Lecture 15

Question 1

Theory

Answer 1

A coherent group of general propositions used as principles of explanation for a class of phenomena.

Question 2

Hypothesis

Answer 2

A proposition proposed as an explanation for the occurrence of some specified group of phenomena.

Question 3

Law

Answer 3

Well-established propositions that are regarded as reporting matters of fact.

Question 4

Plate Tectonics

Answer 4

A unified theory of the solid earth that explains many of the puzzles that we identified in previous lectures.

Question 5

Continental Drift Hypothesis

Answer 5

All of the present-day continents were once part of a single super-continent called Pangaea.

Question 6

Evidence of Continental Drift Hypothesis

Answer 6

1. The close fit between the coastlines of Africa and South America.
2. Glacial features from essentially the same time period appear in South America, Africa, India, and Australia.
3. Fossils of identical plants and animals found on all continents.
4. Large-scale geological features on different continents matched when the continents were brought together.
5. Fossils found in some places do not match current climates.

Question 7

How did Wegener construct Pangaea?

Answer 7

Used the location of specific rock types to determine the distribution of climate zones in the geologic past.

Question 8

What was the major weakness of the Continental Drift Hypothesis?

Answer 8

Major weakness was the lack of a viable mechanism for the “drifting continents.”

Question 9

Plate Tectonics replaces Continental Drift

Answer 9

Convection currents which bring hot magma up from the deep mantle and cooler rock downward could drive continental motion.

Question 10

Sea-floor spreading

Answer 10

Magma comes to ocean floor at ridges; Magma erupts as sub-sea volcanoes and produces new basaltic crust.

Question 11

What did the 1968 deep sea drilling project reveal?

Answer 11

Ocean floor is geologically young (~180 million years)

Question 12

Oceanic Crust

Answer 12

Compose of basalt; relatively thin

Question 13

Continental Crust

Answer 13

Composed of granite; relatively thick

Question 14

Theory of plates

Answer 14

Sea-floor spreading and continental drift combined. The Earth’s outer shell (lithosphere) consists of rigid plates. The plates slide on the softer asthenosphere. As the plates move they carry continents and ocean floor. When continents and ocean floor converge, a deep valley is formed and ocean floor “subducts” beneath continents.

Question 15

The types of Plate Motion

Answer 15

Divergent, Convergent, Transform

Question 16

Divergent plate boundaries

Answer 16

Lithospheric plates which move away from each other.

Question 17

Smokers

Answer 17

Provide unique enviroments for microbes that are able to flourish at high temperatures. It is thought that they may have been the cite of the initial evolution of living organisms.

Question 18

Convergent Plate Boundaries

Answer 18

The surface area of the Earth is finite. If new crustal material is being created at divergent boundaries, there must be convergent boundaries where crustal material is consumed.

Question 19

Subduction

Answer 19

When the oceanic lithosphere arrives at the edge of a continent, it sinks into the asthenosphere. The area where this sinking occurs is called a subduction zone.

Question 20

Ocean-Continent Convergent Plate Boundary

Answer 20

The oceanic lithospheric plate is pushed toward and beneath the continental plate. The subduction of the oceanic material can produce magma which can cause volcanic activity and new mountain formation.

Question 21

Ocean-Ocean plate convergence

Answer 21

One plate is subducted under the other, forming a trench. Volcanic activity, produced by the partial melting of the descending plate and/or the overlying oceanic lithosphere, causes a pile up of lava on the ocean floor which eventually rises above sea level to form an island volcano.

Question 22

Continent-Continent Convergent Plate Boundaries

Answer 22

When 2 continents meet, neither is subducted. Instead the crust buckles and is pushed upwards or sideways.

Question 23

Transform Plate Boundary

Answer 23

Plates slide past each other.