planet earth. how old is the earth? :10 0 of 116 1.140 million years 2.500 million years 3.1 billion...
TRANSCRIPT
Planet Earth
How old is the Earth?
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1. 140 million years
2. 500 million years
3. 1 billion years
4. 4.6 billion years
5. 13 billion years
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The Early History of the Earth
Earth formed 4.6 billion years ago from the inner solar nebula.
Four main stages of evolution:
What is “differentiation”?
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1. The mixing of substances.2. Lighter substances sinking to
the bottom, while heavier substances rise to the top.
3. Heavier substances sinking to the bottom, while lighter substances rise to the top.
4. The chemical change of substances near the surface of a planet due to chemical reactions with the atmosphere.
5. The chemical change of substances near the core of a planet induced by great heat.
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The Early History of the Earth
Earth formed 4.6 billion years ago from the inner solar nebula.
Four main stages of evolution:
Two sources of heat in Earth’s interior:
• Potential energy of infalling material
• Decay of radioactive material
Most traces of bombardment (impact craters) now destroyed
by later geological activity
What killed the dinosaurs (according to the most
widely accepted theory)?
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1. Global climate change caused by variations in the sun’s energy output.
2. Global climate change caused by a massive meteorite/comet impact.
3. A reptile dysfunction.4. A nearby stellar explosion
(supernova / gamma-ray burst).
5. Nothing. They still exist (see, e.g., Jurassic Park)!
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Meteorite Impacts on EarthOver 150 impact craters found on Earth.
Most famous example:
Barringer Crater near Flagstaff, AZ:
Impact Craters on EarthBarringer Crater: ~ 1.2 km diameter; 200 m deep
Formed ~ 50,000 years ago by a meteorite of ~ 80 – 100 m diameter
The Chicxulub Crater
This impact may have caused major climate
change, leading to the extinction of many species, including dinosaurs
.
Much larger impact features exist on Earth:
Impact of a large body (comet nucleus?) formed a crater ~ 180 – 300 km in diameter in the Yucatán
peninsula, ~ 65 million years ago:
Seismic waves are bent or bounce off transitions
between different materials or different
densities or temperatures.
Earth’s InteriorDirect exploration of Earth’s interior (e.g.
drilling) is impossible.
Earth’s interior can be explored through
seismology:
Earth quakes produce
seismic waves.
If you are standing next to railroad tracks and you don’t see or hear a train, you can tell if there’s a train approaching by
putting your ear on the tracks. This works because …
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1. your visual abilities improves when you block one of your ears.
2. sound waves travel more rapidly along the tracks than through the air.
3. Sound waves get less absorbed when traveling along the tracks than through the air.
4. All of the above.5. 2. and 3.
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Earth’s Interior (II)
Earth’s interior gets hotter towards the center.
Earth’s core is as hot as the sun’s surface;
metals are liquid near the core.
Basic structure:
Solid crust (light [Si-based] materials)
Solid mantle (light elements, iron-poor)
Liquid core (iron-rich)
Solid inner core (iron-rich)
Earth’s Magnetic Field
Convective motions and rotation of the core generate a
dipole magnetic field
Earth’s core consists mostly of iron + nickel
(materials that magnets are made
out of)
The Role of Earth’s Magnetic FieldEarth’s magnetic field protects Earth from high-energy
particles coming from the sun (solar wind).
Surface of first interaction of solar wind with Earth’s magnetic field =
Bow shock
Region where Earth’s magnetic field dominates = magnetosphere
Some high-energy particles leak through the magnetic field and produce a belt of high-energy particles around Earth: The Van Allen belts
Which phenomenon is caused by the interaction of energetic particles from the
sun with Earth’s magnetosphere?
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1. Northern lights (aurora borealis).
2. Sun spots.
3. Prominences.
4. Hurricanes.
5. Earthquakes.
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The Aurora (Polar Light)
As high-energy particles leak into the lower magnetosphere, they excite molecules near the Earth’s magnetic poles, causing the
Aurora
Tectonic PlatesEarth’s crust is composed of several distinct tectonic plates, which are
in constant motion with respect to each other → Plate tectonics
Tectonic Plates (II)
Evidence for plate tectonics can be found on the ocean floor
… and in geologically active regions all around the Pacific
Geological activity around the Pacific
Volcanism: Mt. St. Helen
Earthquakes: Kobe (Japan)
Volcanism: Pinatubo (Philippines)
Earthquakes: San Francisco
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1) the African and the Indian-Australian Plates.
2) the Indian-Australian and Eurasian Plates.
3) the African and the Arabian Plates.
4) the Arabian and the Indian-Australian Plates.
5) the African and Antarctic Plates.
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Plate TectonicsTectonic plates move with respect to each other.
Where plates move toward each other, plates can be
pushed upward and downward → formation of mountain
ranges, some with volcanic activity, earthquakes
Where plates move away from each other, molten
lava can rise up from below → volcanic activity
Active Zones Resulting from Plate Tectonics
The interaction between the Pacific and the North American Plates is responsible for the formation of
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1) the Hawaiian Islands.
2) the Alps.
3) the Rocky Mountains.
4) the Andes.
5) the Appalachian Mountains.
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Volcanism on Earth (I)
Volcanism on Earth is commonly found along subduction zones (e.g., Rocky Mountains).
This type of volcanism is not found on Venus or Mars.
Subduction Zones
Example: Stromboli (Sicily, Italy, 1998)
Hawaii is also very volcanically active. Is this also because Hawaii is located at a plate boundary?
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1) Yes, it is located at the boundary of the Pacific plate.
2) Yes, it is located at the boundary of the North American plate.
3) Yes, it is located at the boundary of the Eurasian plate.
4) No. This must be a different kind of volcanic activity.
5) No. Hawaii is not volcanically active.
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Shield Volcanoes
Found above hot spots:
Fluid magma chamber, from
which lava erupts repeatedly through
surface layers above.
All volcanoes on Venus and Mars are shield volcanoes
Volcanism on Earth (II)
Shield Volcanoes (II)Tectonic plates moving over hot spots producing
shield volcanoes → Chains of volcanoes
Example: The Hawaiian Islands
Earth’s Tectonic History
Earth’s Tectonic History (II)
History of Geological Activity
Surface formations visible today have emerged only very recently compared to the age of Earth.
Guess: How thick is the Earth’s breathable atmosphere (beyond which you would need oxygen masks to breathe), compared to the Earth’s radius?
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1) 1/24,000 Earth radius.
2) 1/800 Earth radius.
3) 1/15 Earth radius.
4) 1 Earth radius.
5) 10 Earth radii.
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Earth’s Atmosphere
Only about 1/800 of the
Earth’s radius!
Which is the most common gas in Earth’s atmosphere?
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1) Oxygen
2) Nitrogen
3) Carbon dioxide
4) Methane
5) Water vapor
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The Atmosphere
Earth had a primeval
atmosphere from
remaining gasses
captured during
formation of Earth
Do you think that the Earth’s atmosphere is still very similar to what it was about 4 billion years ago?
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1) Yes
2) No
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The Atmosphere
Atmospheric composition severely altered (→ secondary atmosphere) through a combination of several processes:
Earth had a primeval
atmosphere from
remaining gasses
captured during
formation of Earth
Sources of Atmospheric Gas• Outgassing: Release of gasses bound in compounds in
the Earth’s interior through volcanic activity
• Later bombardment with icy meteoroids and comets
Loss of Atmospheric Gas• Chemical reactions in the oceans
• Energetic radiation from space (in particular, UV)
Which of these processes might be the main reason that Mercury has almost no atmosphere?
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1. Thermal Escape
2. Stripping by energetic radiation from space
3. Condensation
4. Chemical reactions
5. Ejection by impacts
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Which of these forms of radiation from space can reach the Earth unabsorbed?
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1) Radio waves.
2) Infrared light.
3) Ultraviolet light.
4) X-rays.
5) Gamma-rays.
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The Electromagnetic Spectrum
Need satellites to observe
Wavelength
Frequency
High flying air planes or satellites
The Interactions between Light and Molecules
X-rays
1) Splitting up molecules into atoms:
Nitrogen (N2) / Oxygen (O2)
2) Ionizing (kicking electrons out of) atoms or molecules
The Interactions between Light and Molecules
Ultraviolet
Splitting up molecules, in particular, Ozone:
Ozone (O3)Oxygen (O2)
Why is the totally eclipsed moon visible at all (in a faint red glow)?
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1) Because it is still glowing from the intense light it received during full moon before the eclipse.
2) Because it is illuminated by sunlight reflected off other terrestrial planets.
3) Because it is illuminated by sunlight scattered within the Earth’s atmosphere.
4) Because it is very shy during the eclipse and turns red when you are looking at it.
5) None of the above: The totally eclipsed moon is completely black.
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The Interactions between Light and Molecules
Penetrates through the atmosphere mostly unabsorbed,
but can get scattered:
Visible Light
This is why the sun appears red at
sunrise and sunset; and why the sky is
blue (if it’s not cloudy)
The Interactions between Light and Molecules
Carbon dioxide (CO2) /
Water vapor (H2O) /
any other asymmetric molecules (greenhouse
gases)
Infrared
Causes asymmetric molecules to rotate
This is the essential step of the
Greenhouse Effect!
We know that UV and X-ray radiation from space is heating the atmosphere. Thus, do you expect that the atmosphere becomes
hotter or colder with height, very high above the ground?
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1) Hotter with increasing height.
2) No temperature change.
3) Colder with increasing height.
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The Temperature Structure of Earth’s Atmosphere
Exosphere: Heated by UV and X-rays from space
Thermosphere: Heated by X-rays from space
Stratosphere: Heated by UV radiation from space
Troposphere: Heated by greenhouse effect
Ozone Layer
Atmosphere gets colder at larger distance from heat sources.
Top of Ozone Layer
Temperature
Alti
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