of SOx aerosols= earth cooling (longer term)
• immediate intense precipitation
• Lahars (mudflows) because of this precipitation

Question 23

Explain what happened with the Tambora eruption in Indonesia (1815)

Answer 23

huge eruption- material made is very high in atmosphere
- N hemisphere experienced “year without summer”
- widespread crop failures, famine, disease due to temp drop (SOx particles in air, reduced solar radiation)

Question 24

Volcanic eruptions may have been the culprit for the ___ extinction (250 million years ago). What are 2 possibilities?

Answer 24

Permian

1. Extensive periods of volcanism
   - climate deteriorated
   - eg mafic magma in siberia
2. Or just a few really big eruptions
   - for example, Toba (caldera in Indonesia) coincident with a 1000yr climate cool cycle