Understanding Earth EXAM 2

UNI, Dr. Iqbal

Meta

change

Morph

form

Ways that metamorphic rock can change

chemical composition and texture

Parent rock

the rock that gives rise to metamorphic rock/ preexisting rock

What type of rock can the parent rock be?

igneous, sedimentary, or metamorphic

Metamorphic rocks stay in what phase of matter the WHOLE time?

solid (solid to solid transformation)

Driving forces for metamorphic rock formation

heat, pressure, and chemically active fluid (water)

What is the Sun’s life expectancy?

9 billion years

Sources of heat as a driving force

heat trapped during formation of the solar system, plate boundaries

Geothermal gradient

30 degrees C/km, the Earth heats up the farther down you go

Is the geothermal gradient accurate all the way to the core?

no, only works for the crust and upper mantle

Confining pressure

pressure is on all sides of the rock

Directed pressure

pressure from one direction

Granular

rounded particles

What is a chemically active fluid?

water that has absorbed minerals from magma

Low grade metamorphic rock

evidence of parent rock is still present

High grade metamorphic rock

no traces of parent rock

Types of metamorphism

regional meta, contact meta, cataclastic meta, seafloor meta, burial meta

Regional meta

directed pressure is dominant, at convergence plate boundaries occurs at moderate to deep levels under moderate to ultra high pressure/temperatures

Contact meta

heat is predominant, rocks in contact with heat undergo metamorphosis

Metamorphose

being changed into a metamorphic rock

Cataclastic meta

found near plate boundaries where there is grinding and pressure

Seafloor meta

chemically active fluid is predominant, occurs at mid ocean ridges, where intruding magma drives seawater circulation through extruded basalts

Burial meta

confining pressure, rocks are below could and transforms sedimentary rocks by prograssively increasing temperature and pressure

Shock meta

results from heat and shock waves of meteorite impacts, transformed rock at impact site

In what conditions will a metamorphic rock not form?

low pressure low temperature environments

Where would you go to find the most metamorphic rock?

mountain tops

Types of foliation

foliated and nonfoliated

Foliated metamorphic rocks

flaky rock with particles going in straight lines, weaker than nonfoliated rocks

Nonfoliated metamorphic rocks

rocks with particles going in every direction

Foliation

angular or vertical layers of rock, different than bedding because foliation will go through bedding and bedding is horizontal

What metamorphic rock is formed from shale (going from low to high pressure)?

slate or phyllite → schist → Gneiss

Slate

thin foliation, minerals not visible

Phyllite

thin foliation, mineral not visible, glossy

Schist

thick foliation, minerals are visible

Gneiss

thick and wavy foliation, minerals are visible, light and dark minerals are separate

What are the alternative parent rocks for schist and gneiss?

sandstone, granite, and andesite

What is the parent material of quartzite?

quartz sandstone

What is the mineral that makes up quartzite?

quartz

What is the predominant factor for forming nonfoliated rocks?

heat

What is the parent material of marble?

limestone

What mineral makes up marble?

calcite

Index minerals

minerals that give hint to what environment the metamorphic rock was formed

Metamorphic facies

when multiple index minerals that have similar characteristics of what environment they are found

Types of geologic time

relative age and absolute age

Relative age

the age of something in comparison to something else (A is older than B)

Absolute age

the approximate age of a rock

Principles of relative age

original horizontality, superposition, lithologic correlation, fossil correlation

Principle of original horizontality

sediments are deposited in horizontal layers

Principle of superposition

the layer on the bottom is the oldest if undisturbed

Principle of lithologic correlation

when two areas have the same layers of rock, meaning that they experienced the same things

Principle of Fossil correlation

making correlations between fossils found at different sites and corresponding rock layers

Principle of Missing Time

a missing layer of rock was eroded and then new stone built on top of the previous layer

Unconformity

when rock layers don’t fit perfectly together due to a layer between them being missing

Angular unconformity

when there’s an angle difference between two layers next to each other due to a missing layer

Disconformity

when the layers above and below an unconformity are parallel

Cross cutting relationships

using two or more different formations to tell which event happened first, second, or last

Faulting

a crack in a rock that can now move independently

Folding

when pressure causes rock to fold in on itself

Half life

the amount of time needed for half the material to decay

Daughter element

when an element has gone through a half life and changed electrons

What are the Eon division?

Hadean, Archean, Proterozoic, Phanerozoic

List the eras of time in the phanerozoic eon

Paleozoic, Mesozoic, Cenozoic

List the periods in the paleozoic

Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian

List the periods in the mesozoic

Triassic, Jurassic, Cretaceous

Chemical weathering

materials are chemically dissolved and removed over time

Physical weathering

materials are physicalled broken and removed over time

Differential erosion

erosion that affects minerals differently within a rock

What type of weathering affect hot dry humid climates?

chemical weathering abundant

What type of weathering is affecting cold dry humid climates

chemical minimal, physical abundant

What type of weathering is affecting hot humid climates

chemical and physical weathering abundant

What factors speed up weathering?

water and temperature

How is soil made?

plant/fungi/animal matter, broken down minerals/rocks

What does water and carbon dioxide make?

carbonic acid (H2CO3) a weak acid

Soil horizons

the layers of dirt

O horizon

the top layer of dirt, where soil is added on top

A horizon

the second layer of dirt, nutrient rich/most productive layer

E horizon

third layer, full of insoluble minerals

B horizon

4th layer, has soluble minerals

C horizon

5th layer, partially altered bedrock

R horizon

last layer, original bedrock

3 types of soil

pedalfer, pedocal, laterite

Pedalfer

soil is mostly aluminum and iron, highly productive, where there is adequate rainfall

Pedocal

soil is mostly calcite, poor agriculturally, comes from lack of rainfall

Laterite

aka red soil, soil intermediate in both composition and productivity, found in areas of excessive rainfall (tropical/subtropical)

Factors that can cause slope failure

rock type, climate, presence of soil, time of exposure, microbiological organisms, slope steepness, altitude

Features of soil

joints, frost action/wedging, exfoliation, spheroidal weathering

Joints

cracks in the lower layers of soil after upper layers are quickly removed and water slowly increases microfractures

Frost action/wedging

water enters cracks, freezes, expands, breaks things apart

Exfoliation

rock is taken away in layers

Spheroid weathering

rocks are formed into a sphere

Mass movement

downhill movement of masses of soil, rock, or mud under the action of gravity

Creep

when rock slowly move downhill

Factors that make a place vulnerable to mass movement

steepness or instability of slopes, angle of repose, nature of slope material, amount of water present, bedding orientation

Angle of Repose

maximum angle of stability

Triggering mechanisms for landslides

rain, eathquake, deforestation, mining

Classification of mass movement

nature of materials (fine or coarse), speed of movement, nature of movement

Nature of materials mass movement

rock or sediment

Speed of movement

slow, intermediate, fast

Nature or movement

flow, slide, fall