how do minerals form? notes: 3/13/09. how do mineral crystals form? a. rivers carrying sediment...
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How do minerals form?
Notes: 3/13/09
How do mineral crystals form?
A. Rivers carrying sediment deposits it somewhere
B. Water evaporates leaving behind minerals that were dissolved
C. Molten rock cools and crystallizes.
D. All of the above
E. B and C only
Crystallization of Melted Minerals
The closer to the surface, the faster the magma cools Slow cooling (1000s of years) Fast cooling (The minerals get hard before the
atoms have time to get into crystal shapes)
Crystallization of Minerals Dissolved in Water
Hot water solutions in the earth cool and minerals form Example: metals found
in veins Evaporating water can
leave behind crystals Example: sea water
leaving potassium crystals
Types of Minerals
Silicates Contain a mixture of
oxygen and silicon make up 75-90% of
earth’s crust
Nonsilicates NOT formed from
oxygen and silicon Combinations of
oxygen, iron, carbon, and sulfur
3.2 Igneous Rocks3.2 Igneous Rocks
As molten rock cools, minerals crystallize and form igneous rocks.
Extrusive igneous rocks cool quickly at Earth's surface.
Intrusive igneous rocks cool slowly within Earth.
What type of igneous rock has larger mineral crystals?
A. Intrusive, because it cools more slowly
B. Extrusive, because it cools more quickly
C. Volcanic, because of the gas present
D. Sediment, because there’s more layers
Intrusive Extrusive Cools in the earth more
slowly
Larger Mineral Crystals Examples: granite and
gabbro When surface rock wears
away, intrusive rock can surface; it is harder and
lasts longer
Cools on earth’s surface quickly
Small mineral crystals or none at all
Examples: scoria, pumice, obsidian
Low silica = flows easy; volcanoes with gently sloping sides (Hawaiian islands)
High silica = cone shaped volcanoes with steep sides
The color igneous rocks is determined by how much silica is in it.
A. Yes
B. No
Composition of Igneous Rocks
Most are made of silicates High in silicates = light color Low levels of silicates = dark color
As a rock gets buried deeper in the earth, which of the following does NOT happen?
A. It can get melted into magma.
B. It can turn into sediment.
C. It can start the process of foliation.
D. More mica can start to form.
Why do rocks change as they get buried deeper? Increased heat Increased pressure
heat and pressure
3.43.4 Metamorphic rocks form as existing rocks change.
Metamorphic rocks form as the structure of the parent rocks change and as their minerals recrystallize.
shale schist
recrystallization
foliation
The process by which bonds between atoms in minerals break and re-form in new ways during metamorphism.
The arrangement of minerals within rocks into flat or wavy parallel bands; a characteristic of most metamorphic rocks.
What is the third type of rock called?
Main PROCESS that makes sedimentary rock…
“WETDC” Weathering Erosion Transportation Deposition Cementation
SEDIMENTARY
What is true about limestone?
A. It is made from water evaporating.
B. It is made from shells.
C. It only forms in the desert.
3.33.3 Sedimentary rocks form from earlier rocks.
sedimentLayers of sedimentary rocks form as
• sediments are pressed or cemented together
• dissolved minerals re-form as water evaporates
Limestone: forms when shells are cemented together and some of the minerals dissolve and reform. (reacts with acid because of the calcite)
Fossils: are found only insedimentary rocks
Where would a conglomorate sedimentary rock most likely be formed?
A. Where a river is moving rapidly.
B. Where a river is moving slowly.
C. In the ocean.
Different types of sedimentary rocks form because of the speed of the water.
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