Geology

scoria

a glassy, mafic, igneous rock containing abundant air-filled holes

Contours form closed loops around_________Contours form closed loops around_________

depressions hills

arkose sandstone

- rich in orthoclase feldspar - clastic - good sorting - angular - alluvial fan or floodplain

To show topography in a rugged, mountainous area, the most appropriate contour interval would be

100 ft

To show topography in a flat coastal area, the most appropriate contour interval would be

5 ft

Peridotite

A coarse-grained ultramafic rock.

Basalt

A dark, dense, igneous rock with a fine texture, found in oceanic crust

Rhyolite

A light-brown to gray, fine-grained extrusive igneous rock with a felsic composition. The extrusive equivalent of granite.

Gabbro

A mafic, coarse-grained igneous rock composed predominantly of ferromagnesian minerals and with lesser amounts of calcium-rich plagioclase feldspar.

lithic sandstone

A sandstone containing many particles derived from fine-grained rocks, mostly shales, volcanic rocks, and fine-grained metamorphic rocks

Plagioclase Feldspar

Harder than Glass Vitreous 90 degrees two directions may be iridescent

What does a map scale of 1:24,000 indicate?

One inch on the map equals 24,000 inches on the ground. One centimeter on the map equals 24,000 centimeters on the ground. One foot on the map equals 24,000 feet on the ground.

What changes take place during physical weathering?

Rocks are broken into smaller pieces.

What changes take place during chemical weathering?

The mineralogy of previously existing rocks changes.

What does Bowen's reaction series describe?

The order of crystallization of minerals from the melt as it is cooling

A benchmark is

a permanent marker on the ground that indicates location and elevation.

Augite (pryroxene family)

about the same as glass, cleavage in 87 and 90 degrees, commonly elongated crystals

sedimentary rocks are unique in that they form

by processes that operate at or near the Earth's surface.

Geologists classify minerals into groups like silicates by their

chemical composition

Biogenic sedimentary rocks are similar to ______________ in that ______________.

chemical sedimentary rocks; removal of dissolved ions from water is an important process in their formation

wacke

clastic sedimentary rock- sand and rock fragments in a muddy matrix

Which of the following physical properties of a mineral depends on the strength of the bonds that hold its atoms and ions together?

cleavage

amphibole family (hornblende or actinolite)

cleavage in 56 and 124 degrees, commonly elongate or needle like crystals

What is the result when chemical bonds in a mineral are stronger in some directions than in others?

clevage

A fine-grained texture most likely formed when a magma cooled

close to the earths surface

Galena

color: silvery or gray, streak gray, softer than glass harder than a penny, three clevage directions at 90 degrees

limestone

composed of calcite,

When the chemical bonds in a mineral are equal in all directions, what will the result be?

conchodial fracture

olivine

conchoidal fracture, green, may occur in granular masses

Garnet

conchoidal fracture, often a 12 sided crystal

__________________ occurs at ocean ridges, whereas __________________ occurs at subduction zones.

decompression melting; flux melting

Small tick marks (hachures) on contour lines indicate

depressions.

Mohs hardness scale describes the relative hardness of ten minerals, not their absolute hardness. This means that

diamond will scratch talc, but talc won't scratch diamond

Solidified lava flows and volcanic ash deposits are examples of

extrusive igneous rocks

Obsidian

felsic/ intermediate, glassy

Siltstone

fine size, silt clast size, silt sized clasts

pyrite

gold, brassy yellow, harder than a penny

Which property of a protolith may change during metamorphism?

grain size, shape and mineralogy

Hematite

harder than a penny softer than glass, usually too fine grained, earthy luster reddish brown

calcite

harder than a penny, cleavage in 3 directions not 90 degrees, reacts with HCL

Quartz

harder than glass, conchoidal fracture, often elongated 6 sided crystals

potassium feldspar

harder than glass, two direction 90, no striations

Glassy igneous rocks

have no minerals

granite

high silicate, coarse grained, felsic

granitic pegmatite

high silicate, pegmatic

Diorite

intermediate, phaneritic

breccia

medium to coarse, angular pebbles

muscovite

non-metallic, softer than a finger nail, clevage in one direction, splits into thin transparent sheets

Which of the following physical properties will change when you break a mineral into smaller pieces?

none of these properties (hardness, specific gravity, and clevage) will change despite how small the specimen becomes

Well-rounded grains in a clastic sedimentary rock indicate

numerous collisions between particles during extensive transportation.

) Contour lines on a map connect points

of equal elevation.

Pumice

porous, felsic and intermediate

Porphyritic andesite

porphyritic, intermediate

coal

primarily composed of carbon, plant material, buried and underwent diagenesis

Angular grains in a clastic sedimentary rock indicate

rapid, typically short-distance transport.

The grain size of an igneous rock is determined by the

rate of cooling, which controls the amount of time ions have to migrate to crystal seeds.

Conglomerate

rounded pebbles, blouder, coarse to very coarse

The zero contour line is also known as

sea level

What does the assemblage of minerals in a metamorphic rock help to determine?

the chemical composition of a protolith the temperature at which metamorphism took place the pressure at which metamorphism took place

What does the term metamorphic grade refer to?

the degree to which a metamorphic rock's protolith has changed

The absence of preferred orientation of minerals in a metamorphic rock may be due to which of the following?

the lack of stress during metamorphism the absence of platy minerals like mica the absence of rod-shaped minerals like amphibole

Foliation and lineation are terms that describe

the orientation of minerals in metamorphic rocks.

Metamorphic index minerals help geologists determine

the temperature and pressure conditions during metamorphism.

Information on the borders of a topographic map includes all except

the types of rocks present in the map area.

A vertical exaggeration of 1.00 × on a topographic profile means

the vertical scale of the profile is the same as the map scale.

Polymorphs (minerals like diamond and graphite that have the same chemical composition but are nevertheless different minerals) exist because

their mineral structures differ based on the different temperature and pressure conditions under which they form

The agents that cause metamorphism include all except which of the following?

time

A porphyritic texture indicates that an igneous rock had

two different cooling rates

Shale if breaks into platy sheets

very fine, clay, clay and or very fine silt

A mature clastic sedimentary rock is characterized by what properties?

well-rounded grains, good sorting, and minerals resistant to chemical weathering

Which of the following describes the formation of chemical sedimentary rocks?

Their minerals form by precipitation of ions from water. Their minerals form from ions dissolved from previously existing minerals during chemical weathering. Their minerals form with a crystalline texture.

Chert

a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils.

Which of the following might clastic sedimentary rocks contain?

individual mineral grains separated from previously existing rocks during weathering rock fragments made up of several minerals fragments of volcanic glass

Quartz is not a good index mineral because

it is stable over a very wide range of temperatures and pressures.

Marble is metamorphic rock that was originally _______.

limestone

the presence of water

lowers the melting temperature during flux melting. helps the magma rise toward the surface. causes explosive volcanic eruptions.

Formation of large grains in an igneous rock is aided by

magma with a low viscosity very slow cooling the presence of water in the magma

Magnetite

magnetic, color black or dark gray, streak black and harder than a glass plate

Every mineral has a preferred habit (crystal shape), but most mineral grains do not display that shape because

many grains interfere with one another while they are growing

Coquina

mass of shells poorly cemented together, minimal diagenisis

Sandstone

medium size, sand grains, quartz grains

Diamicite

medium to coarse, pebbles boulder, muddy matrix

Which mineral is responsible for the strong foliation in a schist?

mica

Most fossils are found in sedimentary rocks because

sedimentary rocks form in the same environment where the plants and animals lived and died.

Talc

softer than a finger nail, cleavage in one direction, nonmetallic, feels greasy

kaolinite

softer than a fingernail, cleavage rarely seen, typically powdery mass, sticks to tongue

Halite

softer than a penny, cleavage 3 directions 90 degrees, cube shaped crystal, tastes salty

biotite

softer than a penny, splits into thin sheets, elastic cleavage sheets; transparent

what is a mineral

solid crystalline definite chemical composition

gypsum

splits into slabs, fine grained, granular

Graphite

streak gray-black, softer than a finer nail, one cleavage direction, platy appearance

Where are intermediate igneous rocks (andesite and diorite) most commonly found?

subduction zones

Which of the following mineral properties is chemical rather than physical?

taste