Lecture 8 Minerals and Rocks 6

Question 1

how do metamorphic rocks form

Answer 1

rocks formed when heat,
pressure and/or chemica; changes alter original/parent rocks, generating completely new rocks

Question 2

do parent rocks melt

Answer 2

NO, otherwise an igneous rock would be formed

Question 3

what can parent rocks be

Answer 3

sedimentary, igneous or even at times another metamorphic rock

Question 4

what does the greek word for metamorphic mean

Answer 4

“to change from”

Question 5

what are the 3 agents of metamorphism

Answer 5

• increased temperature
• increased pressure
• chemical changes

Question 6

increased temperature

Answer 6

• encountered when sediment/rock layers find themselves buried deeper and deeper in the ground due to added sediment/rock layers above them
• as descend into Earth, temperatures increase at
  approximately 25oC per kilometer
• deeper our rock layer of interest descends, the hotter
  temperatures become, allowing for metamorphism

Question 7

what does the weight of sediment/rock layers piling on to layer of interest also
cause

Answer 7

increase in pressure

Question 8

does temp increase or decrease at subsuction zones

Answer 8

increased temperture at subduction zones (where one tectonic plate descends below the other)

Question 9

at subduction zones

Answer 9

• intense friction between tectonic plates results in heat/increased temperatures
• some of rock on descending plate will melt, ultimately forming igneous rock
• rock adjacent to/next to this hot molten/melted rock or magma will heat up,
  but not melt, thus forming metamorphic rock
  NOTE: here too, there is also intense pressure

Question 10

what does the yellow region in a scketch demonstrate

Answer 10

demonstrates where metamorphic rock would form at a subduction zone, adjacent to/next to molten/melted rock or magma

Question 11

pressure can increase due to

Answer 11

• huge weight of sediment/rock layers forming above our rock layer of interest
• collision of tectonic plates (at
  convergent plate boundaries).
• high friction caused by sliding of tectonic plates past one another (at transform plate boundaries)

Question 12

what happens as a layer of sedimentary/rock is added above a rock layer

Answer 12

pressure increases

Question 13

chemical changes can occur when

Answer 13

• hot fluids and vapors/gases present at high temperature and high pressure sites fill pores of existing rocks.
• fluids/vapors/gases can trigger chemical reactions or leave behind minerals that ultimately change chemical composition/make up of parent/pre- existing rock.

Question 14

how is wollastonite formed and what is its chemical formula

Answer 14

wollastonite = CaSiO3

a chemical reaction convertring 2 minerals (quartz and calcite) into a new silicate mineral (wollastonite)

Question 15

how long can metamorphism take

Answer 15

metamorphism (formation of
metamorphic rock) can occur almost instantaneously at tectonic plate boundaries or take millions of years deep below Earth’s surface.

Question 16

characteristics of metamorphic rocks

Answer 16

• typically harder than sedimentary parent rocks
• as hard or harder than igneous parent rock
• form roots of mountains chains, becoming exposed to Earths surface when softer layer of rock above them weathered/eroded away

Question 19

what does sedimentary parent rocks SHALE (mudstone) become

Answer 19

metamorphic rock slate

Question 20

what’s special about layers of shale

Answer 20

they become buried deeper and deeper in the ground
- due to increased number of sediment/rock layers above
- temperature and pressure increase
thus slate is formed

Question 21

how can slate split and why is that important

Answer 21

slate can split into perfectly thin sheets
- it has a perfect cleavage
- can be used as a building material (for roofing)

Question 22

what is schist

Answer 22

a metamorphic rock that can form from the transformation of various silicates minerals, including mica, hornblendes and talc

Question 23

what is gneiss

Answer 23

• metamorphic rock with distinct “banding” /layers
• different layers observed in “banding” correspond to different minerals
• like granite (its parent igneous rock), it consists primarily of feldspars, mica, and quartz (minerals)
• can also come from parents igneous rock rhyolite, the extrusive equivalent of intrusive granite

Question 24

what does gneiss and granite both consist primarily of

Answer 24

• feldspar
• mica
• quartz
  (minerals)

Question 25

what is quartzite

Answer 25

a metamorphic rock formed from sandstone that has come into contact with deeply buried magma

Question 26

what is marble

Answer 26

• comes from sedimentary parent rocks limestone (and dolostone)
• often white in color, can come in any different colours (such as black, red, gray pink) due to impurities
• slightly harder than parent sedimentary rocks
• used as a building material

Question 27

what is michelangelo’s “david” made of

Answer 27

marble

Question 28

when did birds first appear

Answer 28

Jurassic Period