Week 1 Course Notes: Section 1.0 - 2.0

Question 1

Explain the “Unifying Principle of Geology”

Answer 1

This term refers to how Plate Tectonics as a theory has been able to effectively explain the origin of Earth’s geological features. It is able to tie together apparently unrelated geologic events into a single concept.

Question 2

What is the Principle of Plate Tectonics?

Answer 2

The theory that the Earth’s surface is divided into a series of rigid lithospheric plates that over time move on top of the plastic asthenosphere driven by convection cells in the underlying mantle.

Question 3

What two supercontinents were proposed that Pangea consisted of?

Answer 3

Gondwanaland - southern hemisphere continents
Laurasia - northern hemisphere continents

Question 4

List seven key evidences that support Plate Tectonics

Answer 4

• Fit of continents
• Similarity of rock sequences/mountain ranges
• Glacial evidence
• Fossil evidence
• Paleomagnetism and polar wandering
• Ocean ridges and trenches
• Magnetic reversals

Question 5

Explain the theory behind a mantle convection cell?

Answer 5

A hypothesis proposed by Hess where the ocean floor separates at oceanic ridges and subducts at ocean trenches and is driven by hot magma extruding at the ridges and cold crust subducting at trenches.

Question 6

What does the Vine-Matthews-Morely hypothesis propose?

Answer 6

That the magnetic pattern (normal and reverse polarity) of rocks on one side of an oceanic ridge is identical to the pattern on the other side, showing that the sea floor is spreading along oceanic ridges.

Question 7

Describe the Crust of the Earth

Answer 7

Thin and rigid

• Oceanic crust: 5 - 10 km thick and consists of dense mafic volcanic basalt
• Continental crust: 20 - 40 km thick and consists mostly of the less-dense felsic rock granite

Question 8

Describe the Mantle of the Earth

Answer 8

~2900 km thick and varies from rigid to plastic
- consists of ultramafic rocks (high temp and pressure)

Question 9

Describe the Core of the Earth

Answer 9

Sphere of 3470 km radius

• consists mostly of iron and nickel
• outer core is molten
• inner core is solid

Question 10

What is the Lithosphere?

Answer 10

Consists of crust and uppermost mantle
- is rigid and ~70 km thick beneath oceans and ~125 km thick beneath continents

Question 11

What is the Asthenosphere?

Answer 11

Consists of the upper mantle below the lithosphere
- plastic or semi-molten
- extends to ~ 350 km in depth

Question 12

At what rate do plates move past each other?

Answer 12

1 to 10 cm/year

Question 13

What are the 3 main types of plate boundaries?

Answer 13

• Divergent
• Convergent
• Transform

Question 14

Describe Divergent Plate Boundaries

Answer 14

Plates moving away from each other

• new crust made at rift
• Ocean-ocean boundary creates mid-oceanic ridge
• Continent-continent boundary creates a rift valley

Question 15

Describe Convergent Plate Boundaries

Answer 15

Plates moving toward each other

• Ocean-ocean boundary means one plate is subducted under the other
• Ocean-continent boundary means oceanic crust subducted under less dense continent
• Continent-continent boundary means collisional mountain belt formed

Question 16

Describe Transform Plate Boundaries

Answer 16

Plates move past each other horizontally in opposite directions

• common transform boundaries connect two divergent boundaries due to irregular movements

Question 17

What are Mantle Plumes?

Answer 17

Stationary regions which have a rising column of hot plastic magma originating deep within mantle. Plumes erupt large amounts of magma at surface which form volcanoes at locations called Hot Spots.