Geology 101 Quiz 4 Flashcards
knowledge of rock properties can help determine things like
where it is dangerous to build, whether a groundwater contaminant will migrate off site, what is the best material for making buildings or highways
understanding earth processes can help determine things like
where to expect earthquakes, where to dig for gold or oil, how to make synthetic rubies and diamonds, why a lake in Africa discharged a CO2 cloud that killed hundreds
three basic rock types
igneous, sedimentary, metamorphic
igneous rocks
formed by solidification from magma
sedimentary rocks
formed by accumulation and lithification of existing mineral grains OR precipitation of dissolved ions from water
metamorphic rocks
formed by alteration of existing rocks under high temperature and/or pressure
lithification
the process of turning sediments into rock
weathering
physical breakage and chemical decomposition of rocks (including dissolution)
erosion
transport of weathered rock away from point of origin
rock cycle
rocks are generally thought of as eternal; rocks can be “recycled,” where one rock can be broken down or altered and turned into a different type of rock
igneous rock -?-> weather erode
uplift
weather erode -?-> sedimentary
deposition, burial, lithification
sedimentary -?-> weather erode
uplift
sedimentary -?-> metamorphic
heat pressure
metamorphic -?-> weather erode
uplift
metamorphic -?-> igneous
melt, cool, solidify
igneous -?-> metamorphic
heat, pressure
sedimentary cannot go straight to ? and why
igneous; a sedimentary rock will form a metamorphic rock prior to melting
?, or texture of an igneous rock, was used to classify igneous rocks before it was really understood why it varied so much
crystal size
the primary clues to what causes crystal size to vary in igneous rocks came from studying ?
volcanic lava flows (since the flows started as magma and solidified to form igneous rocks)
if a section of cooled lava was broken open, several observations could be made:
large crystals are never observed in lava; of the small crystals present, the larger crystals are always found near the base or middle, never at the top
what suggested that time must play a role in igneous rock crystal size?
the top of the lava flow cools the fastest and the interior cools slowly
igneous rocks: the slower the cooling rate, the more time atoms have to ?
align themselves to grow larger crystals
since lava flows always produce small crystals, igneous rocks with large crystals must have formed where?
beneath the surface where cooling rates could be very slow
the presence of ? in magma also facilitates larger crystal growth
water
two categories of igneous rocks
intrusive, extrusive
intrusive igneous rock
magma intruded into existing rock and solidified beneath the surface
extrusive igneous rock
magma extruded to the surface (lava) and solidified on the ground
igneous rocks are classified using two different systems based on either ? or ?
the occurrence of the rock (where found and in what form) or the composition of the rock (what minerals it is made from)
pluton
large igneous body formed at depth
batholith
large pluton
stock
smaller pluton
plutons form in different ways, but all ways start with
magma that begins to rise (because it is less dense than solid rock)
the simplest way a pluton forms is by simply
melting its way upward