Intro to rocks Flashcards
1.10-1.14
rock defintion
a coherent naturally occurring solid that’s consists of an aggregate of minerals or less commonly a body of glass
define coherent
holds together on its own and must be broken in order to separate into smaller pieces
do unnatached mineral grains consitute a rock
no
Two main types of rocks
crystalline and clastic
crystalline rock are
rocks whose grains interlock with one another like a puzzle
granite (clast or cryst)
crystalline
crystalline rocks grew
when an igneous melt solidified
clastic rocks are
rocks that consist of separate grains that have been cemented together
natural cement is composed of
minerals that have precipitated from water
sandstone (clast or cryst)
clastic
Grain vs crystal are _ when talking about rocks
interchangable
grain defintion
mineral crystal in a rock or a fragment that has broken of either another rock or larger piece of mineral and has since almagamated forming another rock
we will use the term crystal only when
referring to a piece of a single mineral that displays faces
glass rock example
obsidian
glass rock
either originated as a continuos mass or formed through the welding together of individual glass grains when they where still hot
Three rock study scales
Hand sample
outcrop
thin section
Hand sample
medium scale
what we do in labs
outcrop
large scale
identifies basic rock types
thin section
petrographic microscope
used to identify compostion
High tech equipment is
more accurate but expensive
2 forms of surface rocks
fragmented chunks
bedrock
broken chunks or fragments are
pebbles cobbles or boulders
“clasts”
broken off bedrock by wind water ice or gravity
can be transported from source
bedrock is
attached to the earths crust
surface exposure is outcrop
good for building on
3 PRIMARY TYPES OF ROCKS
igneous
sedimentary
metamorphic
igneous rocks form from
molten material
two types of igneous (where they cooled) also third type
extrusive
intrusive
volcanic debris
igneous etymology
latin ignis for fire
sedimentary rocks are
loose classes that were broken off pre existing rock
or by the precipitation of mineral crystals in water
always formed at or near earths surface
sedimentary rocks contain layers that
represent different periods of deposition and leave a detailed record of surface history
metamorphic rocks from when
pre existing rocks change character in specific temperature pressure conditions
metamorphic rocks can form from
sedimentary or igneous rocks
metamorphic rocks form in what conditions
high temperature and pressure at extreme depth while still in solid state
metamorphic rocks undergo chemical changes through
dissolution
physical changes in metamorphic rocks include
squashing, stretching, or sheering
define protolith
parent of a metamorphic rock
upper temp limit to form metamorphic rocks
rock can not melt
grades of metamorphic rock ranges from
high to low
grains come in a wide range of
sizes
equant grains are
same dimension in all directions (roughly ball shaped, but still could be angular)
inequant grains are
not the same in all directions (look like poop)
a grain can be a crystal or a
clast
composition refers to
the proportions of different chemicals that make up a rock
chemical composition alone
does not control the assemblage of minerals in a rock
texture refers to
the configuration of grains in a rock
texture relies on
composition and grain shape
igneous textures include
crystalline, fragmental, glassy
layers in sedimentary rocks is
bedding
layers in metamorhpic rocks is
foliation
bedding is
separate layers of deposition over time
foliation is
the arrangement of minerals in the rock brought on by physical and chemical changes
the rock cycle is
the progressive transformation of earth materials from one rock type to another over time
sedimentary goes to metamorphic through
burial and heating
metamorphic goes to igneous by
melting
igneous goes to sedimentary by
erosion transportation and deposition
sedimentary goes to igneous by
heating and melting
metamorphic goes to sedimentary by
erosion ,transportation and deposition
igneous goes to metamorphic by
burial and or heating
sedimentary goes to sedimentary by
erosion, transportation and redeposition
metamorphic goes to metamorphic by
burial heating and remetamorphism
igneous got to igneous by
heating and remelting
new melt enters crust from the
mantle
material returns to the mantle by
subduction