Quiz 4

Question 1

Nicolaus Steno

Answer 1

Danish physician, “Godfather of Stratigraphy”, created stratigraphic principles

Question 2

Principle of Superposition

Answer 2

whatever on top is younger than what’s beneath it

Question 3

Principle of Lateral Continuity

Answer 3

beds are deposited uniformly in lateral directions unless something is blocking them

Question 4

Unconformities

Answer 4

Gaps in the rock record (missing periods of time)

Question 5

What can cause unconformities?

Answer 5

Erosion (happening at a faster rate than deposition)
No deposition
Large changes in condition (like switching from an igneous environment to uplifting a sedimentary environment)

Question 6

Types of unconformities

Answer 6

Disconformities
Angular unconformity
Nonconformity

Question 7

Disconformity

Answer 7

Happens from missing deposition or erosion

Question 8

Angular unconformity

Answer 8

Rocks are deformed (then eroded)

Question 9

Nonconformity

Answer 9

Sedimentary rocks are deposited on top of igneous or metamorphic rocks

Question 10

Faunal succession

Answer 10

The stratigraphic ordering of fossils

Question 11

Desirable features of index fossils

Answer 11

Very common (chances of being buried are good)
Hard parts (good chances of fossilization)
Wide geographic range (correlation over a wide region is possible)
Lived in/deposited in different environments
Distinctive features (can be recognized from similar forms)
Short geological duration (few million years at most; provides a more specific age range)

Question 12

Biostratigraphic correlation

Answer 12

Associating fossils and layerings of fossils to different time periods (and correlating that with different rock formations)
Good for determining a global relative time scale, but numerical/absolute time is still unresolved

Question 13

Geochronology

Answer 13

Another name for numerical dating

Question 14

Isotopes

Answer 14

A special chemical element having a different number of neutrons (but the same number of protons)

Question 15

Stable isotopes

Answer 15

Non-radioactive isotopes that occur naturally

Question 16

Radiogenic isotopes

Answer 16

Isotope that radioactively decays from an “unstable” parent to a “stable” daughter isotope

Question 17

Natural uranium

Answer 17

High concentration of Uranium-238

Question 18

Low-enriched, highly-enriched (and depleted, as a result of the enrichment process) deal with which isotope of uranium?

Answer 18

Uranium-235 (which has a shorter half-life than Uranium-238)

Question 19

Low enriched uranium

Answer 19

Most commercial reactor fuel uses it

Question 20

Highly enriched uranium

Answer 20

Used in naval propulsion reactors, nuclear weapons, and some research reactors

Question 21

Alpha decay

Answer 21

Process where an unstable nucleus changes to another element by shooting out a particle of two protons and two neutrons

Question 22

Beta decay

Answer 22

Decay in which a proton in a nucleus is converted to a neutron (after an electron is removed)

Question 23

Isotopic dating

Answer 23

Gives the time a mineral cooled below its “closure temperature”
Cooling of magma or lava to solid in igneous rock
In metamorphic rock: dropping below closure temperature

Question 24

Oldest crystal and rocks dated

Answer 24

Zircon crystals in Australia: 4.3 billion years
Oldest rock in Canada: 4.03 billion years

Question 25

Radon

Answer 25

Produced by the radioactive decay of Ur and Th (one part of the long decay chain) Emits alpha particles that damage human tissues

Question 26

Radiocarbon dating (name what it is, what it uses, and what that element has a half life of)

Answer 26

Uses carbon-14 (living organisms keep it in equilibrium with the atmosphere until their death, when carbon-14 starts to decay to nitrogen-14) Estimates the age of organic materials up until 62k years ago (as it has a half-life of 5730 years)

Question 27

Other numerical dating techniques

Answer 27

Growth rings (trees and shells) Rhythmic layering (annual layers in sediments or ice)

Question 28

Evidence of plate tectonics (7 bits)

Answer 28

1. Atlantic coastline/Gondwanaland 2. Continental drift 3. Fossil record (fossils spread across different continents that were once suggested) 4. Geologic similarities 5. Magnetism, magnetic reversals, magnetic stripes on the seafloor 6. Topography of the Atlantic 7. Seafloor spreading

Question 29

Eduard Suess

Answer 29

Suggested the continents were once together as a supercontinent called "Gondwanaland" (1890s)

Question 30

Alfred Wegener

Answer 30

Idea of continental drift in 1915

Question 31

Other explanations for fossil record evidence

Answer 31

Rafting (across ocean) Landbridges/Isthmian links Island stepping stones Wind currents

Question 32

South America and Africa share what type of rock

Answer 32

Flood basalts, formed from a hotspot

Question 33

Glacial striations

Answer 33

Marks where a glacier scratched bedrock

Question 34

Magnetic stripes

Answer 34

Symmetric magnetic signals across what we know to be the mid-ocean ridge

Question 35

Marie Tharp

Answer 35

Made maps showing the topography of the ocean; ridges and really deep trenches that pointed to plate locations

Question 36

Proposed (the accepted idea) of plate tectonics

Answer 36

1965, J. Tuzo Wilson

Question 37

Proposed the idea of seafloor spreading

Answer 37

1962: Harry Hess and Robert S. Dietz Other folks later confirmed it in 1963

Question 38

Divergent plates

Answer 38

Plates moving apart creates new lithosphere; occurs at mid-ocean ridges Forms volcanoes Shallower earthquakes

Question 39

Convergent

Answer 39

Plates moving together causes them to collide, then pull one under the other, causing that plate to meet the mantle and be recycled Forms volcanoes Deeper earthquakes

Question 40

Transform plates

Answer 40

Plates slide horizontally past each other, often happening in between divergent or convergent boundaries No active volcano formation Shallower earthquakes

Question 41

Plate movement rate (at the outlier)

Answer 41

~15 - ~100 mm/year Nazca plate: ~150 mm/year

Question 42

Distance India moved (which has led to the formation of the Himalaya mountains, after the breakup of Pangaea)

Answer 42

3,300 km

Question 43

T/F: plate tectonics has occurred for all of Earth's history

Answer 43

False: only 85% of modern continental crust was present by the end of the Archean period

Question 44

What causes plates to move?

Answer 44

Thought to be the convection of the mantle

Question 45

Considerations to be made when installing a GPS station:

Answer 45

Attached to bedrock/hard rock (not susceptible to weathering/erosion beneath) Be aware of biology around the station (which could lead to a noisy signal) Put it in an area that's interesting for scientific questions

Question 46

Some things that GPS motion can help us understand

Answer 46

Plate motion, underground magma, changing glaciers and snow depth, compacting ground, changing amount of groundwater, size of lakes and reservoirs, amount of soil moisture, amount of water in the atmosphere, vegetation growth, amount of ash in atmosphere, sea level

Question 47

If stations are moving in different directions, then to get the total displacement along the fault, you need to _________ their rates together

Answer 47

add