Tectonic Questions

Question 1

What are the continental and oceanic crusts made up of?

Answer 1

Continental - SIAL (Silicon and Aluminium)

Oceanic - SIMA (Silicon and Magnesium)

Question 2

How thick is the mantle?

Answer 2

2900km

Question 3

Why isn’t direct observation of the inside of the earth just not possible?

Answer 3

Due to its depth and temperature

So mainly use man made blasts and seismic waves to distinguish the layers

Question 4

What are convection currents?

Answer 4

The transfer of heat in a gas or liquid is a circular motion

Question 5

Name 3 researchers and their ideas on the structure of the earth

Answer 5

1620 - Francis Bacon: recognised ‘easy fit’ of South Africa and South America
1692 - Edmond Halley: suggested the earth was like a Russian nesting doll, each layer habitable
1912 - Alfred Wegener: theory of continental drift

Question 6

What types of evidence is there and what are the developments?

Answer 6

Evidence: bio, geo, climate
Developments: nuclear submarine mapping, Ewing and Tharp 1948, Harry Hess, paleomagnetism

Question 7

How does the discovery of the mid-ocean trench support plate tectonic theory?

Answer 7

Mid ocean ridges show the earth is spreading, but it would suggest the earth is getting bigger, but trenches show that crust is also destroyed

Question 8

What explains oceanic plates’ young age?

Answer 8

They are constantly being formed and created at mid ocean ridges and mid ocean trenches, due to their high density (3.0g/cm3)

Question 9

How fast do plates move?

Answer 9

Plates are continuously moving relative to each other, varying between 2-16cm a year

Question 10

What is a plate?

Answer 10

An irregularly shaped raft which floats on the asthenosphere and is succumb to convection currents below

Question 11

What are a lot of earthquakes caused by?

Answer 11

Because the earth is neither shrinking nor expanding, if new crust is created, it must be compensated somewhere by subduction = EQ

Question 12

What kind of volcanoes exist at constructive (o-o) plate boundaries?

Answer 12

Gentle, basic eruptions

Question 13

Explain the cause of transform faults

Answer 13

As plates either side of the mid ocean ridge move apart, they do not do so in an uniform way, so pressure mounts and fractures the ridge, forming transform faults which are perpendicular to the plate margin below
- may widen and deepen over time

Question 14

Example of submarine ridge which has become a volcano and eventually land

Answer 14

Surtsey Island, Iceland

N. American and Eurasian plate moving apart

Question 15

Example of plates causing rift valleys

Answer 15

African plate and Arabian plate forming the Great African Rift Valley
If plates continue to diverge, the resulting horst and graben landscape may eventually drop below sea level, creating a new ocean

Question 16

How long is the San Andrea Fault System? Where does it run through?

Answer 16

1300km

Cuts through most of California (6th richest economy in the world)

Question 17

Which plates are the cause of the San Andreas Fault System?

Answer 17

Pacific plate and N American plates are slowly grinding past each other in a NW direction, forming powerful EQ

Question 18

How is the San Andreas Fault System observed?

Answer 18

San Andreas Fault Observatory (SAFOD) makes an attempt to understand the complex system. They’ve drilled a ‘L-shaped’ hole in the fault line, filling it with thermometers, seisometers and other sensitive equipment to help monitor and understand, potentially even predicy

Question 19

What are long term effects of the San Andreas Fault System?

Answer 19

Constant rebuilding and replanning, must avoid building on mud and sand

Question 20

What kind of eruptions do destructive (o-o/o-c) plates have?

Answer 20

Explosive, andeisitic eruptions

Question 21

Example of o-c fold mountains, ocean trench, volcano and EQ

Answer 21

Fold mountains: Andes
Ocean trench: Peru-Chile trench in the Pacific coast of S America

EQ: Intermediate (30-70km) and deep (30-70km)