Midterm Study Guide 1

Question 1

What are some environmental consequences of a large meteorite impact?

Answer 1

• Giant Earthquake
• Atmospheric Blast
• Fireball
• Global fires
• Tsunami
• Global Darkness
• Temperature Drop
• Acid rain

Question 2

What forms of geologic evidence indicates that a meteorite hit the earth?

Answer 2

• Hole in ground (1991)

• Animal extinction

• Tsunami deposits
• Shocked quartz
• Dissolved CaCO3
  (calcium carbonate, found in rocks)
• Iridium layer (1980): rare at earth’s surface, found in rock that would have been at surface when 
dinosaurs were alive. Iridium is thought to come from dust from meteors disintegrating in 
the atmosphere or collide with earth


Question 3

How did the Cretaceous­Tertiary meteorite change the course of life for the dinosaurs and for mammals?

Answer 3

It caused global extinction for most of life on Earth, including the dinosaurs that had up until the impact ruled Earth. This gave an opportunity for mammals to thrive.
• Caused temperature drop and global darkness that killed non­avian dinosaurs
• Plant life couldn’t perform photosynthesis, loss of energy source.

Question 4

What processes are responsible for generating the heat that differentiated the Earth?

Answer 4

Differentiation is driven by density and heat. Continued gravitational collapse, radioactive decay, and impacts caused increased heating of the planet interior.

Question 5

Explain the sequence of events leading to the formation of our solar system.

Answer 5

• Diffuse, roughly spherical, slowly rotating nebula begins to contract
• A flat, rapidly rotating disk forms with the matter concentrated at the center that will 
become the proto­sun
• The enveloping disk of gas and dust forms grains that collide and clump together into small 
planetesimals
• Terrestrial planets build up by multiple collisions and gravity attraction. Giant outer planets 
grew by gas and accretion.
• The strong thermal and pressure gradient developed by the early sun evaporated the volatile 
elements in the inner planets and condensed them in the colder outer planets

Big Bang —> Quantum Fluctuations —> Inflation —> Afterglow Light Pattern —> Dark Ages —> 1st Stars —> Development of Galaxies, Solar System, Planets, etc. —> Dark Energy Accelerated Expansion

Question 6

How old is the Earth—how do we age date the formation of the earth?

Answer 6

4.567 Ga (billion years) – we know this through Radioactive decay (Uranium decays to Lead) - from meteorite dating and radioactive decay

Question 7

Draw the structure of the earth including thickness of the core, mantle and crust.

Answer 7

• Crust (0­40 km)

• Mantle (40 - 2890 km)

• liquid iron outer core (2890 - ­5150 km) 

• Solid iron inner core (5150 - ­6370 km)

Question 8

What is the source of gases in our atmosphere?

Answer 8

• Degassing of the crust and mantle after planetary differentiation.
• Hydrogen atoms go through nucleosynthesis to form different elements

Question 9

Describe the evidence of the earliest life on earth.

Answer 9

Stromatolite fossils are evidence of the earliest life on earth - the oldest dating more than 3.5 billion years ago.

• Once the earth cooled down, organic molecules concentrated in the sea, formed single cell 
organisms
• Microfossils and Stromatolites (layered accretionary structures found in shallow water)

Question 10

Iridium

Answer 10

High concentrations in Earth’s crust, estimated that a meteor must have collided with Earth
The alvarez hypothesis ­ iridium is uncommon in the earth’s surface but very common in meteorites. A huge layer of iridium is found at the k­t boundary in the earth, 1980.

Question 11

Half­-life

Answer 11

the amount of time necessary for one­ half of the atoms of a particular radioactive
element to decay

Question 12

Volcanic outgassing

Answer 12

a. happens as Earth cools
b. Gases and water on Earth came from “degassing” when gas is pushed out of the Earth during cooling.
c. the release of gases into the atmosphere during volcanic eruptions. A lot of our atmosphere (including water vapor, nitrogen, and argon) came from outgassing.

Question 13

Nucleosynthesis

Answer 13

process of fusion Hydrogen atoms collide to form Helium, elements made by fusion of lighter elements

Question 14

Big bang

Answer 14

a. universe was once extremely hot & dense state which expanded rapidly, this caused the universe to cool and resulted in its present continuously expanding state
b. prevailing cosmological model. Big bang occurred around 13.7 billion years ago, the universe was in an extremely hot and dense state. Created lots of hydrogen

atoms and left afterglow light patterns, leading to dark ages, 1st stars, and
development of galaxies and planets.

Question 15

Hubble

Answer 15

Edwin Hubble at Mt Wilson confirmed the observation that galaxies are moving away from each other with the most distant at the greatest velocity.

Question 16

Doppler effect

Answer 16

• Waves are compressed and decompressed depending on the velocity of the
  traveling object. Higher frequency when the source is moving towards the observer,
  Lower frequency when the source is moving away.
• Stationary police siren = Acoustic wave

Question 17

Accretion

Answer 17

Growth of a massive object by gravitationally attracting more matter, typically
gaseous matter in an accretion disk.

Question 18

Differentiation

Answer 18

a. Driven by Density and Heat
b. Gravitational collapse, radioactive decay of material in earth, impacts
i. Heavier elements sunk to the bottom and melting occurred (high temp and pressure)
c. While the Earth was molten, gravity acted to concentrate more dense material near the center and less dense material nearer the surface. When the Earth solidified
again (except for the liquid outer core) it was left with a layered structure with more dense material like iron and nickel near the center and less dense rocks nearer the surface. As the outer layers cooled and solidified, large cracks developed because of thermal stress, leaving the lithosphere broken up into large blocks or plates.
d. Gasses and water on earth came from Degassing of the crust and mantle during cooling.

Question 19

Mass extinction

Answer 19

Rapid and massive decrease in species

Question 20

Core, mantle, crust

Answer 20

a. Inner core is solid, around 5000­ - 6400 km. Outer core is liquid, around
3000­ - 5000km. Mantle is liquid, 40­ - 3000km, and crust ranges from 0­ - 40km. Oceanic crust is around 5 km.

b. Crust­ very thin
i. Two types of crust.
1. Thin Oceanic Crust (under ocean basins)
a. Rock type: Basalt
2. Thicker Continental Crust (under continents)
a. Rock type: Granite
b. Low density of continental crust allows
it to float on the higher density mantle
below it

c. Mantle
i. Mobile mechanical layer, middle layer
ii. Has different temperatures at different depths
(lowest beneath crust, increases with depth,
highest where mantel is in contact with heat
producing core)
1. Geothermic Gradient: steady increase of
temperature with depth
a. Is responsible for different rock
behaviors that divide the mantel to
two zones
i. Rocks in the upper mantle = cool
and brittle
1. Brittle enough to break =
Earthquakes
ii. Rocks in the lower mantle = hot
and soft (not molten)
2. These two zones of rock are the
Lithosphere (Crust + upper Mantle) and
Asthenosphere (lower part of upper
mantle)

d. Core
i. Hot, center layer
ii. Earth has two cores. Solid center core, an a
liquid outer core.
iii. Composed of 95% Iron, 5% nickel, smidgen
of Sulfur
1. Know due to density and the fact that
many meteorites which are portions of a
planet’s interior, are iron-­nickel
2. The earth’s core is heated because it
contains radioactive materials which
release heat as they break down.
3. Outer core is liquid (2890km­ -
5150km)– because the temperatures
are enough to melt iron and nickel.
LOW VISCOSITY.
4. Inner core is solid (5150­ - 6470km) ­
even though its temperature is higher
than the outer core, because
tremendous pressure produced by
the weight of the overlaying rocks is
strong enough to crowd the atoms
together tightly and prevents a liquid
state.

e. Two big compositional boundaries: MOHO (mantle/crust) and core­-mantle. Two big mechanical boundaries (same composition but behaves differently because of differing temp/pressure): boundary between lithosphere/asthenosphere (called LAB) and boundary between the inner and outer cores.

Question 21

Chicxulub

Answer 21

The crater underneath Yucatan Peninsula in Mexico. Result of the asteroid impact at
K/T boundary. Caused a temperature drop, earthquake, and global darkness

Question 22

Crater

Answer 22

Result of an asteroid impact on Earth, leaving behind an iridium layer

Question 23

Red shift

Answer 23

a. The pattern of emission is shifted towards the red with lower frequency. The stars and galaxies are moving away from each other.
b. Melvin Slipher ­ when a light source moves away from an observer, it has a longer wave length, causing it to “shift” to the red end of the visible spectrum.

Question 24

Crust

Answer 24

b. Crust­ very thin
i. Two types of crust.
1. Thin Oceanic Crust (under ocean basins)
a. Rock type: Basalt
2. Thicker Continental Crust (under continents)
a. Rock type: Granite
b. Low density of continental crust allows
it to float on the higher density mantle
below it

Question 25

Mantle

Answer 25

c. Mantle
i. Mobile mechanical layer, middle layer
ii. Has different temperatures at different depths
(lowest beneath crust, increases with depth,
highest where mantel is in contact with heat
producing core)
1. Geothermic Gradient: steady increase of
temperature with depth
a. Is responsible for different rock
behaviors that divide the mantel to
two zones
i. Rocks in the upper mantle = cool
and brittle
1. Brittle enough to break =
Earthquakes
ii. Rocks in the lower mantle = hot
and soft (not molten)
2. These two zones of rock are the
Lithosphere (Crust + upper Mantle) and
Asthenosphere (lower part of upper
mantle)

Question 26

Core

Answer 26

d. Core
i. Hot, center layer
ii. Earth has two cores. Solid center core, an a
liquid outer core.
iii. Composed of 95% Iron, 5% nickel, smidgen
of Sulfur
1. Know due to density and the fact that
many meteorites which are portions of a
planet’s interior, are iron-­nickel
2. The earth’s core is heated because it
contains radioactive materials which
release heat as they break down.
3. Outer core is liquid (2890km­ -
5150km)– because the temperatures
are enough to melt iron and nickel.
LOW VISCOSITY.
4. Inner core is solid (5150­ - 6470km) ­
even though its temperature is higher
than the outer core, because
tremendous pressure produced by
the weight of the overlaying rocks is
strong enough to crowd the atoms
together tightly and prevents a liquid
state.

Question 27

Inner Core

Answer 27

a. Inner core is solid, around 5000­ - 6400 km. Outer core is liquid, around
3000­ - 5000km. Mantle is liquid, 40­ - 3000km, and crust ranges from 0­ - 40km. Oceanic crust is around 5 km.

Question 28

Compositional Boundaries

Answer 28

e. Two big compositional boundaries: MOHO (mantle/crust) and core­-mantle. Two big mechanical boundaries (same composition but behaves differently because of differing temp/pressure): boundary between lithosphere/asthenosphere (called LAB) and boundary between the inner and outer cores.