EARTH ()

Radius:(R) 6.378 x 106 m

3924 miles

(1 R)

Mass:(M) 5.98 x 1024 kg

(1 M)

Mean Density:() 5.5 g/cm3

Unique Features: LIFE

Structure of the Earth

Deep Wells: - deepest is 12 km (7.5 miles) in Russia - temp at bottom = 190oC or 375oF !

Seismology - science of shock waves - caused by earthquakes, volcanoes, etc. - shows density and boundary of regions

Two basic types of seismic waves:

Shear (S) waves: - material displaced side-to-side

- need a solid, will not go through a liquid

Pressure (P) waves: - material is compressed

- can travel through any material

RESULTS: Crust: low density rock (2.5-3.5 g/cm3) variable thickness (5 – 50 km) rigid, brittle material

Mantle: high density rock (3.5-5 g/cm3) 2900 km thick “plastic” - hot, solid but can flow

Outer Core: liquid Iron (some Nickel) very high density (9-11 g/cm3) 2200 km thick

Inner Core: solid material; (~ 13 g/cm3 ) crystallized iron-nickel ??

Differentiation

- mixing material with different densities -lower density objects will "float" -higher density objects will "sink" - Ice floats on water - Rock floats on liquid iron

Formation of Earth: -accretion/collisions of smaller objects -great amounts of heat released -original Earth molten

Earth became differentiated: -densest elements "sink" to center

-iron, nickel -lightest elements "rise" to surface

-silicon, oxygen compounds

Today, slowly cooling off: Interior of Earth still very hot at center (> 5300 oC or 9600 oF !)

Surface of Earth

Crust of Earth is broken into plates: - 15 major plates move ~ 10 cm/yr - carried by gradual motion in mantle

➔ Plate Tectonics

- Cause of many geographic features - mountain ranges, oceanic trenches and rifts, island chains

- cause of many active features - volcanoes, earthquakes

Plate Tectonics in the past

http://www.scotese.com/earth.htm

Other processes that affect surface -Erosion, Deposition (from wind, water)

Mississippi Delta

-Impact Cratering http://www.passc.net/EarthImpactDatabase/index.html

Tswaing Crater, South Africa

-Life (Human activities)

Earth’s Surface is geologically "young" - only 10 - 100 million years old

Atmosphere

Composition: Nitrogen (N2) 78.09%

Oxygen (O2) 20.95%

Argon (Ar) 0.93%

Carbon Dioxide (CO2) 0.035% (rising)

Water Vapor (H2O) varies ( 0.4%)

But, atmospheres of Venus and Mars CO2 = 95% - 96% !!

Where is all the CO2 on Earth??

Why is there so much N2, O2, H2O on Earth??

Recycled Air

Earth’s atm. has changed since formation Action of Volcanoes:

- Outgassing -water vapor, N2, CO2, Ar

- Primary source of Earth's Water -water is predominant surface

Action of water, rain:

- dissolves CO2 , settles into rocks -Examples: Limestone

Coca-Cola, Pepsi

Action of Plant Life: (algae) - releases O2, absorbs CO2

http://www.nasa.gov/vision/universe/newworlds/ets_breath.html

Environmental Issues

Ozone (O3) Depletion

Ground Level Ozone - near surface - pollutant (crop & respiratory problems)

Ozone Layer - in middle layer (10 -35 km high) - absorbs and blocks UV from sun

Depletion of Ozone Layer - manmade Chloroflourocarbons (CFC) - reacts with and destroys O3

The Ozone Hole - sharp drop in ozone over South Pole - hole is dramatically larger since 1980

Effects of Ozone Depletion (increase UV)

- can induce skin cancer, cataracts, affect plants, animals

2006: Tied record - largest ozone hole Set record - least amount of ozone http://ozonewatch.gsfc.nasa.gov/

2015 2018

Montreal Protocol, 1987 (ratified by 191 countries)

" Perhaps the single most successful international agreement to date has been the Montreal Protocol. "

Kofi Annan, Former Secretary General of the United Nations

- phaseout of CFC by 1995 in developed countries

- total phaseout of other compounds by 2015 - but CFC takes years to reach O3 layer - CFC levels in stratosphere reducing very slowly.

- full recovery not expected until year 2050 – 2070

The Greenhouse Effect

What is it? Refers to energy (heat) gained versus

energy (heat) lost

Primary energy source for Earth ➔ SUN

- most of Sun's energy is in the form of visible light

- atmosphere is transparent to visible Light

Earth’s surface absorbs most of the energy - heats up and reradiates energy - emits infrared (IR) energy

Atmosphere is not transparent to IR - “greenhouse” gases absorb IR, heat up - slows down heat loss to space - "greenhouse effect" does not

generate heat - like a blanket slows heat loss from

Body

Greenhouse Gases: - H2O, CO2, Ozone (O3), methane (CH4),

nitrous oxide (N2O)

- avg T of Earth is 35oC (63 oF) warmer than it would be with no atmosphere. - avg T of Earth = 60 oF

But, all forms of combustion release CO2 - CO2 levels are highest in 800,000 yrs - June 2018, level hit 411.09 ppm

https://www.co2.earth/co2-ice-core-data

Consequences: Global Temperature Rise: 8 warmest yrs on record all 2005-2017 Hottest year ever: 2016 2nd hottest year: 2015 3rd hottest year: 2017 42 years since a colder than average year (1976)

http://www.sciencemag.org/content/339/6124/1198.abstract

Shrinking ice sheets: Antarctica: -127 billion tons ice per year Greenland: -286 billion tons ice per year

https://climate.nasa.gov/vital-signs/ice-sheets/

Sea level rise: - rose 6.7 inches in 20th century

- rose 1.3 inches from 2000-2010 - rose 0.7 inches from 2010-2017 - rising 0.13 inches every year, accelerating https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level Changes of Ocean chemistry: Oceans becoming more acidic as more CO2 absorbed (+30% in past 100 yrs)

https://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F

30 indicators of climate: All show long term trend to warmer climate

https://www.epa.gov/sites/production/files/2016-08/documents/climate_indicators_2016.pdf

Paris Climate Agreement (2015)

- global action plan to limit global warming to less than 1.5oC

- ratified by 195 countries - U.S. announced withdrawal in 2017