Lecture 4- Marine Geology

Question 1

origin of life on earth- 4 billion years ago

Answer 1

first life on earth (ocean only)

Question 2

origin of life on earth- 3 billion years ago

Answer 2

oxygen atmosphere formed from the actions of bacterial photosynthesis in the ocean

Question 3

origin of life on earth- 550 million years ago

Answer 3

• Cambrian explosion

- first life on land

Question 4

origin of life on earth- 250 million years ago

Answer 4

• largest mass extinction

- first mammals and dinosaurs

Question 5

origin of life on earth- 65 million years ago

Answer 5

• asteroid impact

- end of dinosaurs, rise of mammals

Question 6

How many mass extinctions have there been?

Answer 6

5

Question 7

bathymetry

Answer 7

measurement of depth of water in oceans, seas, or lakes

Question 8

SONAR

Answer 8

sound navigation and ranging

Question 9

single beam sonar

Answer 9

creates TRACKLINE of bottom depth

Question 10

towed multi beam sonar

Answer 10

creates a HIGH RESOLUTION SWATH of the bottom depth

Question 11

multi beam sonar

Answer 11

creates SWATH of bottom depth

Question 12

Theory of Continental Drift (1915)

Answer 12

• proposed by Alfred Wegener

- was not well accepted because the forcing mechanism he proposed was wrong (tidal action of the moon)

Question 13

Plate Tectonic Thoery

Answer 13

accepted after “sea floor spreading” and “sea floor subduction” were discovered (correct forcing mechanisms)

Question 14

Earth’s composition: rigid outer crust

Answer 14

• thin and rigid

- floats on the mantle

Question 15

Earth’s composition: plastic upper mantle

Answer 15

• solid

- high temperatures cause the material to be ductile enough to flow on very long timescales

Question 16

paleobiography

Answer 16

Wegener noted that in addition to the apparent good fit of the continents, the fossil and mineral distribution made sense if the continents were joined together in the past

Question 17

mid-ocean ridges

Answer 17

discovered with WWII sonar

Question 18

magnetic anomaly

Answer 18

• proxy of geologic time, each anomaly can be assigned to a specific date
• provided strong evidence of seafloor spreading

Question 19

earth’s magnetic field

Answer 19

• is not that stable

- has gone many reversals over time

Question 20

paleomagnetism

Answer 20

strips of alternating magnetic polarity

Question 21

strong evidence that the ridge is slowly spreading away from the ridge in opposite directions

Answer 21

rock getting older symmetrically as you move away from the ridge

Question 22

deep sea trenches and associated seismic activity

Answer 22

helped to explain the eventual loss of ocean crust that was eventually formed at mid-ocean ridges

Question 23

convection

Answer 23

process in which hot molten rock rises to the surface at DIVERGENT boundaries

Question 24

subduction boundaries

Answer 24

• hot molten rock cools and become more dense at the surface

- cooled rock sinks and is pulled by gravity back into the mantle at these boundaries

Question 25

origin of life on earth- 2 billion years ago

Answer 25

first multicellular life (ocean only)

Question 26

Devonian

Answer 26

Age of Fishes

Question 27

origin of jaws

Answer 27

ca 450 Ma

Question 28

oldest known bone

Answer 28

ca 500 Ma