Mastering Geology

What is an accessory mineral?

A mineral that makes up a relatively small portion of the total rock composition

What is meant by the statement "Every metamorphic rock has a parent rock"?

All metamorphic rocks are created only through the change of preexisting rock.

In general, when will melted rock in the mantle rise?

Almost always

Precipitation in the case of sedimentary rocks means that a solid rock forms how?

As crystals in a liquid

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

Differentiate between the formation of biochemical rocks and the formation of inorganic chemical rocks.

Biochemical rocks form from organisms that were once alive, such as limestone from marine shells, whereas inorganic chemical rocks form from nonbiological processes, such as salt that is left behind when a lake evaporates.

How is igneous rock formed?

By crystallization of magma

Describe the three types of common cements in sedimentary rocks?

Calcite (which effervesces in dilute acid), silica (which produces the hardest sedimentary rocks), and iron (which gives rocks a reddish color)

What are the four agents that drive metamorphism?

Directional stress, pressure, heat, and chemically active fluids

Which processes result in mineral flattening during metamorphism?

Dissolution followed by crystallization

What is a necessary condition involved in the creating of metamorphic rock?

Elevated temperatures and/or pressures

When rocks experience high temperatures and differential stresses deep in Earth, their grains tend to do what?

Flatten and elongate

What are the four basic compositional groups of igneous rocks, ranging from the highest silica content to the lowest silica content?

Granitic, andesitic, basaltic, and ultramafic

What mineral is the major component of rock salt?

Halite

What is the primary agent of contact metamorphism?

Heat

How are felsic magmas formed?

Heat from the mantle melts part of the lower crust.

What is the single-most common and characteristic feature of sedimentary rocks?

Horizontal strata or beds

What is an important condition for the formation of coal

Incomplete decomposition of organic matter due to a lack of oxygen

What is the most abundant chemical sedimentary rock

Limestone

What is the common rock produced by the metamorphism of limestone?

Marble

High heat and high pressure (without melting) will lead to what type of rocks?

Metamorphic

Why do bands of minerals form when rocks are put under normal stress?

Minerals dissolve, atoms migrate to new locations, and minerals reform.

What three things does metamorphism change within a rock?

Metamorphism can change the mineralogy, texture, or chemical composition of a rock.

What are three examples of fossil fuels?

Oil, coal, and natural gas

How will minerals orient when a rock is put under shear stress?

Parallel to the direction of the shear stress

What texture describes an igneous rock with anomalously large crystals?

Pegmatitic

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

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 are the two most common minerals in detrital rocks?

Quartz and feldspar

When sand lithifies, the resulting rock is commonly called what?

Sandstone

Igneous rocks are classified on the basis of what two main characteristics?

Texture and mineral composition

Recrystallization during metamorphism causes grains to grow longer in what?

The direction perpendicular to the compressional stress

Chemical sedimentary rocks form from what?

The precipitation of minerals from dissolved substances

What factors influence the texture of an igneous rock?

The rate at which the rock cools, the amount of silica that is present in the magma from which it forms, and the amount of dissolved gases present in the magma

What does a porphyritic texture indicate about the cooling history of an igneous rock?

The rock began cooling under the Earth's surface, but then was moved to above the Earth's surface where it finished cooling.

What does an igneous rock with a pyroclastic texture tell a geologist?

The rock was likely formed by a violent volcanic eruption.

What is rock texture?

The way a rock looks

How do evaporites form and what are two common examples?

They form when minerals that were previously dissolved in water are deposited as the water evaporates; rock gypsum and rock salt

Why are silts and clays commonly deposited in lakes, lagoons, swamps and marine environments?

Those settings have relatively still water

How do metamorphic rocks reach Earth's surface?

Through removal of overlying rocks

Chemical weathering would be most effective in what type of climate?

Warm and humid

What is Confining pressure?

When forces are applied equally in all directions

Can one magma produce several different types of igneous rocks with different mineral compositions?

Yes