geol 11 the universe and the earth

Singularity

An infinitely small region of space with zero

volume and no dimensions

Singularity

State of the universe before the Big Bang

The Big Bang Theory

First proposed by Georges Lemaître in 1920s

The Big Bang

Not an explosion of fire

but a "superfast inflation

or expansion" in 3

dimensions

13.8 Ga (billion years ago)

age of the earth

~ 93 billion

light-years (1 light year = 9.4607 x 1012 km)

The Observable Universe

Present diameter:

1.96 million

km per sec (6.5 times faster than

the speed of light in vacuum)

The Observable Universe

Rate of expansion:

1. Abundance of primordial elements

(H and He)

2. Cosmic Microwave Background

(CMB) Radiation

3. Hubble's Law

Evidence of the Big Bang

Cosmic Microwave Background (CMB) Radiation

1965: astronomers

tried to eliminate

background "noise"

from satellite signals

Cosmic Microwave Background (CMB) Radiation

Leftover radiation

from the energy-rich

Big Bang

Hubble's Law

Edwin Hubble observed

a "redshift" in 1929

Redshift

stretching

of wavelength when

a light source moves

away from an

observer

The Nebular Hypothesis

Immanuel Kant and Pierre

Simon de Laplace, 18th century

The Nebular Hypothesis

Rotating gas-dust cloud began

to contract due to gravity

Most mass in the center -> Sun

order to the sun

Remaining matter -> asteroids

-> planetesimals -> planets

order in the nebular hypothesis

nebula

A large cloud of dust and gas in space

Nucleosynthesis

Formation of new elements

due to fusion in the Sun and

other stars

Nucleosynthesis

Process that creates new

atomic nuclei from

preexisting nucleons,

primarily protons and neutrons

Supernova

Explosion of a star

Supernova

When a star burns all of its

H and He fuel, it will

collapse into itself then

rapidly rebound outwards

Terrestrial Planets

Rocky composition: largely

silicate rocks and metals (Si, Fe,

O)

Jovian Planets

Gaseous or liquid form

• Composed of light elements (H,

He, Ar, C, O, N)

The Iron Catastrophe

Formation of a differentiated Earth

Accretion

- sticking together of dust

due to gravity

Proto-Earth

Heating

melting of materials

o Molten Earth

Differentiation

sinking of heavy

elements, rising of light elements ->

different composition on the center

and at the surface

o Differentiated Earth

1. Collision

2. Solar Radiation

3. Radioactive Heat

4. Temperature Increase from Contraction

4 Sources of Heat

Producing the molten Earth

Giant Impact Hypothesis

Collision of Earth with a Mars-

sized planetesimal to form the

Moon

Core

• Fe-rich sphere with small amounts of Ni

and other elements

• Fe-Ni alloy

• Radius: ~ 3 500 km

• ~ 16% of Earth's volume

• ~ 31% of Earth's mass

Mantle

• Still Fe-rich compared to crust, but

diluted with O, Si, Mg, etc.

• Thickness: ~ 2 900 km

• ~ 83% of Earth's volume

• ~ 68% of Earth's mass

Crust

• Solid outer shell

• Varying thickness:

o Continental: 15 - 60 km

o Oceanic: 3 - 15 km

• Less than ~ 1% of the

Earth's mass and volume

1. Inner Core

2. Outer Core

3. Lower Mantle

4. Asthenosphere

5. Lithosphere

Layering by Mechanical Properties

solid

liquid

solid

solid but mobile

solid and rigid

• Lithospheric Mantle

• Crust

1. Inner Core -

2. Outer Core -

3. Lower Mantle- 4. Asthenosphere -

5. Lithosphere -

response of each layer

to a dominant variable at a

certain depth

Layering by Mechanical Properties Cause:

melting

Temperature increase

solidification

Pressure increase

1. Seismic Waves

2. Xenoliths

3. Abundance of Fe in the Solar System

4. Earth's magnetic field

Evidence of Earth Layering

P-waves

both solid

and liquid medium

S-waves

solid

medium

Shadow zones

no

waves or only certain

waves recorded

Xenoliths

- mantle rocks entrained by ascending magma

and brought up to the surface

Earth's magnetic field

generated by the flow of the liquid

outer core

Isostasy

• Equilibrium between the lithosphere and asthenosphere

• Explains why topographic differences exist

1. Pratt's Theory

2. Airy's Theory

3. Flexural Theory

Theories of Isostasy

Pratt's Theory

• Assumption: Equal depth of the lithosphere

• Elevation Differences: Due to differences in density

Airy's Theory

• Assumption: Equal density

• Elevation Differences: Due to depth of roots

o Deep root -> high elevation

o Shallow antiroot -> low elevation

Flexural Theory

• Accounts for the elasticity of the

lithosphere

• Local load -> regional downwarping

o Example: ice sheets

Eratosthenes, 240 BC

- first to measure

Earth's circumference

40 076 km

Equatorial

40 008 km

Polar

1. Continents

2. Ocean Basins

Earth's Large Scale Features

Mountain Belts

Bands of high elevation above sea level (on land)

Plains

Extensive areas of low elevation above sea level (on land)

Mid-Oceanic Ridges

Extensive ranges of high elevation below sea level (in the

ocean)

Trenches

• Deep regions of the ocean floor

• Features formed in subduction zones

Continental Margin Features

Landforms in the transition zone between continents and

ocean basins

a. Continental Shelf

b. Continental Slope

c. Continental Rise

Continental Margin Features

Abyssal plains

Seamounts

Guyots

Seafloor Features

Abyssal plains

vast,

flat expanse of ocean

floor

Seamounts

submarine

volcanic landforms

Guyots

underwater

plateaus from inactive

seamounts