Lecture 2 - The Deep

Question 0

What did he suggest about the continents of the Earth?

Answer 0

That a very long time ago all land had been joined together in one huge continent called Pangea

Question 1

Alfred Wegner (1880-1930) used what as an analogue for how continents could float

Answer 1

Icebergs

Question 2

What evidence did Wegner use to support his theory?

Answer 2

Faunal and floral evidence

Question 3

What 4 examples of faunal and floral evidence was there to support Wegners theory?

Answer 3

Mesosaurus
Glossoptreus
Lystrosaurus
Cynognathus

Question 4

What other evidence did Wegner have?

Answer 4

• The continents appeared to match up

- Distribution of fossils across southern continents suggested prior connectivity

Question 5

What did Dr. Chamberlin, University of Chi-Town wassup, comment on Wegners theory?

Answer 5

‘Wegners hypothesis takes considerable liberty with our globe, and is less…tied down by awkward ugly facts than most of its rival theories.’

Question 6

During the Cold War (1945-1989) oceans became a battlefield, so what was needed?

Answer 6

Accurate underwater charts

Question 7

The echo sounder resulted from anti-submarine warfare, what did the short and long delay mean?

Answer 7

Short Delay = shallower depth

Long delay = greater depth

Question 8

What was revealed by echo-sounding across the Pacific Ocean?

Answer 8

A rugged sea floor topography

Question 9

Seismic surveys showed more than just the sea floor, by penetrating the ocean floor what other geological layers were revealed?

Answer 9

• Sediment (1km)

- Denser oceanic crust, made from basalt, an igneous rock (7km)

Question 10

When was the first detailed map of ocean floor topography revealed?

Answer 10

1956

Question 11

Measuring the strength of the magnetic field in the rocks of the sea floor showed what?

Answer 11

They ran parallel to ocean ridges

Question 12

What is magnetite?

Answer 12

Motonori Matuyama realised iron rich rocks can be magnetised, but magnetism differs from place to place

Question 13

Where else do magnetic fields emanate?

Answer 13

The surface of the sun, and the aurora borealis

Question 14

What doe the Earths magnetic field shield is from?

Answer 14

A stream of ionised gases (the solar wind) that blows outwards from the sun at 400km/second

Question 15

Harry Hess (1906-1969) after WWII speculated the origin of the ocean floor. Why is the ocean floor lower than continents?

Answer 15

• density of basalt 3.3x density of water

- continents average about 2.8x the density of water

Question 16

Hess coined the phrase sea floor spreading, what is it?

Answer 16

When basaltic lava erupts on the sea floor, builds mountains along the mid ocean ridge, they then appear to move away over time. Also where basalt came in contact with sea water it became serpentine

Question 17

Prof. Fred Vine researched ocean floors and magnetic anomalies, what did he conclude?

Answer 17

Rocks on ocean floor were volcanic basalts, erupted from the mantle and there was a clear relationship between patterns of magnetic anomalies, ocean ridges and eruption of basalt

Question 18

Magma erupts, cooled and magnetised and then carried away by sea floor spreading. What happens when the Earths magnetic field switches?

Answer 18

New ocean floor erupts, cools but has reverse magnetisation

Question 19

Name 3 things drilling of the ocean floor discovered?

Answer 19

1. Symmetrical patterns of magnetic anomalies
2. New ocean crust added at a rate of 3.5km yr
3. Most of ocean crust younger than 200 million years old

Question 20

When did Europe and Africa begin to rift from America pulling Pangea apart?

Answer 20

During the Jurassic Period, (200-150 Ma) as sea level began to rise

Question 21

What developed across Britain and the North Sea?

Answer 21

Tectonic rift basins which were filled with warm shallow seas

Question 22

When did rifting reach it’s maximum in the North Sea?

Answer 22

150 milli years ago

Question 23

What did extensional tectonics across the North Sea produce?

Answer 23

A deepening basin, which trapped sediment. The sediment then compressed into shale, a type of rock

Question 24

What was rapidly deposted?

Answer 24

Marine mudstones, rich in organic matter, accumulated through rift basins, with deposits exceeding 3000m

Question 25

Upper Jurassic (165-150Ma) marine shales are important for what?

Answer 25

Petroleum source rock worldwide

Question 26

Conclusion: exploration of the ocean floor has bought together who changing the way we view the planet?

Answer 26

Oceanographers, geologists, biologists

Question 27

Conclusion: Ocean floor shown to be one of the most dynamic places on Earth, what does it affect?

Answer 27

The environment we live in

Question 28

Conclusion: What is still being made?

Answer 28

New discoveries