PS chapter 20 HW pt 1
What is the mass of a 4-galgal pail of gold?
277.92 kg
What is the difference between a dike and a sill?
A dike intrudes across sedimentary layers, and a sill intrudes between sedimentary layers
What is a mineral?
A mineral is a naturally formed, inorganic, crystalline solid with an ordered arrangement of atoms and a specific chemical composition.
What is a polymorph?
A polymorph is two minerals made from the same combination of elements but with different crystal form.
From hardest to softest, rank the following minerals: (a) corundum, (b) feldspar, (c) fluorite, (d) gypsum.
ABCD
Rank these rock-forming minerals from most abundant to least abundant: (a) silicates, (b) carbonates, (c) sulfates, (d) oxides.
ABCD
Rank these minerals in order of partial melting: (a) quartz, (b) feldspar, (c) olivine, (d) pyroxene.
ABDC
Rank the magma types in order of increasing (low to high) silica content: (a) basaltic, (b) granitic, (c) andesitic.
ACB
Describe the process of crystallization.
Atoms from a gas or liquid bond together in a solid geometric array.
Name the rock for each statement, then rank them from low to high grade:
BCA
Rank the following properties used for mineral identification from most useful to least useful: (a) color, (b) hardness, (c) streak, (d) cleavage
BDCA
What do freeze-thaw and salt weathering have in common?
Both freeze-thaw and salt weathering require rain and force rocks apart physically.
Rank the following stages of sedimentary rock formation from first to last: (a) erosion, (b) lithification, (c) weathering, (d) deposition.
CADB
Most mineral samples do not display their crystal forms. Why not?
Crystal growth is limited by space constraints.
Rank, from first to last, the episodes that brought about Earth's uneven distribution of elements: (a) gravitational attraction, (b) radioactive decay heating, (c) density segregation, (d) impact heating.
DABC
Why are mineral bands in metamorphic rocks light and dark colored?
Dark minerals rich in iron and magnesium separate from light minerals rich in silica and aluminum.
Why is oxygen the most common element in Earth's crust, but not in Earth as a whole?
Density segregation - dense elements sank to Earth's center, and lighter elements rose to the surface.
In general, why does Earth's crust sit on top of the mantle?
Earth's crust is less dense than the mantle.
Silicate minerals are subdivided into ferromagnesian silicates and nonferromagnesian silicates. What two factors contribute to this subdivision?
Ferromagnesian silicates contain iron and/or magnesium.
Distinguish between foliated and nonfoliated metamorphic rocks.
Foliated metamorphic rocks have layers made by parallel flakes or sheets of minerals. Non-foliated rocks have random arrangements of mineral crystals.
What are the most common igneous rocks and where are they generally found ?
Granite found on continents; basalt found on the sea floor
How are felsic magmas formed?
Heat from the mantle melts part of the lower crust.
What is the primary determining factor for a rock's melting/crystallization point?
High silica content rocks have the lowest melting point.
Name the three major types of rocks and describe the conditions of their origins.
Igneous: rock cooled from a molten liquid Sedimentary: rock formed from sediments glued together or from evaporites Metamorphic: rocks transformed by heat and/or pressure without melting
What is partial melting?
Magma made from only the fraction of minerals that have melted.
What is metamorphism? What causes it?
Metamorphism is the recrystallization of minerals or mechanical deformation. It is caused by the change in temperature and/or pressure.
Why do bands of minerals form when rocks are put under normal stress?
Minerals dissolve, atoms migrate to new locations, and minerals reform.
How did density segregation contribute to Earth's internal layers?
Molten material settled under gravity to produce dense core, less dense mantle, and least dense crust.
Could metamorphic rocks reach the surface of a planet without rock-uplifting processes?
No, metamorphic rocks must be uplifted and exposed by erosion.
With respect to the silica content of the parent rock, what type of magma does partial melting produce?
Partial melting produces magma enriched in silica..
How are metamorphic rocks formed?
Preexisting rock is altered through heat and pressure.
How do mafic volcanic rocks get to Earth's surface?
Pressure from overlying crust forces mantle magmas through cracks to Earth's surface. These magmas erupt out of volcanoes, cool, and solidify into rock.
What is a clastic sedimentary rock?
Sedimentary rocks made from small pieces
What is the difference between a silicate mineral and a nonsilicate mineral?
Silicate minerals contain silicon and oxygen; nonsilicate minerals do not contain them.
As minerals crystallize in cooling magma, are the minerals with lower amounts of silica or the minerals with higher amounts of silica the first to crystallize?
The minerals with the lower amounts of silica crystallize first.
Why are volcanic rocks often exposed at Earth's surface as hills, ridges, and mountains surrounded by areas of lower elevation?
Volcanic rocks are often more resistant to erosion than surrounding rock.
Why does water frozen in the cracks of a rock help to break down the rock?
Water expands when frozen and physically forces the rock apart.
How does weathering produce sediment? Distinguish between weathering and erosion.
Weathering breaks up a rock mechanically or by chemical reactions. Weathering occurs in place; erosion moves the weathered particles.
Minerals are made up of different elements, and rocks are _______.
a physical mixture of materials - minerals, fossils, fossil fragments, and/or organic matter
Rocks can begin to melt if
all of the above
In general, when will melted rock in the mantle rise?
almost always
What is foliation?
banding in metamorphic rocks that results from the reorientation of minerals
Where do most metamorphic rocks form?
between a few and many kilometers beneath Earth's surface
How are most carbonate rocks formed?
biological activity
In an area of regional metamorphism, if buried rock begins to melt it _______.
can become igneous rock
Before beach sand becomes rock it must be _______.
compacted, cemented, and lithified
A mineral's physical properties are dependent on _______.
composition, structure, and bonding
What are the three most common clastic sedimentary rocks?
conglomerate, sandstone, and shale
Which processes result in mineral flattening during metamorphism?
dissolution followed by crystallization
When water evaporates from a body of water, what type of sediment is left behind?
evaporite sediment
What would you call a granite that has undergone metamorphism and now exhibits foliation?
gneiss
What physical properties are used to identify minerals?
hardness, cleavage, color, and density
Rocks formed by cooling from a molten state are
igneous rocks
hat three sources of heat contributed to the melting and density segregation of early Earth?
impact heating, gravitational contraction, and radioactive decay
In Earth's interior, does temperature increase or decrease with depth?
increases
What is the most abundant element for Earth as a whole?
iron
What is the most abundant carbonate rock?
limestone
As magma cools, the first minerals to crystallize are those with a _______.
low silica content
What does inorganic mean in the definition of a mineral?
made from materials that are not part of a living thing
What are two sources from which minerals crystallize?
magma and water solutions
What lies underneath volcanic features at Earth's surface?
magma chambers and volcanic conduits
Which two rock types would you expect to see sitting next to each other after a very long period characterized by only uplift and erosion?
metamorphic and sedimentary rocks
If a rock contains mineral A (30% silica) and mineral B (25% silica), which would melt last as temperature increases?
mineral B
In the process of crystallization, the remaining magma becomes _______.
more and more silica enriched
In contact metamorphism, water-rich, low-melting temperature minerals are found far away from the contact zone. Give two examples of such minerals.
muscovite and chlorite
Silicates are the most common rock-forming minerals because _______.
oxygen and silicon are the two most abundant elements
What is the most abundant element in Earth's crust? What is the second most abundant element?
oxygen; silicon
What is the most abundant mineral in Earth's crust? What is the second most abundant mineral?
oxygen; silicon
How will minerals orient when a rock is put under shear stress?
parallel to the direction of the shear stress
The great variety of igneous rocks is due to _______.
partial melting and the step-by-step process of crystallization
How will foliation in continental metamorphic rocks formed during subduction be oriented?
perpendicular to the direction of plate movement
How will minerals grow when a rock is put under normal stress?
perpendicular to the direction of the greatest stress
How will minerals orient when a rock is put under normal stress?
perpendicular to the direction of the greatest stress
Do metamorphic rocks look like the preexisting rock from which they form?
sometimes, but not always
What is salt weathering?
the formation of minerals in rock cracks during the evaporation of salty water, forcing rock apart
What is rock texture?
the way a rock looks
How do metamorphic rocks reach Earth's surface?
through removal of overlying rocks
What is a volcanic conduit called after the conduit has solidified and been exposed by erosion?
volcanic neck
When will magma rise to Earth's surface?
when the magma is less dense than adjacent rock