Geography 201 - Exam 2

Secret word of the day Feb 2

rocks

Elements combine to form

minerals

minerals

inorganic, natural compounds with a specific chemical formula and crystal structure

One or more minerals combine to form

rocks

Physical and chemical properties of rocks are dictated by

how and where they form

mineralogy

 the study of minerals, including their molecular structure and crystalline properties 

Common properties of Crystals

1. Color
2. Streak
3. Luster
4. Crystal Form
5. Cleavage and Fracture
6. Hardness
7. Specific gravity 
8. Others

presence of certain minerals effects the rocks

color

Green beryl is

emerald

blue corundum is

sapphire

red corundum is

ruby

Streak

color of powdered rock left on another surface when scratched

Some minerals have a distinct _____ that is different from their____

streak color , surface or crystal color

Luster

the manner in which a mineral shines or reflects light

Luster example

molybdenite with bright metallic luster

Crystal Form

the shape of a crystal, including the number of crystal faces and the angles between them

cleavage planes

Planes of weakness along which crystals break are determined by their molecular structure

do all crystals have cleavage planes

no, not all crystals have cleavage planes

hardness

ability to scratch mineral surfaces

Mohs hardness scale for

hardness of common minerals

Specific gravity

the ratio between the mass of the mineral and the mass of an equal volume of water

Petrology

the study of rocks and the conditions under which they form

Rock cycle

the transitions among the three main rock types through geologic time

Three main types of rocks are

igneous, sedimentary, metamorphic

Igneous rocks

formed from the coding of molten magma (liquid rock)

molten magma is

liquid rock

two primary types of igneous rock

extrusive (volcanic) and intrusive (plutonic)

Extrusive (volcanic)

form when magma reaches the Earth’s surface and cools quickly

Intrusive (plutonic)

form when magma crystallizes and solidifies underground

extrusive rocks are

usually fine grained (small crystals) because lava cools too quickly for crystals to grow

example of an extrusive rock

basalt

intrusive rocks are

typically coarse-grained (large crystals) because crystals grow as rock cools more slowly

intrusive rocks have ____ crystals

large

extrusive rocks have ___ crystals

small

Example of intrusive rock

Granitics in Yosemite, California

Felsic

relatively rich in elements that form feldspar and solicit minerals (silicon, oxygen, aluminum); usually light in color and lower density

are felsic rocks dense

no, they are lower in density

what color are felsic rocks

a light color

Mafic

relatively rich in magnesium and ferric (iron based) minerals; darker in color, more dense and containing less silicon dioxide

mafic rocks are often ____ in color

darker

mafic rocks are ___ based

iron

mafic rocks are rich in

magnesium and ferric (iron based) minerals

are mafic rocks dense

yes, mafic rocks are dense

clastic rocks are formed by

granular sediments

Sedimentary Rocks

formed by the deposition and cementation of mineral, organic or chemical particles

granular sediments are

different pieces of soils or rocks

step 1 of forming clastic rocks

Weathering and erosion of existing rock

step 2 of forming clastic rocks

Transportation by wind, water, ice, and gravity

step 3 of forming clastic rocks

Deposition of material

step 4 of forming clastic rocks

Compaction and cementation by chemicals precipitated out of surrounding water

Clastic sedimentary rock examples

Shale: clay sized

Sandstone: sand-sized

Conglomerate: rounded pebbles or cobbles

Breccia: angular pebbles or block

Shale

clay sized

Sandstone

sand-sized

Conglomerate

rounded pebbles or cobbles

Breccia

angular pebbles or block

Chemical and organic sedimentary rocks are formed by

evaporates, chemical precipitates, or organic fragments 

Limestone

a sedimentary rock composed of the minerals calcite and aragonite, both forms of calcium carbonate

The most common sources of the calcium carbonate in limestone are

 shells from marine organisms. After they die, the shells settle out of the water and are deposited on ocean floors. 

metamorphic rocks are formed from

existing rocks are altered by heat, pressure, or chemical changes

Common rock conversions to metamorphic

1. Sandstone to Quartzite 
2. Granite to Gneiss
3. Limestone to Marble

Sandstone to

Quartzite

Granite to

Gneiss

Limestone to

marble

Causes of metamorphism

1. Pressure: burial or tectonic pressure
2. Heat: partial melting
3. Chemical changes: result of reactions

Pressure

burial or tectonic pressure

Heat

partial melting

Chemical changes

result of reactions

Foliation

planar or non random alignment of fabric in rock; alignment of crystals 

Schistosity

shiny surfaces on metamorphic rock due to alignment of small platy minerals

slate lacks

schistosity

Phyllite

has sheen due to alignment of microcrystals of mica 

The most common sedimentary rocks are

shale, sandstone, and limestone

Volano definition

a mountain or hill having a crater or vent through which lava, rock fragments, hot vapor, and gas are being or have been erupted from the earth’s crust

Magma chamber definition

a large underground pool of molten rock (magma) lying under the surface of the earth's crust 

Given enough time and pressure, magma and trapped gasses can

gradually fracture surrounding rock, creating outlets (vents) for the magma 

outlets are

vents for magma

crater definition

a bowl or funnel-shaped depression above the vent from which volcanic material is ejected

what is a volcano built from

layers of lava, ash, and dust from previous eruptions. 

Active

currently erupting or has done so in recent past 

Dormant

has not recently erupted but could still do so 

Extinct

has not recently erupted and is unlikely to do so

what are the three types of activity in volcanoes

active, dormant, extinct

Effusive eruption

an eruptive dominated by an outpouring of relatively fluid lava

viscosity

A liquid's resistance to flowing

Explosive eruption

a violent, eruption driven by gas accumulating under great pressure 

pyroclastic flows

 fast-moving currents of hot gas and volcanic matter

outer core composition

liquid iron and nickel

Outer core density

10\.7 g/cm3

Shield Volcano

a wide volcano with shallowly sloping sides formed by numerous low-viscosity lava flows; associated with effusive flows

what are shield volcanos associated with

effusive flows

Composite Volcanoes

steep sides interlayered with flows and pyroclastics shaped by explosive eruptions

caldera

a large volcanic crater formed by an explosive volcanic eruption and collapse of the cone

what forms a caldera

felsic magmas lead to explosive eruptions that lead to these forming

Lithosphere

outermost rigid zone

Asthenosphere

plastic zone in the upper mantle

Mesosphere

deep mantle of dense rock

Lava domes

lava fills the central vent, solidifies, and plugs the vent; pressures build to explosive levels

cinder cone definition

runny magma mixed with water beneath the ground. As this slurry reaches the surface, the water flashes into steam, causing the liquid rock to explode from the ground. These tiny bits of lava cool as they fall to the earth, forming tiny rocks called cinders and lapilli that pile up around the volcano's vent.

cinder cone has what kind of magma

runny

runny magma is mixed with what beneath the ground in a cinder cone

water