GEO 303 Exam 1 Shanahan

meteorites

hypothesized to represent the leftover "bits" from the time of formation of the solar system. They are likely pieces of planetismals and eartly Earth bodies - oldest ones date to 4.567 Ga

dating meteorites

done by radiometric techniques. the natural decay of small amounts of radioactive elements in these bodies occurs at a constant rate - and can be used to estimate the time since formation.

age of the universe

~13.8 Ga

the doppler effect

an observed change in the frequency of a wave when the source or observer is moving

redshift

shift of light to a longer wavelength as it moves AWAY

blueshift

the displacement of the spectrum to shorter wavelengths in the light coming from distant celestial objects moving toward the observer.

earth's interior

inner core, outercore, menosphere, aesthenosphere, lithosphere

core = Fe/Ni

mantle = ultramafic

crust = felsic and mafic

aesthenosphere

a layer of softer, weaker rock beneath Earth's lithosphere, which can flow slowly

lithosphere

the rigid outer part of the earth, consisting of the crust and upper mantle

divergent plate boundary

an area beneath the ocean where tectonic plates move away from each other, new lithosphere created (used to date oceanic crust)

Mid-Ocean Ridge or coninental rifting

convergent plate boundary

an area where plates move toward one another and collide, lithosphere consumed

subduction and continental collision

volcanic arc

a curved line of volcanoes that forms parallel to a plate boundary

Wadati-Benioff zone

a sloping band of seismicity defined by intermediate- and deep-focus earthquakes that occur in the down-going slab of a convergent plate boundary.

transform plate boundary

the boundary between two plates that slide past each other (oceanic and continental)

hot spot volcanism

the creation of volcanoes on a planet's surface caused by a reservoir of hot magma in the planet's mantle under a thin part of the crust

Wegener's hypothesis

all the continents were once joined together in a single landmass and have since drifted apart

1. fit of the continents

2. distribution of climate belts

3. matching geologic units

4. fossils

paleomagnetism

the study of changes in Earth's magnetic field, as shown by patterns of magnetism in rocks that have formed over time

true polar wander

actual movement of magnetic poles through time, relative to poles of rotation. can be dramatic in short time but less important over longer term.

inorganic

not consisting of or deriving from living matter.

organic

of, relating to, or derived from living matter. contains carbon.

precipitates

the solid materials left behind after a liquid evaporates.

form as solubility of dissolved ions in solution changes (pH or pressure change)

EX) Calcite (CaCO3) stalactites, Quartz geode

minerals

a solid inorganic substance of natural occurrence. ordered atomic structure

rock

any naturally occurring solid. most but not all contain minerals

olivine

highest temperature mineral. sugary and green. most likely to weather. 0 tetrahedra bonded by covalent bonds.

quartz

SiO2. lowest temperature mineral, least likely to weather

igneous rock

a type of rock that forms from the cooling of molten rock at or below the surface

The most important chemical variation is changes in the amount of silica

mafic low silica

felsic high silica

sedimentary rock

a rock that forms from compressed or cemented layers of sediment

metamorphic rock

a rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions

crystal habit

the shape in which a mineral's individual crystals or aggregates of crystals grow.

cleavage

a mineral's ability to split easily along flat surfaces.

unit cell

the smallest group of particles within a crystal that retains the geometric shape of the crystal

mineral polymorphism

ability for minerals with the same composition to crystalize with more than on structure

ionic bond

formed when one or more electrons are transferred from one atom to another

strength of the bond will depend on distance between cations and anions

packing and bond strength are thus related to sizes of anions

generally low hardness and sometimes water soluble

if it's made from a metal and a non-metal...

covalent bond

a chemical bond that involves sharing a pair of electrons between atoms in a molecule

no electrons are acquired or given up

strong bond

tend to be hard minerals

if it's made from two non-metals..

metallic bond

a bond formed by the attraction between positively charged metal ions and the electrons around them

strong bonding

tend to be soft and conductive

van der waals

atom are tied together by 'residual electronic charges'

very weak bonding/attractive forces

tend to be very soft

graphite is an example

pyroxenes

single-chain silicate minerals

family of minerals

often with iron, makes them dense, hard, and dark

augite

framework silicates

all of the oxygens are shared between adjacent tetrahedra

no need for any cations

very strong material

quartz, feldspar

Bowen's Reaction Series

sequential, predictable, dual-branched pattern in which minerals crystallize from cooling magma

Olivine->Pyroxene->Amphibole->Biotite->K-Feldspar->Muscovite->Quartz

silicate

SiO4 4- anion as a building block in its crystal structure

magma

liquid rock (usually mostly silicate)-temperatures from 700 degrees C to 1300 degrees C - inside the Earth

intrusive rocks

plutonic. magma cools beneath the earth's surface

extrusive rocks

volcanic. lava cools on Earth's surface

no crystals

quenched, above ground, under water, ice

small crystals

cooled quickly, above ground

large crystals

cooled slowly, below ground

large AND small crystals

cooled slowly, then quickly. below then above ground

mafic

describes magma or igneous rock that is rich in magnesium and iron and that is generally dark in color

low viscosity

high melting temp

oceanic crust

low gas content

felsic

describes magma or igneous rock that is rich in feldspars and silica and that is generally light in color.

high viscosity

low melting temp

high gas content

continental crust

xenolith

a piece of rock within an igneous rock that is not derived from the original magma but has been introduced from elsewhere, especially the surrounding country rock.

dike

a slab of volcanic rock formed when magma forces itself across rock layers VERTICAL

sill

a slab of volcanic rock formed when magma squeezes between layers of rock HORIZONTAL

laccolith

a mass of igneous rock, typically lens-shaped, that has been intruded between rock strata causing uplift in the shape of a dome.

batholith

a mass of rock formed when a large body of magma cools inside the crust

shield volcano

a wide, gently sloping mountain made of layers of lava and formed by quiet eruptions

stratovolcano

a composite volcanic cone built of interlayered lava flows and pyroclastic materials

cinder cone volcano

a small, steeply sloped volcano that forms from moderately explosive eruptions of pyroclastic material

andesitic lava flows

type of lava flow; higher silica content, greater viscosity, forms a large mound above the vent out of a volcano.

crater

a bowl-shaped area that forms around a volcano's central opening

caldera

gigantic volcanic depression (Crater Lake)

pyroclastic flow

the flow of ash, cinders, bombs, and gases down the side of a volcano during an explosive eruption