Chapter 1 + Interlude D

Slow Geologic Processes

• Mountain Building

• Glacier formation

• weathering & erosion

Fast Geologic Processes

• Earthquakes

• Landslides

• Volcanoes

The Solar System

• Sun is 99.85% of solar system mass

• Eight planets

• Their Satellites

• Smaller Bodies

  • Dwarf planets

  • Asteroids

  • Comets

  • Meteoroids

Inner vs. Outer Planets

• Inner Planets

  • Mercury, Venus, Earth, Mars

  • Smaller

  • Rocky

• Outer Planets

  • Jupiter, Saturn, Uranus, Neptune

  • Gas giants

  • Larger

Galaxies

• Come in different shapes and sizes

• Earth is located within the Milky Way

  • All visible stars are within the Milky Way

The Big Bang

• 13.8 billion years ago, all energy and matter of the universe existed in a hot and dense state

• Began a cataclysmic explosion

• Everything continued to expand, cool, and evolve

• First stars formed about 200 million years later, composed of hydrogen and helium

• Stars have recycled and produced heavier elements over time

• First galaxies formed ~12.7 Billion years ago

What is the evidence of the Big Bang?

1. Redshift of Galaxies

2. Microwave Background Radiation

3. Mixture of Elements

What is the electromagnetic spectrum?

• Energy travels through space via electromagnetic radiation

• All objects in the universe emit electromagnetic radiation

• The type of radiation an object emits depends on its temperature

What is the Redshift?

• The light from many galaxies is stretched slightly and appears redder than it would be otherwise

  • “Lower” and farther light means more red, while “higher” and closer light means more blue

• Redshift shows that universe is expanding, with galaxies moving farther and farther from the universe’s starting point

Cosmic Microwave Background Radiation

• Discovered in 1964 by Robert Wilson & Arno Penzias

• Essentially microwave radiation that fills the universe, creating a faint glow around the universe that has been decreasing in brightness as the universe stretches

Mixture of Elements

• The chemical composition of the universe is dominated by Hydrogen and Helium, produced in the Big Bang

• The remaining chemicals are produced by stars and are a low percentage of the universe’s overall mass

How did the first stars come about?

• As the universe cooled & expanded, atoms began to bond

• Hydrogen molecules were formed

• Gravity collected matter and began the process of making a star

How does Stellar Birth work?

• Stars begin as nebulae, clouds of interstellar gas & dust

• Usually molecular clouds, which are cold and dense enough for hydrogen atoms to bond to hydrogen molecules

• The matter clumps together until its massive enough to contract, and form a star

What is Stellar Nucleosynthesis?

• Formation of new elements via nuclear reactions

• In the stars’ center, atoms are taken apart by atomic collisions, altering the atomic structure and releasing an enormous amount of energy (nuclear fusion)

• Mostly converting Hydrogen into helium

• Formed elements 1-26 (Ending at Iron)

• Star size depends on the type of nucleosynthesis occurs

What are the types of Nucleosynthesis

• Small Stars

  • Hydrogen to Helium

• Medium Stars (Sun-size)

  • Hydrogen to Helium to Oxygen & Carbon

• Massive stars (5x the Sun-size)

  • Hydrogen to Helium to Oxygen & Carbon to Neon, Sodium, Magnesium, Sulfur, and Silicon

What is a Supernova?

• When a massive star goes supernova, it creates all natural elements heavier than iron which forms the basis for life

• The elements disperse in space and then condense, becoming new stars and solarsystems

Star Burnout & Death

• Eventually fusion in a star’s core runs out of fuel

• Star collapses under the force of its gravity

• Ultimate fate of the star depends on its mass

What is the Nebular Hypothesis?

• A solar nebula began to compress and collapse, forming a rotating accretionary disc

• A protosun forms at the center, where it is the hottest

• The rotating disc begins to cool & condense

• Material collides to form boulder-sized planetesimals

• Plantesimals accrete to form protoplanets

Formation of Inner Solar System

• Temperatures were very hot

• Planetesimals were made of metals & rocky materials

• Formed the terrestrial planets

Formation of Outer Solar System

Temperatures were cooler

Gases condensed into ice

Formed Jovian planets

What is an Asteroid & The Asteroid Belt?

• An asteroid is planetesimals left over from formation of the solar system

• Most orbit within the region between Mars & Jupiter

  • The asteroid belt

What are comets & where do they come from?

• A comet is a small body that generally revolved around the sun in an elongated orbit

• Is made of loose collection of rocky materials, dust, water, ice, and frozen gases

• They come from the Kuiper belt (beyond Neptune) and the Oort Cloud, a spherical shell around parts of the solar system

Meteors

• Light phenomenon seen when a meteoroid enters in the atmosphere

Meteoroid

• Small solid particles that have orbits in the solar system (in space)

Meteorite

• A meteoroid that survives travel through the atmosphere to land on earth

• Thought to be representative samples of what formed the early solar system

• believed to have solidified at the same time as earth (4.5 to 4.6 billion years old)

What is on the lunar surface?

• Marias (Lowlands), dark areas formed from impacts and lava flows

• Highlands, bright densely cratered areas making most of the Moon’s surface

What is the Giant Impact Hypothesis?

• How the moon came to be:

  • During middle to late stages of Earth’s accretion a Mars-sized body impacted the Earth

  • A shower of debris from both bodies went into space

  • The impact sped up the earth’s rotation and tilted the earth’s plane 23 degrees

  • Earth reformed and the moon aggregated from the debris

  • The theory is supported by 4.47 billion yo moon rocks brought by apollo astronauts

What was going on in Early Earth (Layer formation)?

• Earth accreted about 4.6 BYA

• As Earth cooled, layers of different elements formed

• Layers were naturally sorted by density & gravity

  • Differentiation/density Stratification

  • Lower density materials form concentric circles around core

  • Low density gases pushed to surface to create Earth’s atmosphere (water vapor, CO2, hydrogen)

Differentiation/Density stratification flow

Lowest Density - Silicon

Aluminum

Nickel

Highest Density - Iron

Density equation

D = mass / volume

How do we know Earth’s interior has varying density?

From seismic waves, bending with increasing density through the earth

What are the types of seismic waves?

• P-waves

  • Compressional

  • Fastest

• S-waves

  • Shear

  • Cannot travel through liquid

How to we know the earth has a liquid outer core?

• S-waves cannot travel through it

What are the two ways to characterize Earth’s layers?

Chemical and Physical States

Earth’s Internal Structure: Chemical

• Crust

• Mantle

• Core

Crust

• Avg 30km thick

• Low density

• Silicate rocks: granite and basalt

• Two types

  • Continental

  • Oceanic

Oceanic vs Continental crust

Oceanic

• Mostly basalt (fine grained igneous rock)

• Darkly colored

• Higher density

• rich in silicon, oxygen, and magnesium

Continental

• Mostly granite

• Light colored

• Lower density

• rich in aluminum, silicon & oxygen

Mantle

• 30km to 2900km thick

• Higher density: 4.5gm/cm3

• Iron and magnesium rich silicates

• Separated from crust by Moho

Core

2900km to 6371 km thick

Highest density: 13g/cm3

Mostly iron and nickel

Outer core and inner core are compositionally the same

Earth’s internal structure: Physical

1. Lithosphere

2. Asthenosphere

3. Mesosphere

4. Outer Core

5. Inner Core

Lithosphere

• Avg 100km depth

• Cool, rigid, brittle

• Crust, and upper mantle

Asthenosphere

• 100km - 700km depth

• Hot, plastic (flows), partially melted

• Upper mantle

Mesosphere

• 700km - 2900km

• More rigid because of pressure, some flow

• Mid and lower mantle

Outer Core

Extremely Hot

Liquid, flows

Inner Core

• Extremely hot

• Rigid, no flow

What is the geothermal gradient?

• The rate of change of temperature correlated with depth into the earth

• Temperature and pressure increase with depth inside the earth

• Earth’s internal heat come from residual heat from formation and radioactive decay