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Ess 101 Exam 1 Questions With Correct Detailed Answers .
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Ess 101 Exam 1 Questions With Correct Detailed Answers .
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Ess 101 Exam 1 Questions With CorrectDetailed Answers .
nebular hypothesis - ANSWER- 1. supernova and formation of primordial dust cloud
2. condensation of primordial dust forms disk shaped nebular cloud rotating counter-
clockwise.
3. proto sun and planets begin to form
4. accretion of planetesimals and differentiation of planets and moons (4-6 billion years
ago).
5. existing solar system takes shape.
Evidence of nebular hypotheses - ANSWER- 1. Planets and moons revolve in a
counter-clockwise direction (not random)
2. almost all planets and moons rotate on their axis in a counter-clockwise direction.
3. planetary orbits are aligned along the suns equatorial plane (not randomly organized)
4. observations from Hubble telescope and radio astronomy indicate that other
planetary systems are forming from condensed nebular dust.
Terrestrial Planets - ANSWER- Close to the sun, dense, small/rocky, silicate minerals,
metallic cores
Twelve earths would fit across the diameter of Jupiter.
Jovian Planets - ANSWER- Far from the sun, low density, large, gaseous (hydrogen,
methane)
Why does the earth and terrestrial planets have so little molecular hydrogen comprising
their respective atmosphere, yet the primordial dust cloud was mostly comprised of
hydrogen gas? - ANSWER- Hydrogen gas and helium gas escapes to space when put
in our atmosphere.
Jupiter, saturn, and neptune maintain molecular hydrogen gas in the atmosphere
because they have high density.
Differentiated Earth - ANSWER- 1. Iron Nickel Core (outer core liquid)
(inner core solid)
2. Fe-Mg silicate mantle
3. Fe-Mg-Al Silicate Crust (Ocean and Continental)
4. Oceans
5. atmosphere
How is the earth compositionally zoned? - ANSWER- Along a density gradient
,How did the earth become compositionally zoned? - ANSWER- 1. Accretion of
planetesimals
2. initial heating due to kinetic energy of colliding planetesimals and compressional
heating.
3. additional heating from radioactive decay.
4. iron catastrophe: melting temp of iron reached and dense iron nickel sink to core and
lighter materials are displaced outwards (including silicate rock of mantle and crust,
ocean waters and atmospheric gases)
5. earth becomes compositionally zoned based on density (densest iron nickel in core-
least dense materials comprise the atmosphere) 500 mil yrs after the initial accretion
process.
6. convective overturn in asthenosphere, mantle and outer core still occur today.
Why did the earth heat up and then rapidly cool during the differentiation process? -
ANSWER- When earth was solid-heat gain was greater than the heat lost to space. This
means that the internal temperature rises until it exceeded the melting temp of oxygen
and nitrogen until exceeded iron nickel catastrophe. Earth is completely molten and
then compositionally zoned.
When earth was liquid- convection-hot gas rises , after it became molten, the earth
rapidly cooled off and solidified.
Why does earth possess little evidence of its early accretion history? - ANSWER-
Because of weathering, plate tectonics, moon has no atmosphere and biosphere.
Emissions from degassing of the earth during its differentiation. - ANSWER- h2o, co2,
h2, he, n2
Where did molecular H and He escape to? - ANSWER- space
When did oxygenation of the atmosphere occur? - ANSWER- later following evolution of
marine algae and plants that use photosynthesis to convert co2 to o2 as a part of their
life processes.
What layers of the earth can be directly observed? - ANSWER- crust and uppermost
mantle.
Evidence of initial composition of the solid earth based on meteorite studies. There are
two major classes of meteorites that dominate collected samples. Carbon based
meteorites are much rarer, but indicate that the prescursor of life was present early on. -
ANSWER- 1. Metallic meteorites (iron nickel density 9.0-10 gm/cm3)
2. chondritic meteorites: Fe-Mg silicate, rocky, density is 3.0-3.3)
3. carbonaceous chondrites (rare)
What is earths average density? - ANSWER- 5.5 g/cm3
, How can average density of earth be inferred? - ANSWER- Based on gravitational
properties and its effect on known masses such as orbiting satellites.
Density of earths crust? - ANSWER- 2.6-3 g/cm3
density of uppermost mantle? - ANSWER- 3.0-3.3 g/cm3
Based on the density information, what can you infer about the density of the lower
mantle and the earths core? - ANSWER- Density must be higher than the average.
What does the presence of the Earth's magnetic field provide evidence for? - ANSWER-
Earth is likely to possess a metallic core and that a component of this core must be
liquid and convecting around the solid metallic portion of the core.
Seismic waves - ANSWER- s and p waves
P waves - ANSWER- Compression waves, velocity: 6-7 km/sec within lithosphere,
propagate through all phases of matter.
S waves - ANSWER- Shear waves, 3-4 km/sec, only propagate through solid phases of
matter, not liquids or gases, require rigid substance (solid) to propagate.
Seismic waves refract because - ANSWER- because of velocity changes related to
density changes within the earth. seismic wave accelerate with increasing density.
P wave shadow zone - ANSWER- bagel shaped, exist between 105-140 degrees from
the epicenter due to refraction at outer core mantle boundary.
no p or s waves.
s wave shadow zone - ANSWER- only one large shadow zone at an angle greater than
105 degrees of the epicenter. due to refraction at outer core mantle boundary and
because s waves are absorbed by the liquid outer core.
When does seismic wave velocity decrease? - ANSWER- at depth of 100-350 km and
at the mantle-core boundary. (low velocity zone)
When are s waves absorbed? - ANSWER- only at the mantle-core boundary.
What does the s wave being absorbed only at the mantle core boundary tell you about
the physical property of the upper mantle? - ANSWER- It is partially melted.
lithosphere - ANSWER- continental, ocean crust, and uppermost solid mantle
Asthenosphere - ANSWER- upper ductile mantle
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