Download Earth Atmosphere Surface Features

Earth
Crust (3 g/cm3) - made of silicate (SiO2 ) based rocks
Mantle (3 - 5 g/cm3 ) - 2900 km thick layer; location of lithosphere
& asthenosphere
Core (10.5 g/cm3 ) - liquid Fe/Ni shell surrounding solid Fe/Ni center
Atmosphere
Composition – Nitrogen (78%), Oxygen (21%), CO2 (0.037%), H2O (0.25%)
Ozone Layer ~ 25 km above surface
Surface Features
Earth’s surface is changing continuously by many processes
Weathering - disintegration & deposition of surface rocks
Physical Weathering (Abrasion)
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Surface Features
Mass Wasting - downward movement of debris due to gravity
Surface Features
Erosion - movement of material due to water or atmosphere
Grand Canyon
Sand Dunes
Surface Features
Geologic - changes caused by plate tectonics
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Geologic Activity
Mt. Everest
Convergent boundary: continental vs. continental
Geologic Activity
Convergent boundary: continental vs. oceanic
Geologic Activity
Mt. St. Helens (1980)
Mt. St. Helens (1982)
Convergent boundary: continental vs. oceanic
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Geologic Activity
Divergent boundary: seafloor spreading (ridge)
Mid-Atlantic Ridge
Continental Drift
Over time, plate motions cause continents to drift apart and come
together (forming super continents, like Pangaea)
Mantle Plumes
Isolated pockets of hot magma in the mantle that give rise to
volcanic island chains and geysers
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Global Hot Spots
Hawaiian Islands
Greenhouse Effect
Without an atmosphere, the global average temperature would
be -17 °C; the greenhouse effect raised that temperature to 17 °C
Greenhouse gases (CO2, CH4) slow the release of IR back into space
Initial CO2 levels were 170,000 times present levels and raised global surface
temperature to 85 °C
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Hydrosphere
The collective mass of water on any world (oceans, rivers, ice caps, clouds)
~ 70% of Earth’s surface covered by water
Climate Regulation
The CO2 Cycle
- Atmospheric CO2 dissolves in rain water, ends up in oceans
- Silicate rocks are eroded and sediments end up in the oceans
- Minerals from rocks mix with CO2 in ocean to form carbonate minerals
- Carbonate minerals sink to ocean floor to make carbonate rock
- Plate tectonics force carbonate rock into mantle along subduction zones
- Carbonate rock melts & CO2 is released through outgassing
Magnetosphere
Serves as protection from the solar wind and other high energy
particles coming from space
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Aurora Borealis
Direct Sunlight
Warmer weather happens when there is a greater amount of
sunlight heating the Earth’s surface.
The amount of heating by sunlight depends on:
- the angle at which the light hits Earth’s surface
- the amount of time the Sun is in the sky
Direct Rays
Oblique Rays
(“Less Direct Rays”)
Direct rays concentrate more light on the same area which heats the
surface more
Direct Sunlight
Earth is not heated uniformly across the surface because it’s round
Rays are most direct near middle of the Earth equator & become less
direct towards the poles.
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Sunlight
If the Earth’s axis were not tilted, the amount of sunlight hitting
each latitude would not change during the course of the year.
No change in temperature means no seasons
Seasons
The tilt of Earth’s axis (23.5°) changes the angle that the sunlight hits
each latitude throughout the year (most direct in the summer).
Seasons
During the summer months the Sun stays above the horizon longer,
thus heating the surface more.
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Tropic Zones (LAT
= 23.5° N/S))
(
The Sun will cross the zenith only for observers within the tropics:
- Tropic of Cancer (Summer Solstice)
- Tropic of Capricorn (Winter Solstice)
Arctic/Antarctic Circles (LAT
= 66.5° N/S))
(
These areas will experience continuous daylight or darkness for 24 hours
Precession
The Earth’
Earth’s axis wobbles in space because the Moon’
Moon’s gravity
pulls on the Earth unequally (26,000 years).
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Effects of Precession
• Polaris will not always be the ‘pole star.’
star.’
• Seasons will occur during different months of the year
The Moon
Geologically inactive
Undetectable magnetic field
No atmosphere
Always see the same side of the Moon
Orbital Period = Rotation Period = 27.322 days
The Moon
Majority of our knowledge comes from 6 Apollo missions.
• Apollo Lunar Surface Experiment Packages (ALSEP)
•Analyzed terrain from orbit.
• Collected 400 kg (880 lb) of lunar samples;
½ are in storage
Total cost: $100 per American, spread over 10 years
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Craters
Formed by high speed impactors (meteoroids)
Mare
Lava filled impact basins that appear as smooth and dark terrain
Few craters found in maria because the
surface is young (3.4 Byrs old)
Mare Tranquillitatis
90% of Earth’s rocks are < 600 million years old
Highlands
Elevated regions formed by the build-up of debris scattered by impact events
Represents the original surface (4.4 Byrs old)
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Water on the Moon?
Why is there no water on the surface?
One “lunar day” is over 650 hours; any liquid water on surface
would have been evaporated shortly after Moon’s formation
H
H
H
H
H
O
O
H
H
H
H
O
H
O
O
Water molecules are dissociated by UV light from Sun
Moon’s low surface gravity can’t prevent H atoms from escaping
Water on the Moon?
LCROSS: discovered water-ice on the floor of Cabeus crater
(Lunar Crater Observation & Sensing Satellite)
Tides
Moon’s gravity is NOT exactly the same at all points on the Earth
Differential gravitational
gravitational force exerted by Moon creates a tidal bulge
Weakest
Strongest
Other influences on tides:
- Earth’s rotation
- Moon’s orbital inclination
- Earth not uniformly covered by water
- Oceanic currents
Sun influences the tides but to a lesser degree than Moon: Farther away
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Lunar Phases
As the Moon orbits Earth our perspective of the light/shadow regions changes
Lunar Phases
Waxing phases
Waning phases
- right side of Moon is lit
- Moon rises/sets after the Sun
- left side of Moon is lit
- Moon rises/sets before the Sun
Eclipses
Light from the Sun casts a shadow in the following way:
Umbra:
Umbra dark, central shadow cast directly behind the object
Penumbra:
Penumbra lighter shadow on the periphery
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Eclipses
Eclipses occur when the following conditions are met:
(1) Moon is in New/Full phase
(2) Moon crosses the ecliptic plane
Eclipses
Total solar eclipse: complete coverage of Sun; only seen where Moon’s
umbra hits surface of Earth
Eclipses
Partial solar eclipse: partial coverage of Sun; seen where Moon’s penumbra
hits Earth’s surface
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Eclipses
Annular: Moon covers central part of Sun because the Moon is
further from Earth so its umbra falls short
Eclipses
Lunar Eclipse – occurs when the Moon passes through Earth’s shadow.
Total: Moon in complete shadow
Partial: Moon moves through part of Earth’s umbral shadow
Eclipses
The Saros Cycle:
Cycle regular cycle of solar eclipses every 18yrs 11.3days
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