Earth 119 Exam 1

Age of the Universe

13.7 billion years old

Big Bang Theory

The theory that the universe originated in a huge explosion that released all matter and energy

Doppler shifts

How we know that the universe is still expanding

First 2 elements

hydrogen and helium

Nebular Hypothesis

Kant, the theory that explains the formation of the Solar System

1. Gravitational attraction of denser gas clouds draw in more gas

2. This led to formation of a spinning accretionary disk (flattened due to gravity)

3. Gravitional collapse led to formation of proto-star, a dense hot ball of gas at the center of the accretionary disk

4. Once high enough pressures and temp are reached, fusion reactions begin forming heavier elements and the star ignites

Age of Earth

4.6 billion years old

Nucleosynthesis

The natural formation of nuclei as a result of fusion and other nuclear processes; the formation of elements more complex than the hydrogen atom

Planetesimal

a body that could or did come together with many others under gravitation to form a planet

Terrestrial vs Jovian planets

Their main difference is their composition; Terrestrial planets are covered with solid surfaces while jovian planets are characterized by gaseous surfaces. These terrestrial planets in our solar system are Mercury, Venus, Earth, and Mars. The jovian planets are Jupiter, Saturn, Uranus, and Neptune

Differentiation of Earth

As Earth developed, denser materials such as molten iron sank deep to its center and less dense materials were forced to the outer layers; Crust, Lithosphere, Asthenosphere, Mantle, Liquid outer core, Solid inner core

Density of Earth

5.5 grams/cubic centimeter (average)

Density of Water

1 g/cm3

whole earth

Iron, oxygen, silicon, magnesium, nickel, sulfur, calcium, aluminum

8 abundant elements of the Earth's crust

Oxygen, silicon, aluminum, iron, magnesium, calcium, potassium, sodium

Radius of Earth

6371 km

Circumference of Earth

40,000 km

Deepest depth in the ocean

11,000 meters (Challenger Deep)

Highest elevation on Earth

8850 km (Everest)

Ocean coverage:Land coverage

70%:30%

Average depth

12,430 ft

Depths of Earth's layers

Core - 10-70km

Upper mantle (lithosphere) - ~700km

Lower mantle (asthenosphere) - ~3000km

Outer core - ~5000km

Inner core - 6371km

Convection

The transfer of heat by the movement of a fluid or gas; it drives the motion of tectonic plates

Continental drift

Wegner 1915, the hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations (wasn't accepted until the 60s)

Evidence for continental drift

1) continental fit 2) similarity of plant/animal fossils 3) similarity of rock types, glacial remains, mountain ranges 4) paleomagnetism

Seafloor spreading

the process by which new oceanic crust forms along a mid-ocean ridge and older oceanic crust is pushed towards the continents; it is the best proof of cont. drift because it captures polarity of the time the crust formed, thereby proving the process of convection

Deep sea drilling

Tells us the age of ocean floor, rocks are believed to be youngest when nearest to the ridge

Oldest ocean rock

150-170 million years old (Jurassic age)

Divergent boundary

The boundary between two tectonic plates that are moving away from each other (due to decompression melting)

Think of: Mid-ocean ridges

Convergent boundary

A tectonic plate boundary where two plates collide, come together, or crash into each other

Think of: Subduction (Ocean-Cont.) or Island chains (Ocean-Ocean), EQs from colliding, volcanoes

Transform boundary

The boundary between tectonic plates that are sliding past each other horizontally

Think of: Faults, EQs from slipping back into place

Earth's magnetic field

Magnetic lines of force from Earth's polar north and south, acting like a giant magnet caused by the flow of convection within Earth's liquid outer core

Geothermal

of, relating to, or using the natural heat produced inside the Earth; it changes as you get deeper (changes temp./pressure)

Inclination

Latitude where a rock was formed

Declination

Difference in angle between the magnetic North Pole vs the North Pole

Distribution of Earthquakes

Earthquakes mostly happen on plate boundaries,

the ones that don't are caused by human activity such as underground mining or oil extraction

Examples of divergent boundaries

Mid Atlantic Ridge, Great Rift Valley in Africa

Examples of convergent boundaries

collision:

Ex. Himalayan Mtns., Ural Mtns., Southern Appalachians

ocean-ocean subduction:

Ex. Pacific plate subducts under the Eurasian plate and create the Japan and the Japan Trench, island arcs

ocean-continental:

Ex. Nazca plate subducts under the S. American plate creates the Peru-Chile Trench and the Andes Mtns.

Examples of transform boundaries

San Andreas Fault and Wallace Creek

P-waves vs S-waves

P-Waves: compression waves, Pass through solids, liquids (magma), and gasses

S-Waves:

Secondary Wave (Shear Wave)

Slow wave, not as fast as the P-wave, arrives at a seismic station second

Shake wave, vibrates side-to-side

only travels through solid layers

Isostasy

Less dense continents (felsic) "float" higher than oceans (mafic) which "sink" into the underlying asthenosphere in order to balance out density

Average seafloor spreading rate

~2-15 cm/yr or 20-150mm/yr

Wilson Cycle

The cyclical opening and closing of ocean basins caused by movement of the Earth's plates

Mineral (5 defining characteristics)

- Naturally occurring/homogeneous

- Definable chemical composition

- Ordered arrangement of atoms to form a crystalline solid

- Possess distinct physical properties

- Inorganic

Structure of an atom

nucleus made up of protons (+) and neutrons; the electrons (-) make up the surrounding area

Atomic number

number of protons

Atomic weight

number of protons + neutrons

Chemical reactivity

defined by number of electrons, the ability of elements to combine and chemically bond with each other

valence electrons

The electrons in the outermost shell (main energy level) of an atom; these are the electrons involved in forming bonds

Cation

A positively charged ion

Antion

A negatively charged ion

Properties of minerals: Luster

the way light interacts with the surface of a mineral; a range of terms are used to describe lustre, such as earthy, metallic, greasy, and silky

Properties of minerals: Cleavage

the way some minerals break along certain lines of weakness in their structure

Properties of minerals: Crystal habit

the characteristic external shape of an individual crystal or crystal group; recognizing the habit may help in identifying a mineral

Properties of minerals: Hardness

measured by the resistance which a smooth surface offers to abrasion (Mohs scale); the degree of hardness is determined by observing the comparative ease or difficulty which which one mineral is scratched by another

Properties of minerals: Density

a property of all matter that is the ratio of an object's mass to its volume

Crystallization

The process by which atoms are arranged to form a material with a crystal structure (how minerals are formed)

Intrusive igneous rock: Coarse-grained

- Noticeable, large crystals

- Slow cooling/rate of crystallization

- Cooled from magma within Earth's mantle

Intrusive igneous rock: Fine-grained

- Crystals are too small to be seen by the unaided eye

- Fast cooling/rate of crystallization

- Cooled from magma within Earth's mantle

Extrusive igneous rock: Coarse-grained

- Noticeable, large crystals

- Slow cooling/rate of crystallization

- Cooled from lava at Earth's surface

Extrusive igneous rock: Fine-grained

- Crystals are too small to be seen by the unaided eye

- Fast cooling/rate of crystallization

- Cooled from lava at Earth's surface

Magma composition: Felsic

- Color: pink/white/light

- High silica content

- High sodium and potassium content

- Low iron, magnesium, and calcium content

- Low temp (~700 C)

- Granite (coarse), Rhyolite (fine)

- Quartz, K-feldspar, Muscovite mica, sodium rich on Bowen's reaction series

Magma composition: Intermediate

- Color: grey/purple

- Average silica content

- Average sodium and potassium content

- Average iron, magnesium, and calcium content

- Average temp (~900)

- Diorite (coarse), Andesite (fine)

- Biotite - Amphibole on Bowen's reaction series

Magma composition: Mafic/Ultramafic

- Color: black/green/dark

- Low silica content

- Low sodium and potassium content

- High iron, magnesium, and calcium content

- High temp (~1000-1100)

- Gabbro (coarse), Basalt (fine), Peridotite (UM coarse)

- Pyroxene on Bowen's reaction series; Olivine, calcium rich on Bowen's reaction series (UM)

Valence groups

row 1 = 1 valence electron until rows 3-12 (transitional metals) = 3-12, then at row 13 = 3 valence electrons and so on

Silicate ion

SiO4 4-

Different types of Silicate polymorph minerals (least complex to most complex)

Isolated tetrahedra - olivine

Single chains - pyroxene

Double chains - amphibole

Sheet - muscovite

Framework - feldspar

Rocks vs. Minerals

A mineral is a naturally-occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties. A rock is a naturally occurring aggregate of minerals and/or mineraloids. Rocks do not have a definite chemical composition.

intrusive rock

Igneous rock that forms when magma hardens beneath Earth's surface

extrusive rock

igneous rock formed from lava that erupted onto Earth's surface

Formation of magma: decompression melting

Partial melting; hot mantle rock rises toward the divergent plate boundary (area of less pressure) the reduction in overlying pressure enables the rock to melt, leading to magma formation

Formation of magma: dehydration melting

As an oceanic plate is subducting, the water is squeezed out and up, into the mantle wedge. As this hot water interacts with the rocks above, the melting point of the rocks is lowered, partial melting occurs, and plutons are forced towards the surface

- Water decreases melting temp. so geotherm P/T chart changes

Rodinia

Oldest supercontinent reconstructed with greatest accuracy, 1.1 billion years old

Pangea

Another important supercontinent, 250 million years old

Bowen's Reaction Series

From high to low temp:

silica, sodium, and potassium increase

Iron, magnesium, and calcium decrease

Olivine, pyroxene, amphibole, biotite mica, muscovite, quartz, orthoclase feldspar

High temp=1200C

Low temp=600C

Polymorphs

Same chemical composition but different arrangement of atoms in the crystalline structure

Ionic bonds

Own electrons

Most common type

Not very strong

Covalent bonds

Share electrons

Strong

Slower the rate of crystallization

The larger the crystals

Quartz

SiO2

Olivine

(Mg,Fe)2SiO4

Isolated tetrahedra

Pyroxene

Single chain

Amphibole

Double chain

Muscovite mica

Sheet

Feldspar

framework silicate

Quartz another framework

K-Feldspar

KAlSi3O8

Na-Plagioclase

NaAlSi3O8

Ca-Plagioclase

CaAl2Si2O8

igneous rock

rock that forms when magma cools and solidifies

Hotspots

Magma pushes through the mantle and creates zones of weakness

Stationary hotspots under moving plates