Lec 3: Plate Tectonics

Question 1

The Earth’s evolution is divided into time periods. What are these based on? What do they correspond to?

Answer 1

The time periods are based on fossil/rock record. They correspond to changes in Earth’s climate, surface, or life forms.

Question 2

How are absolute dates determined?

Answer 2

From radiometric dating of IGNEOUS rocks.

Question 3

How is relative dating determined?

Answer 3

From the relationship between rocks

Question 4

What are the 3 types of rocks and what do they tell us about dating?

Answer 4

• igneous: cooled magma. Allow us to date most accurately, give us ABSOLUTE dates.
• sedimentary: formed from chemical precipitates or fragments of earlier rocks. Tell us about the relative ORDER in which events occured.
• metamorphic: formed from the application of heat or pressure to igneous or metamorphic rocks.

Question 5

radiocarbon dating works for things up to …. years old

Answer 5

50 000 years old

Question 6

How does radiometric dating with carbon work?

Answer 6

C-12 and C-13 are both stable carbon isotopes. C-14 on the other hand is unstable, meaning it decays for up to 50 000 years. By measuring the amount of C-14 in a rock, we can determine its age. Less C-14 = older rock.

Question 7

How do we determine the absolute age of rocks that are older than 50 000 years old?

Answer 7

Minerals within the rocks contain small amounts of unstable isotopes. By measuring the decay of these elements we can determine their absolute age. Measure ratio of radioactive parent to stable daughter isotopes.

Question 8

What is the Principle of Superposition?

Answer 8

newer sediment is continually deposited on top of previously deposited sediment.

Question 9

In which type of rock are fossils most abundant?

Answer 9

Marine sedimentary rocks

Question 10

Can we use the thickness of sedimentary layers to estimate how much time a layer represents? Why?

Answer 10

No.

• sediment accumulation is slower in the deep-sea
• storms can remove meters of sediments on beaches
• rocky coasts may see very little sediment accumulation

Question 11

When did Earth form? What did it form out of?

Answer 11

4.54 billion years ago out of a solar nebula

Question 12

What is the Goldilocks Zone?

Answer 12

The habitable zone around a star. From Earth to Mars.

Question 13

What was Earth like during the Hadean Eon (4.5 to 4 Ga ago)

Answer 13

• molten
• constantly bombarded by asteroids and comets
• the moon was formed when a small planet collided with Earth

Question 14

How was the Earth’s core created?

Answer 14

Earth was bombarded by smaller bodies, heating the Earth. Gravitational contraction also heated Earth. The Earth thus melted, and the heavier, iron-rich fraction of this liquid settled at its center.

Question 15

What was Earth like 4.4 Ga ago?

Answer 15

• It had a core, mantle, and crust.
• core = solid iron
• outer core = liquid iron
• mantle = partly melted magma
• maybe thin skin of solid rock

Question 16

What was Earth like by the end of the Hadean (4 Ga ago)?

Answer 16

• Earth cooled enough that rocks + oceans began to form
• steam in atmosphere cooled + fell, created oceans
• first continents begin to form

Question 17

What is the Archean eon associated with?

Answer 17

Life and plate tectonics!

- liquid water is prevalent

Question 18

What is the plate tectonics theory?

Answer 18

Idea that the Earth’s crust floats atop a liquid mantle.

Question 19

Who proposed the continental drift theory?

Answer 19

Alfred Wegener in 1915

Question 20

Describe the Earth’s structure.

Answer 20

1) Core
- inner core is solid, outer core is liquid and source of magnetic field
- rich in iron (unlike Jasmine)

2) Mantle
- behaves plastically
- rich in silicon and oxygen

3) Crust
- rich in silicon and oxygen

Question 21

What are tectonic plates made up of?

Answer 21

crust + upper mantle

Question 22

What are the different kinds of crust on Earth?

Answer 22

1) Oceanic
- thin, dense, young
- more iron

2) Continental
- thick, buoyant (less dense), old

Question 23

Which type of crust sinks under the other?

Answer 23

Oceanic crust sinks under continental crust

Question 24

What are differences in crust densities due to?

Answer 24

chemical differences

Question 25

What causes plates to move?

Answer 25

convection currents in the mantle

Question 26

Do plate boundaries correspond to continent boundaries?

Answer 26

no.

Question 27

Where can divergent boundaries occur?

Answer 27

They can form WITHIN continents. They produce rifts. New crustal material forms oceanic crust.

Question 28

Where do most active divergent plate boundaries occur?

Answer 28

Between oceanic plates, called mid-oceanic ridges.

This is called seafloor spreading.

Question 29

What is the longest mountain range in the world?

Answer 29

the Mid-atlantic ridge

Question 30

What are the 3 types of plate collision?

Answer 30

• continent-continent
• continent-oceanic
• oceanic-oceanic

Question 31

What does continent-continent collision create?

Answer 31

Very large mountain ranges!

Both plates are too buoyant to be subducted.

Question 32

What does continent-oceanic collision create?

Answer 32

Mountain range on continental plate + trenches!

Denser oceanic plate is subducted

Question 33

What do transform boundaries do?

Answer 33

result in earthquakes, creating faults.

Question 34

How have plate tectonics promoted the biodiversity of organisms?

Answer 34

changes in biotic and abiotic factors create new habitats and eventually new species.

Question 35

Are the evolution of life and the evolution of Earth connected?

Answer 35

Yes!