The Earth: Objectives
Overall physical properties
How Earth's atmosphere warms and protects us
Current model of Earth's interior- and how we know
Continental drift, evidence
Earth's magnetosphere, evidence
Gravity and the oceans, evidence
Interior of the Earth
Average rearth =5500 kg/m3
r water =1000 kg/m3
r rock =2000-4000 kg/m3
r interior = ? kg/m3
Seismic Waves
Differentiation
Why Differentiation?
Radioactivity
Plate Tectonics
Evidence of Plate Tectonics
Evidence of Plate Tectonics
Evidence of Plate Tectonics
Magnetosphere
Magnetosphere
Earth's Atmosphere
Temperature changes with altitude
Mixture of gases:
N 78% by volume, O 21%, A 0.9%, CO 0.03%
Half of the atmosphere lies within 5 km of the surface
99 % of the atmosphere lies within 30 km of the surface
How the Earth's Atmosphere Heats Up
Surface heating by visible light from Sun
Convection transports heat (hot air rises)
Clouds, turbulence
Atmosphere blocks out harmful radiation like X-rays, UV, gamma rays
How the Earth's Atmosphere Heats Up
Ozone layer- absorbs UV and IR light
Ozone is a molecule of 3 bound oxygen atoms
Earth radiates IR
IR can be trapped on Earth by atmosphere
Greenhouse effect: the partial trapping of IR light by the CO2 H2 O in Earth's atmosphere
Why is the Sky Blue?
Origin of the Earth's Atmosphere
Primary atmosphere - When Earth first formed out of light gases
hydrogen, helium, methane, ammonia, water vapor atmosphere
Most common gases in solar system
These gases escaped in the first ½ billion years
Secondary atmosphere- outgassed from volcanos
water vapor, methane, carbon dioxide (CO2), sulfur dioxide, nitrogen compounds (ammonia, nitric oxide, etc.)
Origin of the Earth's Atmosphere Cont.
UV light breaks up molecule, especially hydrogen-rich
Hydrogen escapes Earth
Nitrogen liberated from compounds
As Earth cooled, water condensed became oceans
Oxygen is very reactive
Sulfur dioxide and carbon dioxide that settle out of atmosphere
Carbon and sulfur dioxides are absorbed by rocks and get dissolved oceans, plants use carbon dioxide
Atmosphere becomes mostly nitrogen
Where was this photo taken?
Tidal Effects
Tides are related to gravity
Strength of tidal force is related to
Moon is most important to Earth's tides
Tidal Effects
Moon