geology exam 2

5 Main Mineral criteria

1) naturally occurring 2) inorganic 3) solid element or compound 4) definite chemical composition 5) regular internal crystal structure

during mountain building, as crustal thickness increases, some of the added thickness goes into depending the root, and some adds to the height of the mountain range. Approximately how much of an increase in crustal thickness is required to add 2 meters to the elevation of a mountain range?

10 meters

say we have a rock sample with 100 parent atoms and 1,500 daughter atoms, how many half lives have elapsed since it formed?

4

Minerals

A solid inorganic substance of natural occurrence.

ox bow lake

An arc-shaped lake which has been cut off from a meandering river

Basalt

Mafic (high iron, dark toned), volcanic (extrusive, aphanitic)

what are the top 3 elements in continental crust, by weight percentage

Oxygen (47%) silicon (28%) and Aluminum (8.1%)

recurrence interval for a flood of rank M is just the inverse of probability

T=1/P=(N+1)/M

alluvial fan

a fan-shaped mass of material deposited by a stream when the slope of the land decreases sharply

stream

a flowing water within a channel (includes rivers)

delta

a low triangular area where a river divides before entering a larger body of water

capacity

a measure of the total load of material a stream can move

hydrograph

a plot of discharge or stage over time

drainage basin

a region from which a stream draws water

stage

a rise in the water

longitudinal profile

a sketch of a stream's elevation from source to mouth

rock

a solid aggregate of one or more minerals, or mineral materials

unconformity

a time gap in the rock record, from non deposition of erosion

the evacuation of a city in advance of a hurricane is an example of

an adjustment

decompression melting

as rock moves up, towards the surface, it experiences a drop in pressure, this will cause the melting temperature of the minerals in the rock to decrease. Then can allow some of the minerals to melt

Effects of urbanization or development on flood plain

asphalt and concrete, buildings and land fill, storm drains, vegetation loss

gravel would normally be carried as what type of load by a stream

bed load

intrusive/plutonic rocks cooled slowly deep beneath Earth's surface

big to moderate sized visible crystals

floodplains

broad, fairly flat expanse of land covered with sediment around the stream channel. An area into which the stream spills over during floods

how does sedimentary rocks form

by weathering of pre-existing rocks minerals, lithification

erosion concentrated in valleys

can cause peaks to become higher

Common nonsilicate minerals

carbonates, sulfates, sulfides, oxides, native elements

suppose you are told that the area where you lived was once a shallow sea that evaporated. What kind of rock are you most likely to find hat is related to that time

chemical

sedimentary rocks

clastic sediment and clastic sedimentary rocks

caldera

collapsed magma chamber

volcanoes are

composed of different materials

gravel

conglomerate, ranges from rice grains to oranges

recurrence interval

curve is constructed by plotting discharge (or stage) as a function

pyroclastic flows

dense cloud formed from combination of tephra and volcanic gases

sedimentary rocks transportation process sorts grains so

deposits may have characteristic grain size (e.g., sand on a beach)

fossil succession

describes the predictability of fossil distribution through time. Fossils which are commonly preserved in sedimentary rocks are extremely useful as time markers for relative age dating. This is because specific fossils are only found within a limited, often narrow, time range

magma viscosity

escaping gases drive volcanic eruptions

mountains are areas of

extra crustal thickness

vegetation loss

farm lands and urban areas remove natural vegetation and expose the soil

rhyolite

felsic (low iron, light toned), volcanic (extrusive, aphanitic)

The Rise and Fall of Mountains

for every 1,000 meters of rock eroded from mountains, isostasy results in just 200 meters decrease in elevation

how does magma viscosity impact the type of volcanic eruption we should expect

gases are dissolved in magma, pressure on magma decreases as magma rises toward surface, gases are released

does does igneous rocks form

hot, molten rock material

reasons for floodplain occupation

ignorance of flood hazards, inexpensive land, nutrient rich soils

andesite

intermediate, volcanic (Extrusive, aphanitic)

why are mountains so long lived

isostasy (theory of floating) - deep root floats back up, partially replacing material lost to erosion

density of continental crust is about 80% of the density of mantle rock

it floats with 20% sticking up, and 80% forming the root

a 50 year flood occurs this year in a stream near where you live. How likely is it that a 50 year flood will occur next year

just as likely as it was this year

braided stream

localized sediments developed in the channel with obstacles and the localized sediments divide the channel into a complex system of many channels-sediment choked

limited by the available data

long term data sets are hard to come by, limited observations do not indicate what could happen, only what has been seen and recorded

lava flows

low viscosity lava, transported to front of lava flows in long lava tubes, build up in a series of layers

wet melting

melting caused by introducing water into a rock

rocks that are formed by the crystallization of new minerals in the solid state (without melting) due to high heat and/or pressure are

metamorphic

which plate tectonic setting produces partial melting that is due to rock experiencing a reduction in pressure (i.e., decompression)

mid-ocean ridge

uniformititarianism

most features we see are the product of slow, gradual processes, which we can observe today, acting over many millions of years. The present is the key to the past

lahars

mudflows formed when volcanic debris mixes with streams of melting ice

common silicate minerals

muscovite, Biotite, Quartz, Feldspar, Pyroxene, and Olivine

different sizes

note size of trees on volcano slope

isotopes

number of neutrons for an element may not be the same, variable numbers of neutrons possible

faunal succession

observation that assemblages of fossil plants and animals follow or succeed each other in time in a predictable manner, even when found in different places

flood

occurs when input exceeds output. Excess rain or snowmelt or temporary blockages are common causes

cross-cutting relationships

older rocks may be cut by younger rocks or features

where are the oldest rocks on the atlantic seafloor located

on the outer edges of the ocean basin

relative dating key principles

original horizontality, superposition, cross-cutting relationships, inclusions, faunal/fossil succession

The recurrence interval is the time interval we should expect

over the long term between events of a particular size

granite

plutonic (intrusive, phaneritic), felsic (low iron, light toned)

diorite

plutonic (intrusive, phaneritic), intermediate

gabbro

plutonic (intrusive, phaneritic), mafic (high iron, dark toned)

Peridotite

plutonic (intrusive, phaneritic), ultramafic

how does metamorphic rocks form

pre-existing rock or minerals heat, pressure, and chemically active fluids cause changes in rock without melting heat increases pressure increases fluids become heated and circulate

partial melting

produces more silica-rich melt (magma) relative to the rock being melted

relative dating

putting events in order

radiometric dating

radioactive isotopes decay over time, with a particular half life. Measuring the ratio of parent to daughter gives us the number of half lives elapsed

800 meters of change accommodated by

raising the crustal root

storm drains

rapid delivery of storm water to streams causing increase in storm height

asphalt and concrete

reduce infiltration

buildings and land fill

reduced water volume, raises stream height

streams can split up

reducing the ability to rapidly carry water away

sedimentary rocks rock names

reflect grain size

tephra

represents particles blasted into air by eruption, volcanic bombs and ash are found near and far from eruption source

the lettered groups in the figure below show the arrival times of the three main types of seismic waves. Group K represents the second set of waves to arrive at each station. What type of wave does group K correspond to?

s, or shear

sand

sandstone, ranges from sugar to coarse salt

point bar

sediment deposited on the insides of meanders

original horizontality

sedimentary rocks are deposited in nearly horizontal layers

3 main types of rock

sedimentary, metamorphic, igneous

clay

shale, mudstone, smaller than granulated sugar

3 main types of volcanoes

shield, stratovolcano, and cinder cone

how does silica affect magma viscosity

silica is a combination of oxygen and silicon that combines with other elements to form minerals (less silica=low viscosity) (more silica=high viscosity)

silt

siltstone, smaller than granulated sugar

meander

streams don't flow in straight lines and erode old banks and create new banks, and thus bends form in the streams, curves in a stream (or river)

elements

substance composed of atoms with the same number of protons

eruption products

tephra, gases, lava flows, pyroclastic flows, lahars

flood plain

the flat, wide area of land along a river

base level

the lowest elevation to which the stream can erode downward (often lake or sea level elev)

cut bank

the outside and downstream side of the meander, faster water flows

the focus of an earthquake is

the point on the fault surface where seismic energy is first released

if you go out equal distances on either side of a mid-ocean ridge and measure the magnetic polarity, those polarities will be

the same

gradient

the steepness of the stream channel

load

the total quantity of material that a stream transports by all methods (traction, saltation, suspended, and dissolved)

discharge

the volume of water flowing past a given point/cross section in a specified length of time

why are mountains there

thicker crust

Extrusive/volcanic rocks cool quickly at or near Earth's surface

tiny to invisible crystals

flood frequency/flood-recurrence curve

tool to evaluate frequency of flood events

purely statistical

treats floods as purely random events, doesn't capture any understanding of, or change in, cases for flooding

complex impact craters have a central peak unlike simple craters

true

eclogite

ultramafic, volcanic (extrusive, aphanitic)

superposition

undeformed sequence (Stack) of rocks, the younger rocks overlie the older rocks

evenly distributed erosion causes

uniform lowering of mountains

volcano type and eruption style

varies with plate setting

how does temperature content affect magma viscosity

viscosity of materials decreases with increasing temperature

gases

water vapor, sulfur dioxide, carbon dioxide, may affect climate patterns

what type of melting does subduction produce?

wet

two types of melting

wet and decompression

the big island of hawaii is the present day position of a hot spot. Compared to the islands to the northwest, such as Maui, Molokai, Oahu, the big island of Hawaii is

younger

inclusions

younger rocks may incorporate pieces of older rocks