Midterm 1

What is geocognition

the art and science of geologizing

the nature of scientific inquiry for geology

deals with large and complex spatial scales, deals with immense time scales, deals with incomplete evidence

Principle of Uniformitarianism

Geological processes and natural laws that operated today have acted throughout geologic time

2 types of scientific methods

1\. inductive (barconian) method

2\. Deductive (Darwinian) method

What is the inductive method

Collecting a bunch of data but with no real hypothesis

What is the deductive method

collection of data with a theory

4 steps in deductive scientific method

1\. collection of scientific data

2\. developmental of one or more working hypothesis to explain the facts

3\. development of observations and experiments to test the hypothesis

4\. acceptance, modification or rejection

why is the collide impact the source in which dinosaurs went extinct?

1\. geochemical anomalies are world-wide

2\. craters

What are tectonic plates

Sections of the Earth's crust that move due to convection currents.

Where do most earthquakes occur?

edges of tectonic plates

Theory of Plate Tectonics

The theory that pieces of Earth's outer layer are in constant motion

4 plate tectonic concepts

1\. Outer portion (shell) of the Earth is composed of rigid layers called plates

2\. The plates move slowly

3\. Most large-scale geological activity occurs at plate boundaries

4\. Interior (center) of plates are relatively geologically quite

What is an earthquake?

the vibration of Earth produced by the rapid release of energy

2 types of wave transmission of solid waves

1\. primary waves

2\. secondary waves

Primary Waves (P-Waves) Characteristics (4)

\- first wave generated by the earthquake

\- travel parallel

\- go through all mediums

\- p waves are faster than s waves

Secondary Waves (S Waves) characteristics (2)

\- perpendicular motion

\- only go through solids

What does snell's law say?

waves will refract when mediums change

law of reflection

the angle at which the wave falls on the surface is equal to the angle at which it’s reflected

3 major interior boundaries of the earth

1\. crust-mantle boundary

2\. core-mantle boundary

3\. Core

What is Moho discontinuity

boundary between crust and mantle

what is the crust-mantle boundary based on?

the observation that seismic velocity are slower in the crust then the mantle

what is the core-mantle boundary based on?

observation that P-waves disappeared 105° from the earthquake and reappear at about 140°, this belt is named P-wave Shadow Zone

What is the P-wave shadow zone

area where earthquake is not felt

what info does the S-wave shadow zone tell us about the core?

the outer core is liquid because S-waves can’t travel through liquids

What is the S-wave shadow zone

areas with no S-waves

how are the layers of earth defined? (2)

1\. Chemistry/composition

2\. Physics/mechanics

layers of the earth based on chemical composition

crust, mantle, core

layers of the earth based on physics composition

lithosphere, asthenosphere, mesosphere

The lithosphere is made up of

cool, strong and brittle crust and upper mantle

two examples of lithosphere

1\. oceanic

2\. continental

the asthenosphere is made up of

partially melted and ductile upper mantle

the mesophere is...

strong and hot

the geothermal gradient

the rate of change in temperature with depth

What is conduction

Change in temps as we move through the solid Earth

3 reasons why the core is heated

residual heat from big bang, radioactive decay, exothermic reaction of liquid to solid in core

what are the 2 requirement of the core to produce magnetic field?

composed of material that conducts electricity, mobile, an inner core that rotates faster than the earth

What drives mantle convection?

Heat in the deep mantle and core and gravity

what happens in the mantle convection?

circulation driven by rising hot material/sinking cooler material

What is slab pull

the pulling of a tectonic plate as its edge subducts deep into the mantle

What is slab Push

the pushing of crust resulting from elevated position of ocean ridge system, causing crust to slide down

what materials form the plate tectonic

Si, Al, K, Na and Ca --> felsic material

What are the asthenosphere and mesosphere made of?

Mg & Fe --> mafic material

What are the 4 characteristics to define a substance as a mineral?

naturally occurring, solid, definite chemical composition, crystal structure

3 conditions that determine the type of mineral formed

relative abundance of elements, temp & pressure at time, size & charge of atoms/ions

What are polymorphs?

minerals that have the same chemistry but different structure

what are the big 8 elements in classification of minerals

potassium, oxygen, calcium. aluminium, silicon, sodium. iron and magnesium

What is magma?

molten rock within the earth

What is lava?

Liquid magma that reaches the surface

3 components of magma

liquids(melt), solids(crystals/minerals), gases(volatiles)

Where does igneous rock come from?

1\. liquid magma

2\. magma cools, and forms a crystalline structure

3\. cooled & crystallized magma is now igneous rock

if the rock is crystallized on the surface, what is it called?

extrusive/ volcanic

if the rock crystallized underneath the subsurface, what is it called?

intrusive/ plutonic

Bowen's Reaction Series

pattern that illustrates the order minerals crystallize from cooling magma according to their chemical composition and melting point

2 ways bowen's series crystallization occurs

1\. continuous

2\. discontinuous

Bowen's Reaction Series ends inwhat type of rock?

quartz

bowen's reaction series assumes 3 things, what are they?

closed system, early minerals remain in contact with magma, full range of igneous rocks could be produced from the same mafic magma

What are the 3 things needed to form magma?

temp increase, add a volatile, pressure decrease

4 Types of magma composition

mafic, felsic, intermediate (andesitic) composition,, ultramafic

mafic magma characteristics

silica poor, low viscosity, releases volatiles, high density, high temperature, basalt

felsic magma characteristics

silica rich, high viscosity, retains volatiles, low density, low temperature, granite

What is intermediate composition

the composition of igneous rocks lying between felsic and mafic

What is ultramafic magma

Igneous rocks with low silica content and very high levels of magnesium and iron. Periodite, dunites, and doirite are examples.

what are the 3 factors affecting crystal size?

rate of cooling, amount of silica, amount of dissolved gases

How does the rate of cooling affect crystal size?

slow rate= fewer but larger crystals

fast rate= many small crystals

very fast= forms glass

how does silica affect crystal size?

less silica = smaller crystal sizes

how does gases affect crystal size?

results in holes in rocks

Phaneritic characteristics

coarse-grained, crystals are large, formed by slow cooling (intrusive)

Aphanitic characteristics

fine grained, formed by fast cooling

Porphyritic characteristics

large and small crystals; slow, then rapid cooling

Glassy

crystal unable to form, rapid rate of cooling prevents crystals from forming

What is obsidian

volcanic glass

What is pyroclastic

expulsion of ash, cinders, bombs and gases during an explosive eruption

What is pegmatitic

Very large crystals formed by extremely slow cooling, or in the presence of water.

What is sediment

small, solid pieces of material that come from rocks or living things

sedimentary processes 5 steps

weathering, erosion, transport, deposition, lithification

4 factors that control weathering

parent rock, climate, soil/vegetation, time

What is clastic sedimentary rock

rock that forms when fragments of preexisting rocks are compacted or cemented together

grain size suggest what of a rock?

the proportional energy level of transport medium

What is grain sorting

grain size variability in a sample of sediment or rock

What is well sorted sediment

homogenous grain sizes

What is poor sorted sediment

combination grain sizes

grain shape tells us what about a rock?

how far grain traveled and energy level of transportation

What is mudstone

Clay to silt-sized particles in thin layers

What does red mudstone suggest?

Fe & O rich

What does green mudstone suggest?

Fe and O poor

What does black mudstone suggest?

not enough O to decompose organic matter

What is sandstone

a sedimentary rock formed by cementing grains of sand over time

What are conglomerates

round particles

What is breccia

angular particles

What is limestone

a sedimentary rock composed of calcium that was deposited by the remains of marine animals

factors affecting limestone precipitation (3)

solubility, temp, cold water --> holds more CO2 than warm water, agitation of water, and water depth

What is Chert/Flint

sedimentary, composed of quartz with very fine crystalline texture.

What are evaporites

sedimentary rocks formed from minerals left after water evaporates

What is coal

solid fossil fuel that is formed from the concentrated remains of plants over very long periods of time.

What is metamorphism

process where one type of rock changes into metamorphic rock because of chemical processes or changes in temperature and pressure

what 3 rocks are metamorphic rock produced?

igneous, sedimentary, other metamorphic rocks

3 factors that controls metamorphism

temp, pressure, fluidity

2 type of pressures on a rock

lithostatic /confining, directed

What is lithostatic/confining pressure?

rock is being pushed equally from all directions, more dense, but shape does not change

What is directed pressure?

pressure is put on one side and changes shape