Lecture 4 - Mineral and Rocks 2 Flashcards
what are the two categories of igneous rock
intrusive and extrusive
how do intrusive igneous rock form
when magma trapped below surface cools slowly, solidifying over thousands or millions of years
how do extrusive igneous rock form and what’s its other name
volcanic igneous rock
forms when magma/lava exits a volcano or rises up to the surface through a fissure
what is the most important component of igneous rock and why
SiO2 — Silica content
silica accounts for nearly half or more of the mass/weight of igneous rock form
how does silica content in igneous rock go back to volcanoes
magma (and lava) from statrovolcanoes is:
- very viscous (sticky)
- rich in silica
magma (and lava) from shield volcanoes is:
- rich in iron and magnesium
- does not contain much silica
- less sticky
how do you classify magma/lava
as either felsic or mafic
- depending on silica content
what happened with Mount Tambora
- Place
- Type of volcanoes
- Year
- what do they call the year after + why
- what happened
- Indonesia
- Stratovolcano, on subduction zone
- 1815: largest eruption in recorded history
- 1816: referred to as “year without summer” due to volcanic airborne material in atmosphere blocking sunlight
- temperatures dropped and crops failed, leading to food shortages in the Northern Hemisphere
Characteristics of felsic magma/lava
- higher viscosity (stickier)
- less iron (Fe)
- richer in silica (SiO2)
- found near subduction zones
Characteristics of mafic magma/lava
- lower viscosity (less sticky)
- richer in ion (Fe)
- less silica (SiO2)
- found at hot spots and mid-ocean ridges
What type of magma (felsic or magic) does a stratovolcano on subduction zone create + example
Felsic magma/ lava rich in silica
Great Sitkin Volcano (Aleutian Islands, Alaska)
What type of magma does Mount Kilauea create
Hot spot volcano
Mafic lava containing less silica
if igneous rock greater than 65% silica what does it become
felsic
what do felsic igneous rocks include
rhyolite and granite
if igneous rock 55-65% silica what does it become
intermediate
what does intermediate igneous rocks include?
andesite and diorite
if igneous rock 45-55% silica, what does it become
mafic
what do mafic igneous rocks include
basalt and gabbro
if igneous rock less than 45% silica, what does it become
ultramafic
what do ultramafic igneous rocks include
peridotite
rank the order, lightest + less dense to darker and denser out of the three fine-grained extrusive (volcanic)
rhyolite (felsic) — andesite (intermediate) — basalt (mafic)
rank the order, lightest + less dense to darker and denser out of the three coarse-grained intrusive
granite (felsic) — diorite (intermediate) — Gabbro (mafic)
this order also represents a decrease in silica and an increase in iron
what does it mean if an extrusive igneous rock has a intrusive equivalent and vise versa
the process by which they form, and appearance differs, their content/composition is very comparable
basalt is the extrusive equivalent of..
intrusive gabbro
andesite is the extrusive equivalent of..
intrusive diorite
rhyolite is the extrusive equivalent of…
intrusive granite
what is granite
intrusive felsic
what is rhyolite
extrusive felsic
diorite
intrusive intermediate
gabbro
intrusive mafic
basalt
extrusive mafic
andesite
extrusive intermediate
which is typically lighter out of the intrusive or extrusive equivalents
intrusive is typically lighter than extrusive equivalents
what are the characteristics of sulfur (S)
- an element (16 protons) and a mineral
- has a distinctive yellow colour and odour
- melts at a low temperature (108C)
- it has a low density (approximately 2 grams/cubic centimeter or 2 grams/millimeter) and therefore feels “light”
how many naturally occurring minerals are there on earth
4000
minerals form when…
- magma cool
- water rich in molecules that make-up minerals evaporates, allowing the molecules to crystallize (this is what occurs in underground caves)
mineral crystals can be… (in terms of size)
- small if form in confined spaces (ex: between other solids/other minerals)
- larger if given necessary time and space (ex: within geodes)
what is stalagmite
upwards growing mound of mineral deposits (often CaCO3) that originated in water that dripped onto cave floor
what is stalactite
icicle-shaped formations/mineral deposits that hang form ceiling of a cave
what can stalagmites and stalactites contain
may contain other materials such as lava and even amberat which crystallized pack rat urine
what is amberat
crystallized pack rat urine!
what are geodes
hollow rock formations with minerals that have developed inside
what mineral often develops inside a geode
quartz crystal
SiO2
geodes can form when…
- material around a hollow in the ground (ex: animal burrow) turns to rock
- gas bubbles/pockets are found inside igneous rock/when lava cools around gas bubbles/pockets
what do pockets in geodes do
they allow for water to seep in
what happens over time with geodes
over time, water evaporates, leaving behind molecules that make up minerals. molecules crystallized forming mineral crystals
how long does it take for crystals within pockets to form + what does a bigger crystal often mean (geodes)
thousands/millions of years, with the largest crystals typically being the oldest
why are the quartz crystals different colours
- because of elemental impurities
- precedes of additional elements/impurities in mineral crystals can give them variety of colours
iron (Fe) turns a mineral crystal which colour?
red or purple
titanium (T) turns a mineral crystal which colour?
bue
Nickel (Ni) turns a mineral crystal which colour?
green
Manganese (Mn) turns a mineral crystal which colour?
pink
how can minerals be classified
- chemical composition
- properties
- crystal systems
how many mineral classes are there ( + how many were there originally)
78
originally: 9 (known as Dana Classification System)
what is the name of the mineral classification system that has only 9 classes
Dana Classification System
native elements (mineral class)
singular elements existing on their own such as sulfur (S) or copper (Cu)
sulfides (mineral class)
minerals containing sulfur ions (S2-) and other elemtents
sulfates (mineral class)
minerals containing sulfatge ions (SO42-) and other elements
halides (mineral class)
minerals containing chlorine (Cl-) or fluorine (F-) ion and other elements
oxides (mineral class)
minerals containing oxygen atoms (O) or ions (O2-) and other elements
carbonates (mineral class)
minerals containing carbonate ions (CO32-) and other elements
phosphates (mineral class)
minerals containing phosphate ions (PO43-) and other elements
silicates (mineral class)
minerals containing silicon combined with oxygen in various ways
what is the chemical formula of Copper and what is it considered
Cu — mineral
what is the chemical formula of Galena and what is it considered
PbS — a sulfide
what is the chemical formula of Aragonite and what is it considered
CaCO4 — a carbonate
what is Turquoise considered
a phosphate
silicates are divided into
subgroups (because its such a big group)
organics (mineral class)
not true minerals
- contains materials such as amber which comes from trees and amberat, which comes from pack rats
-they are not true minerals since they are organic
- organic minerals contain Carbon (C), more specifically carbon-hydrogen bonds and may come form previously living beings
