SCI 2010 Chapter 20
When will magma rise to Earth's surface? when the magma is denser than adjacent rock when the magma is less dense than adjacent rock when the magma has more volume than adjacent rock When the magma has more mass than adjacent rock.
when the magma is less dense than adjacent rock
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 the magma types in order of increasing (low to high) silica content: (a) basaltic, (b) granitic, (c) andesitic.
ACB
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, from first to last, the episodes that brought about Earth's uneven distribution of elements:
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.
In general, why does Earth's crust sit on top of the mantle?
Earth's crust is less dense than the mantle.
How are felsic magmas formed? Pressure from overlying crust forces mantle magmas through cracks to Earth's surface. Heat from the mantle melts part of the lower crust. Felsic magmas form when volcanoes mix mafic rock with dissolved gases. Felsic magmas generally do not exist.
Heat from the mantle melts part of the lower crust.
Why do bands of minerals form when rocks are put under normal stress?
Minerals dissolve, atoms migrate to new locations, and minerals reform.
Could metamorphic rocks reach the surface of a planet without rock-uplifting processes?
No, metamorphic rocks must be uplifted and exposed by erosion.
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.
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.
What lies underneath volcanic features at Earth's surface?
What is the difference between a dike and a sill? A sill intrudes across sedimentary layers, and a dike intrudes between sedimentary layers. A dike intrudes across sedimentary layers, and a sill intrudes between sedimentary layers. A dike leads to volcanoes above sedimentary layers, and a sill leads to volcanoes below sedimentary layers. A sill leads to volcanoes above sedimentary layers, and a dike leads to volcanoes below sedimentary layers.
In general, when will melted rock in the mantle rise? sometimes, depending on the magma's temperature almost always almost never sometimes, depending on the magma's pressure
almost always
What is foliation?
banding in metamorphic rocks that results from the reorientation of minerals
What is a magma chamber called after the conduit has solidified and been exposed by erosion?
batholith
Where do most metamorphic rocks form?
between a few and many kilometers beneath Earth's surface
Which processes result in mineral flattening during metamorphism?
dissolution followed by crystallization
What would you call a granite that has undergone metamorphism and now exhibits foliation?
gneiss
Young Earth developed a layered structure under the influence of
gravity and density segregation-the process of differentiation.
The three sources that brought young Earth to its melting point were
impact heating, gravitational contraction heating, radioactive decay heating.
Minerals are composed of
inorganic solids.
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
How will minerals orient when a rock is put under shear stress?
parallel to the direction of the shear stress
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
The two most abundant elements in Earth's crust are
silicon and oxygen.
Based on its abundance in Earth's crust, most rocks contain a mineral composed of the elements oxygen and
silicon.
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
