Lec5: Geological History of Antarctica

Question 1

Give the 5 measurements of timescale in order.

Answer 1

Eons, Eras, Periods, Epochs, Stages

Question 2

Describe the “double-crusted” structure of the Earth’s crust.

Answer 2

Less dense continental crust floats on the more dense oceanic crust.

Question 3

Which layer of the earth contains most internal heat?

Answer 3

Mantle.

Question 4

Describe the two layers of the Core, and which creates the Earth’s magnetic field.

Answer 4

1. Outer layer = liquid nickel-iron alloy (magnetic field)

2. Inner layer = solid iron

Question 5

How many major crustal plates does the Earth have and what are the three major layers in a crustal plate?

Answer 5

9.

Crust on solid upper mantle on liquid lower mantle.

Question 6

What is a “hot spot”?

Answer 6

Region of mantle upwelling.

Question 7

What are the three types of plate boundaries, and give an example of each?

Answer 7

1. Divergent boundary/Spreading center - Mid-Atlantic Ridge between North America and Europe
2. Convergent boundary/Subduction zone - Mariana Trench, or Collision Boundary = Himalayas between Indo-Australian and Eurasian plates
3. Transform boundary - NZ Alpine Fault (Southern Alps) betweeen Indo-Australian and Pacific plates

Question 8

Describe a divergent boundary.

Answer 8

Plates move away from each other. Erupting magma rises up and cools, forming new crust.

Question 9

What causes sea-floor spreading?

Answer 9

In divergent boundaries, non-erupting magma moves under crust and causes sea to expand.

Question 10

What is a convergent boundary, and what happens when the “convergence” fails?

Answer 10

Thin, dense plate slides under thick, less dense plate.

Otherwise, they buckle up and form mountain chains = collision boundary.

Question 11

What is a transform boundary?

Answer 11

Continental plates slide past each other.

Question 12

What is the largest, ice-free region in Antarctica?

Answer 12

McMurdo dry valleys.

Question 13

Where are the McMurdo dry valleys located?

Answer 13

Victoria land, West side of McMurdo Sounds.

Question 14

What are the three valleys of the McMurdo’s, in order form North to South.

Answer 14

Victoria, Wright, Taylor.

Question 15

What sort of organisms can one expect to find in the McMurdo Dry Valleys?

Answer 15

No tracheophytes or vertebrates, only moss, lichens and microorganisms.

Question 16

What process formed the McMurdo Dry Valleys, and what process caused them to deepen (during which era)?

Answer 16

Formed by river erosion, and deepened by glaciation during the Miocene.

Question 17

What are the two main reasons that the McMurdo Dry Valleys are so dry?

Answer 17

1. Katabatic winds are funnelled through valleys –> flow downwards, thus increasing temperature and therefore heat (adiabatic heating), thus increasing surface temp. This causes sublimation of snow and ice.
2. Valleys are in a Precipitation Shadow: Cold southern winds are blocked by mountain range

Question 18

How are soil polygons formed, where are they found, and what is their structure analogous to?

Answer 18

Through repeated thawing and freezing of groundwater near surface (McMurdo Dry Valleys). Analogous to basketball-textured terrain on Mars.

Question 19

Describe the salt and nitrate concentration in soil in the Dry Valleys.

Answer 19

High salt = lots of metals and salts

Low Nitrate = mainly through atmospheric precipitation

Question 20

What are ventifacts and where are they found?

Answer 20

Wind-carved rock patterns found in Dry Valleys.

Question 21

What is the Labyrinth and where is it located?

Answer 21

Series of canyons through the Ferrar Dolerite at the head of the Wright Valley.

Question 22

Where do the canyons of the Labyrinth emerge from?

Answer 22

EAIS.

Question 23

What could not possibly have formed the Labyrinth, and so what do the scientists instead attribute it to? What did this mean for global ocean temperatures during which era?

Answer 23

Erosion caused by meltwater alone does not account for the great volume of water that would have been required to carve out the Labyrinth.
Suspect episodic drainage of subglacial lakes in EAIS. Spillover into Southern Ocean may explain fluctuations in ocean temps during the middle Miocene.

Question 24

In what time period was the Beacon sanstone/supergroup formed and what do they contribute to?

Answer 24

Devonian + Jurassic = TA mountains

Question 25

What are the names for the dark dolerites running parallel to and crossing through the white Beacon Sandstone respectively? In which time period were these formed?

Answer 25

Conspicuous spills = parallel
Dykes = crossing through

Late Jurassic.