Tectonics: Earth's Structure + Plate Movement Theoretical Framework

Question 1

Describe the continent lithosphere 

Answer 1

Up to 70 km, thick, solid, less dense 2.8 g/cm³ Granite

O and S waves thro

Question 2

Describe oceanic lithosphere

Answer 2

Up to 7 km, thick solid denser 3.3 g/cm³. Basalt, P and S waves pass through 

Question 3

Describe the mantle

Answer 3

Solid but plastic with different densities made of periodite silica, rich Rock

P and S waves pass through a variable rates due to changes in density

Question 4

Describe outer core

Answer 4

Liquid, dense, 12% sulphur, 88% iron only P-waves past thro high temperature

Question 5

Describe inner core

Answer 5

Solid densest, hottest 20% nickel, 80% iron

only P waves reach the inner core and pass thro

Question 6

What heats up the inner core?

Answer 6

Residual heat and radioactive decay

Question 7

What three mechanisms move plates?

Answer 7

Convection current slab, pull ridge push

Question 8

How to convection currents occur

Answer 8

Core is hot and heats up surrounding magma which makes it less dense. This causes the rock or magma to rise as it rises it cools down, gets denser- as sinks it pushes against the plates, helping them move.

Question 9

What is slab pull?

Answer 9

As a plate subducts its weight pulls, the rest of plate along - the more that is subducting the greater the force of the pull

Question 10

What is ridge push?

Answer 10

As magma make its way to the surface and pushes through it separates and pushes against the surrounding plate

Question 11

evidence for continental drift - biological

Answer 11

fossil remains across continents e.g. mesosaurus fresh water species fossil remains in south afric and brazil - can’t have swam across salt sea

Question 12

evidence for continental drift -climatological

Answer 12

carboniferous limestone pennines and uk coal deposists need high temp and wet - fast decomp - suggests Eng was in tropics

Question 13

evidence for continental drift - geological

Answer 13

mount ranges across continents - Appalachian (NA) and Caledonian (Scandenavia and UK)

Question 14

what is the plate tectonic theory

Answer 14

earths surface is made up of plates which move relative to each other at diff speeds or directions. The boundaries btw plates are zone of tectonic activity like seismicity, vulcanity and mountain building

Question 15

Wadatti Benioff
Date
Idea
Significance

Answer 15

1920
EQ at Wadatti Benioff due to subduction - zone where plates no longer exist
Explains EQs

Question 16

Mantle Convection Current

Question 17

Evidence for seafloor spreading

Answer 17

Magnetic properties of the erupted basalt
earths magnetic field have been shown to flip occasionally so north and south pole swap
salts contains minute magnetic minerals and this changes directions depending on the earths magnetic field at the time of eruption 

Question 18

magnetic stripes

Answer 18

Polarity reversal from rock formations at the, mid-Atlantic ridge 

Question 19

Arthur Holmes, date, hypothesis and critique

Answer 19

1927 British geologist, he suggested convection currents. As a reason for continental drift. He suggest a radioactive decay generate enough heat for convection currents. As mantle is not exact same temperature throughout. Heat not evenly distributed, causing a magma to sink and rise

Holmes taken seriously as he had no real evidence.

Question 20

Harry Hess theory, date, evidence and hypothesis and critique

Answer 20

1961 seafloor spreading hypothesis

Using naval submarine detection technology recorded young age is four pieces on or near ridges are much older ages for ocean rock near the continental masses began to theorise that made ocean ridges. Mark structurally weak spots are in the ocean floor is being pushed to either side, new magma from deep within the Earth rises easily for this weak spots and eventually creates new seafloor

Critique is if new ocean floor is continually being made, why has earth not expanded

Question 21

Frederick, Vine and Drummond, Matthews, date, theory and significance

Answer 21

1963 theory of palaeomagnetism repeated reversals of earths magnetic field

as underwater volcanic, eruption occurred and the basaltic lava entries intrudes crust during the cooling process process. Particles of iron oxide align themselves along the earths magnetic field, which provides a permanent record of the polarity at the time which alternates approximately every 200,000 400,000 years creating a series of magnetic stripes with rocks aligned. this can be used to age the rocks

deep ocean trenches cut across existing magnetic anomalies. The boundary between the ages of lithosphere suggest that older or denser oceanic crust subducts, which provides an explanation to Hess’s greatest critique.

Question 22

Tuzo Wilson, date, theory and significance

Answer 22

Propose the Conservative plate Boundry - fault slips, horizontally, connecting oceanic ridges divergent plate, boundaries to ocean trenches of convergent boundaries. They were consider the last puzzle of the tectonic theory .

Explained the earthquakes and tectonic activity is that occur around these plate boundaries.

Question 23

Dan McKenzie year and contribution

Answer 23

Professor Vidya, physics and University of Cambridge, 1966,

use mathematical evidence to back up the theory

McKenzie modeled generation of magma at both mid ocean ridges and mantle plumes and helped us understand factors controlling partial, melting and

used knowledge of math physics and thermodynamics to understand the mechanisms for Earth cast movement.