Test 1 Flashcards
What are minerals
-Naturally occuring
-Solid
- Ordered internal molecular structure
-Definite chemical composition
minerals found in granite
Quartz
Hornsblend
feldspar
Process Resulting in formation of minerals
-Precipitation of minerals from solution
-Crystallization of molten rock
-biological processes
what determines crystalline structure?
Ionic Size
and
charges of ions
Polymorphs
minerals with the same composition but different crystalline structures
ex: diamonds and graphite
Physical properties of Minerals
Crystal form, luster,color, streak, hardness, cleavage, fracture, gravity (Density)
Crystal form
external expression of internal structures
Luster
if it reflects light
color
an unreliable mineral identifier
Streak
color of the minerals powder form
Hardness
resistance to scratching
cleavage
how it breaks resulting on different flat planes
fracture
absence of cleavage
Gravity(density)
weight of a mineral
major mineral groups
-Silicates
-Carbonates
-oxides
-sulfides
-sulfates
-native elements
-phosphates
Silicates
most important because of its abundance of Silicon and oxygen, earth consists of 92% of silicates
Mafic minerals
Olivine
pyroxene
aphibole
biotite
felsic Minerals
Muscovite
Plagioclase
Orthoclase
Quartz
Mafic
Dark colors
simple structures
felsic
Light colors
complex structures
Magma
Completely or partially molten rock composed of melt, solids, volitiles
Melt
liquid portion of magma made up of Oxygen, and silicon
Solids (magma)
Minerals that crystallized
Volatiles
Water vapor, carbon dioxide, sulfur dioxide
crystallization
Precipitation of mineral grains from magma
Igneous textures are controlled by what?
-Rate at which magma cools
- The amount of dissolved gases present
-amount of silica present
rate of which magma cools
slow cooling, results in larger crystals and fewer nucleation
rapid cooling, results in many small crystals
Aphanitic/Vesicular texture
Individual crystals too small to see by the naked eye
Phaneritic
Individual crystals large enough to see
porhyritic
Large crystals in a fine grained crystals
glassy
Lacks crystalline structure because of rapid cooling
Pegmatitic
abnormally large crystals
Mafic minerals composition
High in Iron, and magnesium low in silicon
Felsic minerals composition
low in Iron, and magnesium, high in Silicon, Calcium, Potassium, and Sodium
Obsidian
Felsic, just glass
Pumice
glassy, formed by large amounts of gas, usually felsic
Pyroclastic
Rock composed of fragments ejected during eruption
Origin of magma
originates when solid rock in mantle and crust melts
Geothermal gradient
the rise in temp with depth in the earths crust
20-30 C/km
Melting curve
minimum temperatures at specific depths required to melt a rock
process aiding in melting
Decrease in pressure
Introduction of volatile’s
increase in temp (not common)
Decompression melting
Melting of rocks occurs at lower temperatures with decreasing depth
Volatiles
addition of volatile’s (water) to decrease melting temp : wet melting
Magmatic Differentiation
seperation of a melt from earlier formed crystals, also called frational crystallization changing magma from mafic to felsic
Crystal settling
dense early formed minerals settle to the bottom of a magma chamber remaining melt
magmatic assimilation
changing a magma’s composition by incorporation of surrounding rock bodies
Magma mixing
two chemically distinct magmas mixed to produce a composition different from original magma
Partial Melting
Rock heated the minerals with lowest melting temp melts first
igneous activity at Divergent margins
-Asthenosphere rises at spreading centers
-cause decompression melting
-forms mafic magma
Igneous activity at convergent margins
-Subduction drags oceanic lithosphere
-release of volatiles in subduction zone lowering the melting point of adjacent mantle
-causes wet melting of the mantle to form a mafic magma
Viscosity controlled by?
-Silicon content
-dissolved gasses
-temprature
When pressure decreases
dissolved gases are released and form bubbles in magma
Low viscosity (low Si)
allows gases to migrate upwards and escape causing passive eruption
high Viscosity(High Si)
Traps gases until enough pressure builds causing violent ejection of gas and magma
Pahoehoe
lava flow looks like braids
Ah-ah
lava flow is jagged and blocky
Volcanic gases
70-H20
15 -CO2
5-N
5-SO2
Pyroclastic material
Material ejected from volcanic explosion
air fall
fragments ranging in size ejected from volcanoe
Lahar
Volcanic ash mud flow
Types of volcanoes
Shield Volcano, Cinder Cone, Composite Volcano
Shield Volcano
-largest in size
-gentle sides
-long duration of activity
-non violent eruptions
-long eruptions
-Mafic lava
Cinder Cone
-Mafic lava
-Formed mainly of basaltic pyroclastic material
-steep
-small
-short life span
-isolated or on other volcanoes
composite volcano
- pyroclastic, and andesitc lava flows
-intermediate steepness
-average size
-span 1k years
-violent
Lava Dome
Steep sided dome formed from viscous felsic lava , small
calderas
large circular depressions from collapsed volcanoes
Basaltic plateaus
massive accumulations of basaltic magma covering thousands of miles ( associated with extinction)
How volcanoes effect climate change
explosion emits huge quantities of ash into atmosphere
-portion of incoming solar radiation is reflected
-short term cooling
Plutons
Igneous structures that cooled and crystallized beneath the earths surface based on shape and orientation
Orientation
with respect of surrounding rock
Batholith
Massive discordant pluton
Laccolith
concordant, tabular pluton warping surrounding rocks
Dike
Discordant tabular pluton
